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U. S. DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 189.

B. T. GALLOWAY, Chief of Bureau.

THE SOURCE OF THE DRUG DIOSCOREA, WITH A

CONSIDERATION OF THE DIOSCOREil

FOUND IN THE UNITED STATES.

BY

HARLEY HARRIS BARTLETT,
Chemical Biologist, Drug-Plant Investigations.

Issued November 11, 1910.

WASHINGTON:
government printing office.

1910.

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[Continued on page 3 of cover.] i

180 I

U. S. DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 189.

B. T. GALLOWAY, Chief of Bureau.

THE SOURCE OF THE DRUG DIOSCOREA, WITH A

CONSIDERATION OF THE DIOSCOREJl

FOUND IN THE UNITED STATES.

BY

HARLEY HARRIS BARTLETT,
Chemical Biologist, Drug-Plant Investigations.

Issued November 11, 1910.

LIBRARY

NEW YORK
60TANICAL

qakden.

WASHINGTON:
government printing office.

1910.

V

BUREAU OF PLANT INDUSTRY.

Chief of Bureau, Beverly T. Galloway.
Assistant Chief of Bureau, G. Harold Powell.
Editor, J. E. Rockwell.
Chief Clerk, James E. Jones.

Drug-Plant, Poisonous-Plant, Physiological, and Feementation Investigations.

scientific staff.

Rodney H. True, Physiologist in Charge.

A. B. Clawson, Heinrich Hasselbring, C. Dwight Marsh, and W. W. Stockberger,

Physiologists.
H. H. Bunzel and James Thompson, Experts.
Carl L. Alsberg, H. H. Bartlett, Otis F. Black, Frank Rabak, and A. F. Sievers,

Chemical Biologists.
W. W. Eggleston, Assistant Botanist.
.\lice Henkel, S. C. Hood, G. F. Klugh, Hadleigh Marsh, G. F. Mitchell, Ivar

Tidestrom, and T. B. Young, Assistants.
G. Archie Russell, Special Agent.

189
2

LETTER OE TRANSMITTAL

U. S. Department of Agriculture,

Bureau of Plant Industry,

Office of the Chief,
Washington^ D. 6'., July 20, 1910.

Sir : I have the honor to transmit herewith, and to recommend for
publication as Bulletin No. 189 of the series of this Bureau, a manu-
script entitled " The Source of the Drug Dioscorea, with a Considera-
tion of the Dioscorere found in the United States," prepared b}^ Mr.
Harle}" Harris Bartlett, Chemical Biologist in the Office of Drug-
Plant Investigations, and submitted for publication by Dr. Rodney
H. True, Physiologist in Charge.

For many years there has been more or less confusion among crude-
drug dealers in regard to what plant should be considered the true
medicinal " Dioscorea." Although there is little real evidence that
our native species of Dioscorea differ much in their medicinal quali-
ties, some authors have expressed a marked preference for a rhizome
which is now very rare in the trade. It is here shown that there is
better historical precedent for the use of the rhizome now handled by
crude-drug dealers than for the form which of late has been preferred.

In carrying out this investigation Mr. Bartlett has found it neces-
sary to consult much material located in many herbaria, collections,
and museums. He was assisted very materially by drug specimens or
information furnished by Mr. Floyd Cole (Trade, Tenn.), Mr. H. E.
Ellis (St. Petersburg, Fla.). J. Q. McGuire & Co.' (Asheville, N. C),
Mr. Joseph Powell (Bristol, Tenn), Mr. E. W. Proctor (Cincinnati,
Ohio), and Vannoy & McXeill (North Wilkesboro, N. C). To the
following persons he is indebted for the use of herbarium specimens or
notes on geographic distribution: Mr. W. H. Aiken (Lloyd Library),
Prof. S. M. Bain (University of Tennessee), Mr. H. W. Barre (South
Carolina Agricultural Experiment Station), Mr. C. D. Beadle (Bilt-
more Herbarium), Prof. W, J. Beal (Michigan State Agricultural
College), Mr. Stewardson Brown (Philadelphia Academy of Natural
Sciences), Prof. W. A. Buckhout (Pennsylvania State College), Mr.
George H. Chapman (Massachusetts Agricultural Experiment Sta-
tion), Prof. Mel. T. Cook (Agricultural Experiment Station, Dela-

189

3

4 LETTER OF TRANSMITTAL.

ware College), Mr. C. C. Deam (Indiana State Board of Forestry),
Prof. R. J. H. De Loach (University of Georgia), Prof. K. H. Den-
niston (University of "Wisconsin), Mr. H. S. Fawcett (University of
Florida), Prof. E. M. Freeman (University of Minnesota), Prof.
H. Garman (University of Kentucky), Dr. H. A. Gleason (University
of Illinois), Prof. F. D. Heald (University of Texas), Mr. O. E. Jen-
nings (Carnegie Museum), Prof. F. E. Lloyd (Alabama Polytechnic
Institute), Mr. J. M. Macoun (Geological Survey of Canada), Prof.
L. H. Pammel (Iowa Agricultural Experiment Station), Mr. J. T.
Pennypacker (Delaware Natural History Society), Prof. G. M.
Eeed (University of Missouri), Prof. B. L. Robinson (Gray Her-
barium), Mr. A. D. Selby (Ohio Experiment Station), Prof. J. L.
Sheldon (University of West Virginia), Dr. J. K. Small (New York
Botanical Garden), Prof. E. A. Smith (Geological Survey of Ala-
bama), and Prof. William Trelease (Missouri Botanical Garden).
To all the above-named persons thanks are due for helpful coopera-
tion.

Respectfully, Wm. A. Taylor,

Acting Chief of Bureau.
Hon. James Wilson,

Secretary of Agriculture.

189

CONTENTS,

Page.

Taxonomic history of the Dioscorepe of the United States 7

Synopsis of the species of Dioscorea . 11

The drug Dioscorea 19

189 5

ILLUSTRATIONS

Page.
Fig. 1. Map of the southeastern portion of the United States, showing the

distribution of Dioscorea quaternata 12

2. Map of the eastern portion of the United States, showing the distribu-

tion of Dioscorea glauca 14

3. Map of the eastern portion of the United States, showing the dis-

tribution of Dioscorea paniculata and its variety glabrifolia 15

4. Reproduction of Plate 7, " Dioscorea villosa, " from King and Lloyd's

"Supplement to the American Dispensatory" 21

5. Rhizome of Dioscorea glauca. Mountain form from the summit of

House and Barn Mountain in Russell County, Va 22

6. Rhizomes of Dioscorea paniculata from Agricultural College, Ingham

Co., Mich 23

7. Rhizomes of Dioscorea paniculata, var. glabrifolia, from Glenndale,

Prince Georges Co., Md 24

8. Rhizome of Dioscorea glauca. Typical drug from South Portsmouth,

Greenup Co., Ky 25

189
6

B. P. I.— 591.

THE SOURCE OF THE DRUG DIOSCOREA, WITH A
CONSIDERATION OF THE DIOSCORE,^: FOUND IN
THE UNITED STATES.

TAXONOMIC HISTORY OF THE DIOSCOREiE OF THE UNITED STATES.

Dioscorea, an extensively, developed genus in the Tropics of both
hemispheres, is represented in the eastern and central United States
by five species. Of this number, two are described for the first time
in this paper; the others have had a long and involved bibliographic
history.

In 1705 Plukenet " published " Bryoniae nigrae similis floridana,
muscosis floribus quernis, foliis subtus lanugine villosis, medio nervo
in spinulam abeunte." In 1839 Gronovius '' referred Plukenet's
plant to Dioscorea, in the following account of a specimen which
Clayton had sent him from Virginia:

Dioscorea foliis cordatis acuminatis, nervis lateralibus ad medium folii
terminatis. Mas.

Bryoniae nigrae similis Floridana, etc. Plukn., Auialtb., p. 46, t. 375, f. 5.

Lupnli species late scandens, foliis cordiformilms venosis, alia tlore, alia
semine foecnnda, flores albos steriles in spica pendnla ferens, seminibns mem-
branis extantibus alatis, vasculo qnoque seminali membranaceo triquetro
inclusis, pluriniis in racemos ad modnm Lupulorum dense congestis. Clayt.
n. 94.

The only Dioscorea ascribed by Linnseus to the present area of
the United States Avas in part based upon the above citations from
Plukenet and Gronovius. He treated it as follows : "

7. Dioscorea [villosal foliis cordatis alternis opposltisque, caule laevi.

Dioscorea foliis cordatis acuminatis: nervis lateralibus ad medium folii
terminatis. Gron. Virg. 121.

Bryoniae nigrae similis floridana, muscosis floribus quernis, foliis subtus
lanugine villosis: medio nervo in spinulam abeunte. Pluk. Aim. 46, t. 375, f. 5.

Habitat in Virginia, Florida.

In attempting to decide upon the application of the name Dioscoi'ea
villosa, it was but natural to inquire whether there was any speci-
men so called in the herbarium of Linnaeus. Dr. B. Daydon Jackson,

« Amaltbeum, p. 46, t. 375, f. 5.
^ Flora Virginica, e<l. 1, p. 121.
"Species IMautarum, ed. 1 (1753), ii, p. 1033.

55838°— Bui. 189—10 2 7

8 THE SOUKCE OF THE DRUG DIOSCOKEA.

secretary of the Linna?an Society, very courteously looked into the
matter, and wrote as folloAvs:

On referring to the Linnsean lierbarium, I found only one American speci-
men. * * * At the bottom of the sheet is the note by Linne himself, " 6 K
sativa," to which Smith has added in pencil, " non est;" K = Kalm. I do- not
find any specimen named by Linne " villosa " in his herbarium, but as sativa
is an lOast Indian species, and the specimen is of Kalm's collection, it is patent
that there is a blunder.

Since Kalm is not mentioned in the treatment of Dioscorea villosa,
and since no localities but Virginia and Florida (these obviously
refer to the citations from Gronovius and Plukenet) are mentioned
by Linna'us, we can by no means typify D. villosa by the Kalm speci-
men." The species must therefore be interpreted in the light of the
diagnosis and synonymy given by Linnaeus.

Doctor Rendle, of the British Museum, has kindly sent a photo-
graph and description of the specimen which Clayton collected in
Virginia and sent to Gronovius. It is identical with the most widely
distributed Dioscorea of our range — not the most characteristic
species of Virginia, to be sure, but the one which would probably have
been collected in the coastal part of the State. In the matter of
pubescence the species varies considerably, but, according to Doctor
Rendle, the Gronovian specimen is glabrous except for puberulence
on the veins and venules of the lower leaf face. It can not, there-
fore, have been seen by Linnseus at the time he wrote the Species Plan-
tarum, for he would not have applied the adjective " villosa '" to an
almost glabrous plant. As a matter of fact, the specific name came
from Plukenet's " Bryoniae nigrae similis floridana, muscosis floribus
quernis, foliis subtus lanugine villosis, medio nervo in spinulam
abeunte." This characterization and the figure which accompanies
it are altogether vague, and in at least one point, the description of
the flowers as four parted, not even in accord with the generic
concept of Dioscorea. If we typify Dioscorea villosa by the
Gronovian specimen, as there is some warrant for doing because of
the fact that the first-cited locality in the Species Plantarum is
Virginia, we must call a widely distributed and abundant plant by
a name which is altogether inept. Richard'' found a way out of
this difficulty by renaming the northern plant, which is identical
with the Gronovian specimen. His treatment follows :

D. [paniculata] caule laevi foliis brevibus, cordatis, acuminatis, racemo masc.
e plurimis racemulis filiformibus quasi-paniculatim composite ; capsula rotun-
da ta glabra.

''A photograph of Kalm's specimen, kindly sent by Doctor Jackson, shows
that it should be referred to the species treated in this paper as Dioscorea
paniculata.

^Michaux, Flora Boreali-Americana (1803), ii, p. 239.
189

TAXONOMIC HISTORY OF THE DIOSCORE^ OF THE UNITED STATES. 9

D. villosa Liun.

D. quaieniata et quinata Gmel.
Obs. Cultura saepe fit glabra.
Hab. a Canada ad Cai'olinam.

There is no reason why the name Dioscorea panicvlata should not
be adopted, for the description and range implicitly exclude the
dubious jjlant of Plukenet.

The Vienna code provides for the rejection of names which are
likely to remain permanent sources of confusion and error. On this
ground the name Dioscorea villosa should surely be dropped. The
Linnanin diagnosis differs in only one word from that of Z>. saliva:

6. Dioscorea [sativa] foliis cordatis alternis, caule laevi.

7. Dioscorea [villosa] foliis cordatis alternis oppositisque, caule laevi.

Moreover, the single character which Linnaeus used to distinguish
his Dioscorea villosa from his D. sativa (leaves, in the former species,
alternate a>id opposite) did not apply either to Plukenet's plant or to
that of Gronovius. The Gronovian specimen at the British Museum
has all the leaves alternate. The sheet bears this annotation : " Hinc
inde folia fert opposita, unde potius dicenda Dioscorea foliis cordatis
alternis oppositisve." Plukenet's plate shows no opposite leaves. As
Lamarck" pointed out in the passage ouoted below, the character
" foliis oppositis '' had a bibliographic origin with Plumier and Rum-
phius, whose Polygonatum scandens cdtissinium^ foliis Tainni and
Uhium niimmidarium are included by Linna?us in Dioscorea villosa^
although he does not cite them.

Je crois qu'une Iguame dont les feuilles sont les unes alternes & les autres
opposees, est un etre de raison ; que Linne a'a etabli son Dioscorea villosa que
sur les livres, eu voulant faire regarder conime la meme plaute le Bnjoniae
nigrae siinilis Floridana de Phikenet. le Polygonafum scandens alfissi)ni(m . . .
de Plumier, enfin VUbiiim nummiUarimn de Rumplie, qui sont trois plantes
tres-differentes eutr'elles. Mais la plante de Plukenet n'a aucuues feuilles op-
posees, constatees par I'observation ; au contraire, celle de Plumier, que j'ai
vue. & que je decris ci-dessous, n'a aucunes feuilles alternes. Quelle est done
cette Iguame de la Virginie & de la Floride, qui a en meme temps des feuilles
opposees & des feuilles alternes? Je n'en trouve aucun indice, soit daus les
livres, soit dans les Herbiers que j'ai pu visiter. Au reste, la figure citee de
Plukenet (t. 375, f. 5), ressemble beaucoup a la plante que Ton cultive au Jardiu
du Roi sous le nom de Dioseorea sativa, plante qui y subsiste eu plelne terre,
sans que la gelee fasse perir sa racine, ce qui me fait presumer que cette meme
plante n'est point des Indes, mais qu'elle est reellement originaire de la
Virginie.

Wliile Linnaeus was writing the Species Plantarum, Burman was

engaged in editing works of Rumphius * and of Plumier.'" An ap-

° Encyclopedie Methodicpie P>otanique, iii (1789), p. 231.

^Rumpbli Herbarium Amboinense (1741-1755).

<^P]Mntarum Americanarum fasciculus (I, II . . . etc.), continens plautas
quas olim Carolus Plumierius detexit, eruitque atque in lusulis Antillis ipse
depiuxit (1757).
189

10 THE SOURCE OF THE DRUG DIOSCOREA.

pendix " to the Herbarium Amboinense contains an " Index univer-
salis," in Avhich Uhium nuTmnular'mm is referred to Dioscorea villosa.
In his preface Burman states that the Linnsean references were
taken from a dissertation published by Stickman under the direction
of Linnaeus in 1754, and therefore contemporaneous in preparation
with the Species Plantarum. The dissertation was reprinted in the
Amoenitates Academicae.''

The evidence that Plumier's Polygonatum scandens aUissimum^
foliis TaTYini is included in the Linna^an concept of Dioscorea mllosa
is not so convincing as in the case of Uhhim nummjulanKm. The two
plants are made synonyms in Burman's edition of Plumier, but
whether or not with the knowledge of Linnaeus it is impossible to say.
Plumier's plate is of an opposite-leaved Dioscorea from the West
Indies, a member of a section of the genus to which our species have
no resemblance.

As compared with Dioscorea villosa^ none of our other species are
difficult of interpretation. Walter'" published Anonymos (Dios-
coreae affinis?) quaternatus, foliis cordatis septemnerviis, nervorum
pari extimo bifido, acuminatis, infimis quaternis deinde ternis binis
alternisque, caule sinistrorsum volubili, racemis axillaribus pendulis,
floribus sursum assurgentibus, and Anonymos (Dioscoreae affinis?)
quinatus, foliis peltato-cordatis, 9-nerviis, foliis infimis quinis.
Gmelin** later copied the diagnoses and published the binomials
Dioscorea quaternata and D. quinata. Walter's herbarium, at the
British Museum, contains specimens of neither plant. Dioscorea
quaternata was accepted as a good species by Pursh,'' Nuttall,^
Elliott," Beck,'' and Kunth,^ and is interpreted in the traditional
way in this paper. D. quinata^ on the other hand, has always been
an enigma.

In 1813 Muhlenberg ■' published Dioscorea glauca^ a nomen subnu-
dum. Fortunately, however, his plant is as readily identified from
the descriptive name which he chose, and from tlie locality, as though

» Rnmphii Herbarii Amboinensis Auctuarium (1755).

^ Amoenitates Acacleuiicae, iv. Diss. Ivi, Herbarium Amboinense sub praesidio
D. D. Car. Liunaei proposuit Olavus Stickman. Upsaliae, 1754, ]Maj. 9.
c Flora CaroHniana (1788), p. 246.

•^ Linnaei Systema Yegetabiliuni, ed. 13 (1791), i, p. 581.
« Flora Americae Septentrional is (1814), i, p. 251.
f Genera of North American Plants (1818), ii, p. 238.
s' Botany of South Carolina and Cxeorgia (1824), ii, p. 704.
''Botany of the Northern and Middle States (1833), p. 355.
^ Enumeratio Plantarum (1850), v, p. 336.
i Catalogus Plantarum Americae Septentrionalis (1813), p. 92.

189

SYNOPSIS OF THE SPECIES OF DIOSCOKEA. 11

he had written a full description. He recognized two species, which
he treated as follows:

Dioscorea : (1) villosa 2/ bairy Pens. fl. Jim. Virg; (2) glauca 1/ glaucous
Peus. tl. Jun.

Only two species have been found in a large series of specimens
from Pennsylvania. One of them, Dioscorea paniculata, corresponds
to the D. villosa of Muhlenberg, and the other must therefore be
called D. gJauca. There is nothing to represent Muhlenberg's name
in his herbarium at the Philadelphia Academy of Natural Sciences,
but there can not be the least doubt that it has been applied to the
correct plant.

Rafinesque " described four Dioscoreae in 1830. Two of them
D. megaptera and D. hexaphylla may be referred to D. glauca, and
one, D. repanda, may be divided between D. glaiica and D. quater-
nata. The other, D. longifolia^ described from leaves only, it is im-
possible to identify.

In 1850 Kuntli '' jDublished Dioscorea pruiiiosa. No specimen is
preserved at Berlin. From his full description, however, it seems
clear that the plant should be referred to D. glauca.

Between the years 1850 and 1909 all of our Dioscoreae were treated
in botanical works as one species under the name Dioscorea villosa.
In the seventh edition of Gray's Manual (1909) the editors departed
from current usage in taking up D. villosa var. glabra^ a name ob-
scurely published by Mr. C. G. Lloyd in 1880,"" and afterwards used
in various medical works.*^ Careful study of all the evidence available
has shown that this name is likewise a synonym of Dioscorea glauca.
Mr. Lloyd's very valuable observations on the medicinal rhizomes of
the two plants distinguished by him as D. villosa and D. villosa var.
glabra will be given due attention in another connection.

SYNOPSIS OF THE SPECIES OF DIOSCOREA.

Staminate inflorescences solitary and occurring only in the leaf axils.
Lower leaves verticillate in 4"s to 7's.

Leaf blades green below when mature, usually glabrous,

1. D. quatemata.
Leaf blades glaucous below when mature, generally hirtellous,

2. D. glauca.

"New Flora of North America, second part, Neophyton (1836), pp. 88-89.

^Enumeratio Plantaruni, v. (1850). p. 330.

'^ King, John, and Lloyd, John Uri, Supplement to the American Dispensatory
(1880), pp. 81-83.

^ Several editions of King's American Dispensatory, revised by H. W. Felter
and J. U. Lloyd.

A Treatise on Dioscorea and Sulphurous Acid. Drug Treatise No. 14, issued
by Lloyd Brothers (1905).
189

12

THE SOUECE OF THE DRUG DIOSCOREA.

Lower leaves all alternate, or the three lowest subapproximate or verticillate.
Internodes strictly glabrous. Fruiting racemes many fruited.

Leaves pubescent beneath 3. D. paniculata.

Leaves altogether glabrous 3. D. paniviilaia gUibrifoIia.

Internodes hairy. Fruiting racemes 1 to 4 fruited 4. D. hirticauUs.

Staminate inflorescences solitary or fasciculate in the leaf axils, and termi-
nating the stem 5. D. floHdana.

1. Dioscor(xi quaternata (Walt.) Gmel. Rhizomes about 1 cm. in
diameter, straight or sometimes forked, with few or no short lateral
branches. Stems 1 to 2 m. long, rigid and erect below the first node,
requiring support above. Lower leaves verticillate by 5's or 6's

Fig. 1.— Map of the southeastern portion of the United States, showing the distribution of

Dioscorca quaternata.

(rarely 4's or T's) ; upper leaves alternate. Petioles of the lower
leaves densely pubescent at base and apex, sometimes glabrate in age.
Leaf blades cordate, repand, green on both sides, usually strictly
glabrous except for the dense pubescence at the insertion of the
petiole. Staminate inflorescences paniculate, solitary in the leaf
axils, occuring even in the axils of the lower verticillate leaves.
Pistillate inflorescences few flowered. Fruit 2 to 3 cm. long, very
variable in shape.

The distribution of this species, as shown in figure 1, is based upon
the following material :

189

SYNOPSIS OF THE SPECIES OP DIOSCOREA. 13

North Carolina. — Guilford County, Biltmore Herb., 364 a ; Orange County,
W. W. Ashe; Swain County, H. C. Beardslee and G. A. Kofoid, July 25, 1S91.

South Carolina. — Oconee County, H. D. House, 3470 and 2120 ; Pickens
County, //. D. House, 3079.

Georgia.— De Kalb County, H. Eggcrt, May 22, 1897, and W. W. Ashe, May,
1896; Floyd County, Chapman Herb.; McDuffie County, H. H. Bartlett, 1722
and 1733 ; Walker County, Percy Wilson, 197 ; Meriwether County, S. M. Tracy,
9208.

Alabama. — Bibb County, E. A. Smith, July 20, 1879 ; Cullman County. //.
Eggert, June 21, 1897, and C. P. Baker, May 18, 1897 ; Hale County, S. Watson,
in 1857 ; Lee County, F. S. Earle and C. F Baker, April 24, May 8, and October
2, 1897 ; Montgomery County, C. Mohr; Tuscaloosa County, E. A. Smith, 1287
and 1516 ; Wilcox County, 8. B. Buckley, May, 1839.

Florida. — Franklin County, Chapman.

Louisiana. — East Baton Eouge Parish, W. R. Dodson.

Mississippi. — Choctaw County (?), /. M. Cliite, 68; Jones County, 8. M. Tracy,
3355 ; Smith County, S. M Tracy, August 22, 1903.

Arkansas. — Garland County, William Trelease, October 3, 1898, and 8. E.
Meek, August 19, 1889 ; Independence County, F. V. Coville, ISO ; Pulaski
County, H. E. Hasse, April 11, 1886.

Missouri. — Jefferson County, H. Eggert, July 15, 1892.

Tennessee. — Franklin County, A. Gattinger; Hamilton County, F. Lamson-
Scribner, May 21, 1890; Haywood County, S. M. Bain, June 13, 1893; Knox
County, A. Ruth, 779 and 1200 a ; Monroe County, F. Lamson-Scribner, June 29,
1890.

Kentucky. — ^Lyon County, IF. W. Eggleston, 4674.

2. Dioscorea glauca Mulil. Rhizomes 1 cm. or more in diameter,
often forked and with many short lateral branches equal in diameter
to the rhizome, usually much contorted and forming dense masses.
Stems 1 to 3 m. long, rigid and erect below the first node, requir-
ing support above. Lower leaves verticillate in whorls of 5 to 7;
upper leaves alternate. Petioles densely pubescent at the apex.
Leaves larger than in D. quaternata.^ less markedly repand or not at
all so, usually sparsely hirtellous beneath, but often glabrous, always
glaucous when mature. Paniculately branched staminate inflores-
cences solitary, occurring in all the leaf axils. Pistillate inflores-
cences few flowered ; fruits 2 to 3 cm. long.

Dioscorea glauca is essentially a plant of the mountains, although
in the northern part of its range it is found near sea level. In the
lowlands southward it is replaced by the closely related D. quater-
nata. As will be seen from the map (fig. 2) the ranges of the two
species hardly overlap.

The following specimens have been examined:

Pennsylvania. — Allegheny County, J. .4. Shafer, 590, and C. C. Mellor, June
7, 1889 ; Fulton County, Witmer Stone, June 4, 1905 ; Huntingdon County, O. E.
Jennings, May 17, 1904 ; Lancaster County, J. J. Carter, May, 1870, and A. A.
Heller, June 5. 1900; Susquehanna County, A. Stengel, May 29, 1886; West-
moreland County. O. E. Jennings, May 19, 1904 ; York County, J. N. Rose and
J. H. Painter, 8123.
189

14

THE SOURCE OF THE DEUG DIOSCOEEA.

Delaware. — Newcastle County, William M. Canhy, July, 1893.

Maryland. — Garrett County, G. A. Eifrick, May. 1902; Montgomery County,
A. CJia.sc. 2313 and 2827*, and H. H. Bartlett, 1821 ; Prince Georges County, A.
Cliasic, 2215; District of Columbia, E. S. Steele, 67, and H. D. House, 709.

Virginia. — Alexandria County, A. 8. Hitchcock, September, 1904, and L. H.
Dewey, 239; Bedford County, A. H. Curtiss. 43953; Campbell Coimty, 8. B.
Buckley; Fairfax County. E. L. Morris, June. 1896, and L. H. Dewey, 232;
Loudoun County, A. Chase, 2244; Russell County, C. L. Alsberg, 54 and 120;
Smyth County, -/. K. Small, June 4, 1892.

West Virginia. — Barbour County, J. M. Oreenman, 93; Monongalia County,
O. E. Jcnmngs, July 4, 1909; Preston County, J. L. Sheldon, 1454, and E. S.
Steele, August 18, 1898; Upshur County, W. M. Pollock, May 30. 1895. and May
31 and June 12, 1897.

Fig. 2. — Map of the eastern portion of the United States, showing the distribution of

Dioscorca glauca.

Ohio. — Hamilton County, C. G. Lloyd.

Illinois— Vnion County, E. S. Earle, 763, and Mrs. C. Butler, August 13. 1880.

Kentucky. — Fayette County, W. A. Kellerman, in 1882; Greenup County, John
Butler, in 1909: Jessamine County, H. Garman; McCracken County, Biltmore
Herb., 364 c; Menifee County. //. Garnmn, May 8, 1893; Pulaski County, V. W.
Mathews, July 11. 1892; Warren County, S. F. Price, May 21, 1900; Wolfe
County. M. L. Didlake, June, 1898.

Missouri.— ^t. Louis County, 'N. M. Glatfelter (?), 517.

Tennessee. — Knox County, F. Lamson-Scribncr, May 14, 1SS9.

North Carolina. — Buncombe County, Biltmore Herb., 364, and F. Crayton and
W. W. Eggleston, 4398; Macon County. L. R. Gibbs, in 1881; Orange County,
W. W. Ashe, June, 1898; Polk County, J. R. Churchill, May 30, 1899, and E. C.
Townsend, April 29, 1897 ; Surry County, H. H. Rusby, June 18, 1909.

South Carolina.— AxiAavson County, L. R. Gibbs, In 1885; Oconee County,
A. P. Anderson, 1502.
189

SYNOPSIS OF THE SPECIES OF DIOSCOREA.

15

3. Dioscorea paiiiculata Michx. Rhizomes long and slender, simple
or rarely forked, less than 1 cm. in diameter, with a few short lateral
branches of less diameter. Stem 1 to 4 m. long, flexucns, glabrous.
Leaves all alternate, or two or three of the lowest subapproximate,
pubescent or puberulous beneath. Petioles glabrous at the insertion
of the blade, or, if pubescent, less densely so than the blades. Stami-
nate inflorescences solitary, borne only in the leaf axils of the upper
half of the stem, the three or four lowest less branched than those
higher up. Pistillate inflorescences densely many fruited. Capsules
2 cm. long or less.

Fig. 3. — Map of the eastern portion of the United States, showing the distribution of
Dioscorea paniculata (liy dots) and its variety glabrifolia (l\v crosses).

Var. glabrifolia Bartlett.*^ Leaves altogether glabrous. This va-
riety replaces the typical form of the species in the southwestern part
of the range. Various northeastern specimens are indistinguishable
from the southwestern plant, but may be genetically distinct from it.
In the distribution map (fig. 3) the range of the variety is shown by
crosses.

"• Dioscorea paniculata glabrifolia var. nov. Foliis glabris exceptis, forniae
specie! typicae omnino siniilis. A. 8. Hitchcock, 830 (pro parte) "Woods,
Cherokee Co., Kansas, 1896."
189

16 THE SOURCE OF THE DRUG DIOSCOREA.

The following specimens of Dioscorea paniculata have been ex-
amined : "

Connecticut. — Fairfield County, C. L. Pollard, 115; Middlesex County, J. II.
Redflchh 7952, and S. B. BncMcy, September, 1835; New Haven County, 0. II.
Bissell, 203, and A. L. Winton, July 8, 1886 ; New London County, G. R. Lums-
dcti, July 16, 1885.*

New York. — Chemung County, T. F. Lucy, 712; New York County, N. L.
Britton, July 22, 1879; Tioga County, F. V. Covillc. June 4, 1887, and F. E.'
Fenno, 401 ; Westchester County, G. V. Nash, July 2, 1896.

New Jersey. — Atlantic County, C. A. Gross; Bergen County, N. L. Britton,
September, 1883; Camden County, E. B. Bartram, August 3, 1907; Hudson
County, A. C. Hexamcr and F. W. Maier, August 17, 1852, and William M. Van
l^icMe, July 1, 1894; Ocean County, J. II. Grove, July 16 and August 21, 1908;
Passaic County, G. V. Nash, July, 1889; Warren County, Albrecht Jahn, Sep-
tember 14, 1895, Thomas C. Porter and A. A. Tyler, June 27, 1896.

Delaware. — Newcastle Countj% A. Commons, July, 1866.

Maryland. — Allegany County, Howard ^Iirirer, in 1894; District of Columbia,
F. Blanchard, September 17, 1890, L. F. Ward, July 8, 1878, and C. L.^Pollard,
G05.

Pennsylvania. — Bucks County, Bayard Long, July 6, 1909 ; Center County,
W. A. Buckhout, October, 1909; Crawford County, O. E. Jennings, August 19,
1904, and J. A. Shafer, July 23, 1901 ; Dauphin County, J. K. Small, July 18,
1888; Delaware County, >S'. S. Van Pelt, June 24, 1906; Franklin County, /. A.
Keller, July 28, 1895; Lebanon County, J. K. Small, December, 1891; Lehigh
County, A. F. K. Krout, June, 1878; Monroe County, Joseph Craivford, July 4,
1896; Montgomery County, Alexander MacElivee, June 26, 1892; Northampton
County, A. A. Tyler, 550, and Bayard Long, June 29, 1908; Philadelphia
County, J. II. Redfleld, 7951.

Ontario. — Essex County, Macoim, July 24, 1892; Lincoln County, IF. C.
McCalla, 244 ; Welland County, Cameron, August, 1892.

Ohio. — Franklin County, E. B. Williamson, June 22, 1897 ; Hamilton County,
C. G. Lloyd, June 25, 1890, and IF. H. Aiken, June 15, 1902: Lucas County,
Lewis Schults, 1705; Richland County, E. Wilkinson, 10214; Sandusky County,
M. J. Persing, July 10, 1897 ; Summit County, L. D. Stair, June 26, 1896; Wayne
County, -4. Russ, 435, and -1. D. Selby and J. W. T. Dnvel, 4.36.

Michigan.— V,Yi\\\Q\\ County, J. Shaddick, July 29, 1896; Cass County, //. S.
Pepoon, 452; Genesee County, D. Clark; Gratiot Countj-, C. A. Davis, July 10
and October, 1892; Ingham County, C. F. Wheeler, June 20, 1895; Ionia
County, F. P. Daniels, June, 1896; Jackson County, Houghton, July 13, 1S38;
Kalamazoo County, Houghton, August 2, 1838; Kent County, .4. A. Crozier,
July 11. 1886; Lenawee County, W. J. Beat, in 1886; Muskegon County, C. D.
McLouth, September 7, 1898; Shiawassee County, G. H. Hicks, July 13, 1889;
Washtenaw County, Houghton, July 2, 1838; Wayne County, William Boote,
June 26, 1871.

Wisconsin. — Dane County, H. L. Russell, June 20, 1887, and L. S. Cheney,
July 5, 1890; La Crosse County, L. II. Pammel, July, 1887; Lafayette County,
L. 8. Cheney, June 26, 1890; Wood County, B. M..Vaughan, July, 1883.

"The occurrence of Dioscorea paniculata in Middlesex County, Massachusetts,
shown in figure 3, is based upon Bigelow's report of tlie plant as "rare" in
"woods on the Concord turnpike." (Florula Bostoniensis, 2d ed., 1824, p. 369.)
It has not been reported since.

* Of all the specimens cited in this synopsis, only this one had branched
pistillate inflorescences.
189

SYNOPSIS OF THE SPECIES OF DIOSCOREA. 17

Minnesota. — Chisago County, B. C. Taylor, August, 1S92 ; Olmsted County,
Mrs. George AinsUe, May 28, 1895; Washington County, H. Eggert, July 12,
IS'92; Winona County, J. M. Holzinger, August 21, 1888.

Indiana. — Allen County, C. C. Deam, 1157; Blackford County, C. C Deam,
1101: Grant County. C. C. Deam, 2177; Huntington County, C. C. Deam, 2146;
Kosciusko County, C. C. Deam, 3205; Noble County, C. C. Deam, 316; Parke
County. H. H. Bartlett, June 25, 1903 ; Posey County. C. C. Deam, 910 ; Steuben
County, C. C. Deam. June 16, 1903; Tippecanoe County, //. B. Dorner, July 4,
1901 ; Wells County. C. C. Deam, 4.

/////iois.— Champaign County, M. B. Walte. June 28, 1886; Cook County. A.
Chase, June 1, 1896; Dupage County, L. M. Umhach, August 18, 1897, June 16
and July 2, 1898; Henderson County, H. N. Patterson. 439.14; Marshall County,
T'. H. Chase. 14SS; Peoria County, F. E. McDonald, July, 1893; St. Clair County,
H. Eggert, June 24, 1875, and August 28. 1878 ; Stark County, V. H. Chase, 623 ;
Rock Island County, C. C. Parry. July, 1865; Vermilion County, M. B. Waite,
June 24, 1886.

Iowa. — Fayette County. B. Fink, 472; Henry County, ./. //. Mills, 531; Johnson
County, F it z pat rick, June, 1896; Pottawattamie County, F. V. Hayden, July 5,
1853; Scott County, C. C. Parry; Story County, A. 8. Hitchcock; Winneshiek
County, E. W. D. Holway, June 30, 1882.

Missouri. — Boone Couuty, F. P. Daniels, June 13, 1903; Caldwell County,
J. E. Totvnsend. September, 1869 ; Cole County, 0. Kraiise, June. 1867 ; Greene
County, J. ir. Blankinshii). 2477; Jasper County, F. J. Palmer, 527; Jefferson
County, H. Eggert. June 26, 1892; St. I.ouis County, H. Eggert. June 14. 1893.

Kansas. — Cherokee County, A. 8. Hitchcock, 830 (pro parte) ; Miami County,
J. H. Oyster.

Oklahoma.— District 2. Indian Territory, B. F. Bu.sh. 11.37.

The following specimens of the variety glahrifoUa hcive been
examined :

Connecticut. — Middlesex County, Sf. B. Buckley, September, 1835; New Haven
County, Robbins.

PeH».s-///rf/»i(/.— Philadelphia County, S. 8. Van Pelt. July 10. 1908.

Maryland. — Prince Georges County, //. H. Bartlett, 1873.

Tennessee. — Playwood County. S. M. Bain, 321.

Missouri. — Boone County. F. P. Daniels, June, 1903; Cass County, O. C.
Broadhead, June, 1865; Jasper County, B. F. Lutman, August 1, 1901, and E. J.
Palmer, 832 ; Saline County. William Trelease, June 23, 1886.

Kansas. — Cherokee County, A. 8. Hitchcock. 830 {pro parte).

Arkansas. — St. Francis County, William Trelease, August 20, 1897; Sebastian
County, J. M. Bigelow, in 1853-54.

Texas. — Harris County, J. F. Joor, June 20, 1877; Upshur County, J. Rever-
shon, 2497 and 4033,

4. Dioscorea hirticaulis Bartlett." Rhizome less than 1 cm. in
diameter, simple or rarely forked, nearly straight, bearing short lat-

^Dioscorea hirticaulis sp. nov. Rhizoma horizoutale, plerumque simplex vel
raro furcatum, usque ad 50 cm. longum, crassitudine ca. 8 mm. ; ranuilis panels
lateralibus abortivis quam rhizomate multo tenuioribus, 0.5-2 cm. longis;
caulium cicatricibus saepe inter se 10-12 cm. distantilius saepe binis trinisve
approximatis. Caulis gracilis scandens flexuosus 2-3-nietralis, hirtellus. Folia
infima 3 verticillata vel propinqua. superne alterna. laniinis eordatis 7-9 nerviis,
supra glabris subtus griseo-pubescentibus, margine saepissime repaudis ; petiolis.
189

18 THE SOURCE OF THE DRUG DIOSCOREA.

eral branches of 2 to 3 mm. diameter. Stem 1 to 3 m. long, flexuoiis.
weak, pubescent. Leaves all alternate, or the three lowest verticillate
or SLibapp)roximate, griseous-pubescent beneath and also, though not
so densely, on the apex of the petiole. Staminate inflorescences soli-
tary in the leaf axils of the upper half of the stem, the lowest simple
or with one branch, the others increasingly paniculate. Pistillate in-
florescences developing from 1 to 4 fruits, which are about 2 cm. long.

Dioscorea hirticaalis is probably confined to the region of the fall
line and to the Coastal Plain, for no stations are known further
inland. As it occurs about Thomson, Ga., it is confined to the branch
swamps, where its long rhizomes run horizontally barely beneath the
surface of the black muck soil. The only other Dioscorea of the
region, />. quaternata^ with which it shows not the least intergrada-
tion, has a totally different habitat.

Specimens examined : *

'North Carolina. — Cumberland County, Biltmore Herh.. 3G4 b.
Houth Carolina. — Berkeley County, //. W. Rarencl.
Georgia.— McDuffie County, H. 11. Bartlett, 14G8.

5. Dioscorea floridana^nvtlett.'' Ehizomes unknown. Stem flexu-
ous, twining. Leaves alternate, entirely glabrous, green above, paler
beneath. Staminate inflorescences paniculate, terminating the stem
and also fasciculate by twos and threes in the upper leaf axils, the
larger axillary inflorescences sometimes 40 cm. long. Pistillate in-
florescences solitary, 5 to 7 flowered. Fruits about 2 cm. long, similar
in shape to those of D. panicidata.

This species is very clearly distinguished from our other species
by the position of the staminate inflorescences. In material collected
by Mr. Harper in Georgia the larger inflorescence of an axillary
fascicle exceptionally bears one or two leaf -like bracts. As at the end

praecipue ad apicem versus, hirtellis. Inflorescentiae masculae solum in
foliorum axillis superiorum positae, densiflorae, inferiores vix ramosae, su-
periores paniculatae; pedunculo perbrevi ramulisque sub lente pubescentibus,
alato-angulatis. Perigonium 6-partitum immaculatum. Stamina 6, filamentis
perbrevibus; antberis bifldo-didymis. Spicae femineae solitariae 1-4 florae;
capsulis circumscriptione obcordatis 2 cm. longis, aetate castaneis. Semina
fusca.— //. W. Ravenel, " Santee Canal, South Carolina " { $ ) ; II. H. Bartlett,
1468, " Branch swamp," McDufhe County, Georgia, September IS. 1908 ( 2 ).

<i Dioscorea floridana sp. nov. Rhizoma ignotum. Caulis scandens, flexuosus,
glaber. Folia cordata, alterna, utrinque glabra, supra viridia, subtus pallidiora,
7-uervia, nervis exterioribus biiurcatis. Inflorescentiae masculae paniculi-
formes et caulem terminantes et binis trinisve in folioi-um axillis superiorum
fasciculatae; floribus aut singulis aut binis sessilibus, valde flavis, maculatis;
staminibus hand didymis. Spicae femineae pendulae, solitariae, ca. 6-florae.
Capsulae foi-ma eis D. paniculatae similes, ca. 2 em. longae. — " Moist thickets,
Lake City, Fla.," P. H. Kolfs, 266 {$), June 18, 1894; Charleston, S. C, in
Herb. Bost. Soc. Nat. Hist. ( $ ) .
189

THE DEUG DIOSCOREA. 19

of the stem, however, the transition from leaves to subulate bracts is
not gradual but sharp.
Specimens examined :

Sorth Carolina. — CMiieston County (specimen in Herb. Bost. Soc. Nat. Hist.).

Georgia. — Jefferson County, M. II. Hopkins, 91 ; Sumter County, R. M. Harper,
13S9.

Florida. — Columbia County, P. H. Rolfs, 266; Escambia County, A. H. Curtiss,
in 1885.

THE DRUG DIOSCOREA.

According to Mr, C. G. Lloyd the rhizome of Dioscorea was first
brought to the attention of " botanic physicians " by Dr. J. L. Rid-
dell " in 1835, although before that time it had been used more or less
as a " secret remedy." ^ Riddell's account of the plant, which was
copied in part by most subsequent writers, was as follows :

1501. Dioscorea villosa, Linn. Yam root. China root. May-June. Yellow-
wliite. Climbing vine, G to 12 f. Koot woody, tortuous, echinate. Open woods.
Bottom lauds. Western States. An infusion of the powdered root is to be boiled
in a pint of water, and half of it given at once. * * * I have been informed
that Doctor Miller, of Neville, Ohio, values the tincture highly as an expectorant.
He says it is also diaphoretic, and, in large doses, emetic."

In 1836, a year later, William Hance'' published a much fuller
account of Dioscorea, which, on account of the evidence it affords
regarding the identity of the species used at that time, is here quoted
in full:

Dioscorea villosa. Common names — Yam root, China root. — This plant is a
twining and climbing vine, resembling in some respects the morning glory. The
i-oot is of a most singular tortuous form, of a woody consistence, with numerous
spiny protuberances. It is perennial, and doubtless endures a greater number of
years than the roots of most plants of similar habits. The sprangles are usually
near half an inch in thickness, and the whole root in favorable situations is
often found to weigh half a pound. The stem is a climbing annual vine, winding
around small shrubs, and insinuating itself among brambles, often attaining
the height of 6 or 8 feet. Near the ground the leaves usually appear in ver-
ticillate clusters, or whorls, varying in number from two to eight or more in a
bunch, dependent on the luxuriance of the soil. Higher up the leaves are alter-
nate. They are always on pretty long footstalks and of the form of a heart, with
the point acute and turned to one side ; commonly roundish as well as cordate
and nearly 2 inches across. Almost always you may count just nine nerves
or portions of framework, proceeding from the base toward the apex. The
flowers show themselves in May and June; they are very small and white,
arranged on little stems which come out just above the leaves. The seeds are
triangular, some like buckwheat, though four times as large, with wings at the
angles. The yam root grows plentifully in the Western States, delighting in
fertile hillsides, thickets, and open woods.

a A Synopsis of the Flora of the Western States (1835).

^ See Transactions, N. Y. State Eclectic Medical Society, for 1870. D. E. Smith,
" Dioscorea."

c Howard's Botanic Medicine, ed. 3 (1836), ii, p. 240.
189

20 THE SOUECE OF THE DEUG DIOSCOREA.

An infusion of the root is a valuable remedy in bilious colic. An ounce of the
powdered root must be boiled in a pint of water, and half of it given at a
dose. * * * I iiave been informed that Doctor INIiller, of Neville, Ohio, values
the tincture highly as an expectorant. He says it is also diaphoretic, and in
large doses emetic.

For the introduction of the dioscorea into this work we are indebted to the
kindness of our friend, Dr. J. L. Riddell. He has not informed us upon what
principle it is supposed to afford relief in bilious colic, whether as an anodyne,
cathartic, or some other. We have no doubt, however, of its value in this com-
plaint, and, at the same time, think it highly probable that further investigation
will disclose its usefulness in other diseases.

It will be observed that the plant described by both Kiddell and
Hance was Dioscorea glauca Muhl. The description of the rhizome as
" singularly tortuous, with numerous spiny protuberances " and
" sprangles usually near half an inch in thickness," and of the leaves
as " verticillate, from two to eight in a bunch," leaves no. doubt con-
cerning the plant which they used. In this connection it should be
observed (see fig. 2) that D. glauca occurs in southern Ohio, where
Riddell might have observed it. By the time King« published his
Dispensatory, however, one of the species with slender rhizomes had
come into use in eclectic medical practice. King's description in-
cluded characters of two or three species and was obviously compiled
from earlier authors. The rhizome, however, he undoubtedly de-
scribed from his own knowledge of it as " long, woody, contorted, from
an eighth to a fourth of an inch in diameter." He doubtless used D.
panicidata. This species was also used by W. S. Merrell in the prepa-
ration of his " dioscorein," and at that time (about 1850) was the
only plant recognized by the eclectic school as " Dioscorea viUosa^
It must be remembered, however, that the "Z>. villosa " of " Howard's
Botanic Medicine " was D. glauca. The history of dioscorea be-
tween 1850 and 1880 can not be better outlined than by quoting from
Mr, C. G. Lloyd's article in the Supplement to the eighth edition of
King's Dispensatory.'' In order to make the quotations intelligible the
" Plate VII," which is referred to, is here reproduced as figure 4 :

The rhizoma of Dioscorea villosa is a favorite tlierapeutical agent among
our eclectic physicians, who have advantageously used it for more than
forty years. It is known as wild yam and colic root. The first specimens
employed were from the Dioscorea villosa, with pubescent leaves (fig. 2,
PI. VII), now known as the "true wild yam." About tlie year 1850 botanic
druggists noticed the admixture by root diggers of the rhizomata represented
by figure 1, Plnte VII. and for a considerable time rejected it as an adulteration.
The diggers insisted, however, that both "roots" were obtained from vines
almost identical in appearance (although they can distinguish between them),
and finally purchasers were compelled to accept them, more especially as the

^American Eclectic Dispensatory (1854), p. 440.

& Supplement to the American Dispensatory, by John King and John Uri
Lloyd (1880), pp. 81-83.
189

THE DRUG DIOSCOREA.

21

true rliizomata became very scarce. Mr. H. M. Merrell, of Cincinnati, Ohio,
to whom we are indebted for this information, states that the first heavy ship-
ments of the false " wild yam root " to eas^tern houses were made about 1860,
whh?h article purchasers refused to accept, but after some correspondence,
■coupled with the fact that the true wild yam could not at that time be obtained,
the parties concluded to receive it. Since then the two rhizomata have been
sold indiscriminately, although but little of the original drug is to be found in
the market. Eclectic physicians are aware of the difference between these
rhizomata and refuse to use the "false" variety, insisting that it does not
possess the medicinal properties, and can not safely be substituted for the
" true." In this connec-
tion we invite attention
to the accurate engrav-
ings of each variety of
the rhizomata in Plate
VII. [See fig. 4.]

The rhizoma of Dios-
corca rillosa (PI. VII,
fig. 2) appears in market
in s 1 e n d e r contorted
pieces from one-fourth of
an inch to half an inch
in diameter, and often 2
feet in length. It is oval,
being flattened above and
below as it creeps in a
horizontal position be-
neath the surface of the
ground. It seldom throws
out branches, but occa-
sionally little protuber-
ances project from its
sides, being from one-
eighth of an inch to an
inch in length and about
one-third as large in
diameter as the primary
rhizoma. They are round-
ing at the extremity,
and seem to indicate an
abortive attempt of the
rhizoma to throw out
branches, but they do
not send up the vine. Along the upper side of the rhizoma are stem scars, which
are about three-fourths of an inch apart. The epidermis is brown, thin, and
scales off, more or less, upon drying, especially when the rhizoma is gathered in
the spring, but which is not the case with a good quality of it when dug in
autumn. The internal color of the dry rhizoma is whitish, or slightly straw
colored, when gathered in the autumn, but it is often brown when collected early
in the season ; there is no bark to it. Under a magnifying glass the texture of a
broken rhizoma apjiears mealy and perforated with numerous woody bundles.
Attached to the lower part of the rhizoma an abundance of strong, wirelike fibers
will be observed. * * * Dioscorea villosa has one of the firmest of rhizo-

189

Fig. 4. — Reproduction of Plate 7, " Dioscorea rillosa," from
King and Lloyd's " Siipplempnt to the American Dis-
pensatory." (Reduced one-third.)

22

THE SOURCE OF THE DRUG DIOSCOEEA.

mata, it being very difficult to powder or crush. It has no odor and but liUIe
taste beyond a slight acridity after prolonged chewing. The virtues appear to
reside in an acrid resin, almost insoluble in water, but readily extracted by
alcohol. The so-called dioscorein is not a definite principle of the rhizoma, but
is simply a dried solid extract, and to call it otherwise is a misnomer.

Dioscorea villosa var. gJahra. — This appears to us to be a distinct variety,
chiefly differing from the preceding in the entire dissimilarity of its rhizomata.

This plant closely resem-
bles the true wild yam
in its general shape, and
in the structure of its
leaves, flowers, and fruit.
The leaves, however, are
entirely glabrous and are
not covered with a short
pubescence underneath.
This distinction we have
invariably found in every
instance where we have
examined the growing
plants, hence the under-
surface of the leaf will
readily determine the
character of the rhizoma.
The two plants likewise
appear to differ in their
manner of growth, the
D. villosa often growing
in dense clumps while
the variety ylahra is gen-
erally found isolated.

The rhizoma (PI. VII,
fig. 1) of I>, villosa var.
glabra i-esembles that of
Colliiisonia Canadensis
more nearly than it does
the true D. villosa. It is
found as a rough clump
of a pound or more in
weight when fresh,
thickly branched, each
branch shooting from the
side of the main rhizoma
at an angle inclining
backward and upward.
The branches almost
touch each other, are as
large as the rhizoma, and
are from 1 inch to 3 inches in length. Along their upper surface are numerous
cup-shaped stem scars, which are about one-fourth of an inch or one-third of an
inch in diameter and so thickly inserted as to intrude upon each other. The
vine of the true D. villosa, upon the contrary, springs fi'om the main rhizoma.
The diameter of the rhizoma and of the ramifications is from half an inch to
three-fourths of an inch, and the length seldom mox'e than 6 inches. Internally
189

Fig. 5. — Rhizome of Dioscorea glaucu. Mountain form
from the summit of House and Barn Mountain in Russell
County, Virginia, collected by C. L. Alsberg. (Three-
fourths natural size.)

THE DEUG DIOSCOKEA.

23

the rhizoma resembles that of the true wild yam, while the lower portion is in
like manner covered with stout fibrous rootlets. The color is generally a very
much darker brown.

It will be observed that Mr. Lloyd's " true " Avild yam is Dioscorea
paniculata and that his " false " variety is D. glcvuca^ the species
first authoritatively introduced into eclectic practice. With regard to
his criterion for distinguishing "Z>. villosa " from "Z>. villosa var.

Fig. 6. — Rhizomes of Dioscorea paniculata from Agricultural College, Ingham Co., Mich.,
collected by W. .1. Deal. (Two-thirds natural size.)

glahra " (the pubescence of the lower leaf face), it must be said that
D. glauca^ the plant Avith the large, coarse rhizome, although some-
times glabrous, is oftener somewhat pubescent on the leaves beneath,
and that D. paniculata^ the species with slender rhizomes, has
a variety with the leaves entirely glabrous. To make this point
clear, the attention of the reader is directed to figure 5, which illus-
trates the rhizome of a specimen of D. glauca with the leaves slightly

189

24

THE SOURCE OF THE DRUG DIOSCOREA.

pubescent beneath, and figures 6 and 7, illustrating rhizomes of
D. paniculata and its variety glahrifolia.

"When Dioscorea glmica grows at Ioay altitudes its rhizome is less
branched and contorted than Avhen it grows in the mountains. In
the Aicinity of Washington. D. C, its rhizome is often as unbranched
as the rhizome of D. quatemata^ and might be mistaken for that

Fig. 7. — Rhizomes of Dioscorea paniculata var. ijlubrifulia from Gloundale, Prince Georges
Co., MfL, collected by H. H. Bartlett. (Two-thirds natural size.)

species, but its greater diameter still suffices to distinguish it from
D. paniculata. The form of rhizome which occurs most frequently
in the drug trade at the present time is well illustrated by figure 8.
This particular specimen was obtained through the kindness of
Mr. R. W. Proctor, of Cincinnati. Ohio. As a general rule, collectors
of Dioscorea who supply the drug market do not distinguish between

189

THE DEUG DIOSCOREA.

25

the different kinds. The same common names are used for all of the
species. Wild j^am is the name used over the largest area. The
following names have also been reported by correspondents of the

y-

FiG. 8.- — Kbizome of Dioscorea glauca. Typical drug from South Portsmouth, Greenup
Co., Ky., collected by John Butler. (Two-thirds natural size.)

Department of Agriculture: Colicroot, chinaroot, devil's-bones
(North Carolina) ; hobs-grub (Tennessee) ; rattlebox, cramproot
(Kentucky).

180

INDEX.

Page.

'Anonymos (Dioscoreae affinis?) quaternatus, " etc., reference 10

quinatus," etc.. reference 10

■'Bryoniae nigrae gimilis floridana," publication 7

Burman, editions of Rumpliius and Plumier 9

statement regarding '"Index Universalis" of ''Herl^arium Amboi-

nense " 10

Chinaroot, common name for Dioscorea 25

Clayton, collector of Dioscorea specimen in Gronovian herbarium 8

Colicroot, common name for Dioscorea 25

Cramproot, common name for Dioscorea 25

Devil 's-bones, common name for Dioscorea - - 25

. Dioscorea, common names 25

description by Riddell 19

floridana, description 18-19

distribution 18-19

specimens examined 18

glauca, a nomen sul>nudum 10-11

description 13

distribution 13-14

forms of rhizome 24

identity with D. villosa of Riddell and Hance 20

var. glabra of Lloyd 23-24

synonymy 11

hexaphylla, reference to D. glauca 11

hirticauliS: description 17-18

distribution 18

specimens examined IS

longifolia, reference 11

megaptera, reference to D. glauca 11

paniculata, abnormal pistillate inflorescence 16

description 15

distribution 15, 16-17

form of rhizome 23-24

identity with D. villosa of Lloyd 23-24

occurrence in Massachusetts, report 16

original publication 8

source of ' ' dioscorein " 20

var. glabrifolia, description 15

distribution 15, 17

form of rhizome 24

pruinosa, reference to D . glauca 11

189 27

28 THE SOURCE OF THE DRUG DIOSCOREA.

Page.

Dioscorea quatemata, acceptance by Pursh, Nuttall, Elliott, Beck, and Kunth. 10

description 12

distribution 12-13

form of rhizome 24

publication by Gmelin 10

synonymy 11

quinata, publication by Gmelin 10

repanda, reference to D. glauca and D. quaternata 11

sativa, identity of Linnsean specimen with D. paniculata 8

Linnsean diagnosis 9

synopsis of species occurring in United States 11-19

the drug, medical history 19-25

United States, taxonomic history 7-11

villosa, description by Hance 19-20

identity of drug described by King 20

Lloyd as "true" wild yam. . . 23-24

Riddell and Hance 20

inapplicability of name 9

Lloyd's description 21-22

opposite-leaved elements 9, 10

origin of specific name '. . 8

original publication 7

use as secret medicine, history by D. E. Smith 19

var. glabra, Lloyd's description 22-23

publication 11

reference to D . glauca 11, 23

Dioscorein, preparation by W. S . Merrell 20

Gmelin, publication of Dioscorea quaternata and D. quinata 10

"Gray's Manual, " seventh edition, treatment of Dioscorea 11

Hance, William, account of Dioscorea in Howard's "Botanic Medicine" 19-20

identity of drug described 19-20

Hobs-grub, common name for Dioscorea 25

Jackson, B. Daydon, Linnaean specimens, letter 7-8

Kalm, collector of Dioscorea specimen in Linnsean herbarium 8

King, John, identity of drug described 20

Kunth, publication of Dioscorea pruinosa 11

Lamarck, origin of Linnsean diagnosis of Dioscorea villosa 9

Linnseus, specimen of Dioscorea in herbarium 7

treatment of Dioscorea in ' ' Species Plantarum " 7,9

Lloyd, C. G., history of drug Dioscorea 19, 20-23

publication of Dioscorea villosa, var. glabra 11 , 22

Merrell, W. S., dioscorein, preparation 20

Muhlenberg, herbarium 11

publication of Dioscorea glauca 10-11

treatment of Dioscorea 11

Nomenclature, botanical, Vienna code, provision for rejection of certain names. . 9

" Polygonatum scandens altissimum," an element of Dioscorea villosa 9, 10

Rafinesque, description of Dioscorese 11

Rattlebox, common name for Dioscorea 25

Rendle, specimen of Dioscorea in Gronovian herbarium, description 8

Richard, description of Dioscorea paniculata 8-9

Riddell, J. L., description of Dioscorea 19

Rumphius, reference of Ubium nummularium to Dioscorea villosa 9, 10

189

INDEX. 29

Page.

Smith, D. E., history of use of Dioscorea as secret medicine 19

Stickman, Linntean references in "Herbarium Amboinense" 10

Ubium nummularium, an element of Discorea villosa 9, 10

United States, Dioscorea, synopsis of species 11-19

taxonomic history 7-11

Vienna code. See Nomenclature, botanical, Vienna code.

Walter, " Anonymos (Dioscoreae affinis?) quaternatus, " reference 10

quinatus, " reference 10

Wild yam. See Yam, wild.

Yam, wild, false, root 21, 23

most common name for Dioscorea 25

true, description 20, 23, 25

189

o

[Continued from page 2 of cover. ]

No. 102. Miscellaneous Tapers. 1907. Price, 1.5 cents.

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188. Dry Farming in Relation to Rainfall and Evaporation. [In press.] J

189 :

U. S. DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 190. ^

B. T. GALLOWAY, Chief of Bnreav.

ORCHARD GREEN-MANURE CR0P8

IN CALIFORNIA.

BY

ROLAND MgKEE,

SriENTTFTO ASSLSTANT, OfFKE OF FoRAGE-CrOP

Investigations .

IwiKI) OcTOBEIi L'7. UUO.

.WASHINGTON:

GOVERNMENT PRINTING OFFICE.
1910.

BULLETINS OF THE BUREAU OF PLANT INDUSTRY. ^

'I'lu; scientific and tt'chnical {(ublications vi Ihc Bureau of Plant Industry, which was orsjanizcd July 1, ' .!

I!t0l, are issued in a single series of bulletins, a list of which follows. - '•

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i;»0 ' [Contimied oupageaofcovcr.] -]

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 190.

B. T. GALLOWAY, Chief of Bureau.

ORCHARD GREEN-MANURE CROPS

m CALIFORNIA.

BY

KOLAND McKEE,

Scientific Assistant, Office of Forage-Crop
Investigations.

Issued October 27, 1910.

LIBRARY
NEW YORI
BOTANICA

QARDBN.

WASHINGTON:

government printing office.

1910.

BUREAU OF PLANT INDUSTRY.

Chief of Bureau, Beverly T. Galloway.
Assistant Chief of Bureau, G. Harold Powell.
Editor, J. E. Rockwell.
Chief Clerk, James E. Jones.

Foeage-Ceop Investigations.

scientific staff.

C. V. Piper, Agrostologist in Charge.
J. M. Westgate, Agronomist.

R. A. Oakley and H. N. Vinall. Assistant Agrostologists.
S. M. Tracy, Special Agent.
A. B. Conner, A. B. Cron, M. W. Evans, Roland McKee, and W. J. Morse, Assistants.

190

2

LETTER OE TRANSMITTAL.

U. S. Department of Agriculture,

Bureau of Plant Industry,

Office of the Chief,

Washington, D. C, July 2, 1910.
Sir : I have the honor to transmit and to recommend for pubHcation
the accompanying manuscript, entitled "Orchard Green-Manure Crops
in Cahfornia," by Mr. Roland McKee, Scientific Assistant in the
Office of Forage-Crop Investigations, and recommend its publication
as Bulletin No. 190 of the Bureau series.

Leguminous cover crops are now extensively used in California
citrus orchards, but only to a slight extent in deciduous orchards.
Owing to peculiar conditions certain legumes are especially adapted
for use in that State, while their usefulness elsewhere is limited.

The results presented in this bulletin are based on the investiga-
tions that have been conducted at Chico, Cal., and in cooperation
with many orchardists for the past five years.
Respectfully,

G. H. Powell,
Acting Chief of Bureau.

Hon. James Wilson,

Secretary of Agriculture.

190 Q

CONTENTS

Page.

Introduction 7

The orchard districts of California 8

Southern citrus section 8

Northern citrus section 9

Deciduous orchard sections ' 9

Conditions under which green-manure crops should not be used 10

Qualities desirable in a green-manure crop 10

Methods of handling green-manure crops 11

Preparation of the land 11

Seeding 12

Irrigation 12

Turning under a green-manure crop 12

Inoculation 14

Commercial fertilizers 15

Winter green-manure crops now used in California orchards 15

Common vetch 15

Canada field peas 17

Bur clover 19

Fenugreek 20

Adaptation 21

Comparative value 21

Planting 22

Seed production 23

Hairy vetch 23

Indian melilot 24

Summer green-manure crops 24

Results of green manuring in California 25

Results of tests with various legumes 25

Promising green-manure crops 27

Black-purple vetch 28

Black bitter vetch 29

Woolly-podded vetch 30

Horse bean 30

Tangier pea 32

Cost of seed of green-manure crops 32

Summary 34

Index 37

190 5

ILLUSTRATIONS.

Page.
Fig. 1. ViewinaCaliforniaorangegrove, showing the method employed in plow-
ing under a green-manure crop 13

2. Experimental plats of horse beans at Chico, Cal., showing the striking

superiority of the noduled plants 14

3. View in an orange orchard in southern California, showing common

vetch grown as a green-manure crop 16

4. View in an orange orchard in southern California, showing Canada field

peas grown as a green-manure crop ,. - - 18

5. An individual plant of fenugreek, showing its characteristics 20

6. View in a walnut orchard in Orange County, California, showing fenu-

greek grown as a green-manure crop 21

7. A field of black-purple vetch at Chico, Cal 28

8. A field of black bitter vetch at Chico, Cal 29

9. View in a citrus orchard in southern California, showing horse beans

grown as a green-manure crop 31

190
6

B. p. I.— 592,

ORCHARD GREEN-MANURE CROPS IN CALIFORNIA.

INTRODUCTION.

The use of green-manure crops for the maintenance of soil fertihty
is one of the oldest of agricultural practices. In California such
crops have been used in a limited way for a long time, yet it is only
within recent years that their practical value has become fully recog-
nized. The growing of these crops has attained its greatest develop-
ment in the citrus orchards of the southern part of the State, where
they have been longest used.

As far back as the early nineties some of the more progressive
orchardists were beginning to realize the necessity of some such prac-
tice as green manuring and to this end utilized the natural growth
of bur clover and other weeds, such as alfilaria,'* brome-gr asses, etc.
The Canada field pea was the first of the legumes to be used exten-
sively as a green-manure crop, and by 1900 it was bemg quite gen-
erally grown in the citrus orchards of the southern part of the State.
Common vetch and bur clover were also being utilized at this time.

In many parts of California, green-manure crops have not been used
to any extent, but not entirely without reason. That their use can
be made much more general than at present is quite certain, and as
their value is more fully appreciated and their adaptation to the
various sections demonstrated their use will be proportionately
increased.

For a number of years the Bureau of Plant Industry has been work-
ing to secure better crops for green manuring than the ones now used
and to aid in the demonstration of the adaptability of the ones now
being grown. The Agricultural Experiment Station of the Uni-
versity of California has also done extensive work in demonstratmg
the value of various green-manure crops in that State.

In California the work of the Bureau of Plant Industry has been
carried on in cooperation with orchardists and farmers throughout
the various sections and at the United States Plant Introduction
Garden at Chico, where extensive tests have been made. This work
has clearly indicated the superiority of certain crops over others and
their adaptation for varying purposes and conditions.

a Known also as alfilerilla and pin-grass.
190 7

I

8 OKCHAKD GEEEN-MANUEE CEOPS IN CALIFOENIA.

THE ORCHARD DISTRICTS OF CALIFORNIA.

The orchard districts of Cahfornia so far as green-manure crops
are concerned at once divide themselves into the citrus and the
deciduous fruit districts. These are again readily divided into the
northern and southern citrus districts and the irrigated and nonirri-
gated deciduous sections.

The two citrus districts have a definite geographical distinction,
while with the deciduous orchards water is the differentiating factor,
without reference to any geographical distinction. The citrus dis-
tricts are quite definite in area. The southern district is confined to
what is known as southern California proper and includes the territory
south of the Sierra Madre Mountains and north along the coast to
Santa Barbara. The northern district includes a narrow strip on the
east side of the San Joaquin VaUey from some distance south of
Porterville to Lemoncove, Tulare County, on the north; a similar
but smaller area in Fresno County; a small area in the Sacramento
Valley, centering about Oroville and Palermo; and various small
areas in other parts of the valleys and foothills.

Conditions with regard to water, soil, climatic or seasonal varia-
tions, etc., are quite different in these various sections, and the plant
best suited to a certain area must be carefully considered in deter-
mining the probability of success with a green-manure crop. Prac-
tices satisfactory in one locality may be unsuited to another, and the
crop best adapted to one section may not be adapted to another.

SOUTHERN CITRUS SECTION.

The seasonal conditions of the southern citrus section are such as
to maiie this the most favorable part of the State for growing green-
manure crops. The locahty and climatic conditions are such that
these crops are practically never injured by frosts, and the mild
winters favor vegetative growth at that time of the year.

In contrast with the deciduous sections, where there is usually a
heavy rainfall, here the rainfall is usually light. However, as irriga-
tion is given throughout the dry season the conditions are favorable
to the sowing of a green-manure crop early in the fall, thus giving
sufficient time for considerable growth before the cold weather of
winter.

The soils vary considerably in composition and mechanical texture,
but as a general rule are of such a nature as to permit working at
almost any time during the winter, except after heavy rains, thus
favoring the turning under of a green-manure crop. While some
soils in this section are a rich loam and contain considerable organic
matter, as a rule they are quite deficient in this respect. That green
manures need to be more extensively used is evident.

190

THE ORCHARD DISTRICTS OF CALIFORNIA. 9

NORTHERN CITRUS SECTION.

The northern citrus section, as previously stated, comprises a small
region in the San Joaquin Valley, centering about Porterville and
Exeter, and a smaller section in the Sacramento Valley, centering
about Oroville and Palermo, besides small areas in various parts of
the valleys and foothills of the State. The conditions in this district
differ very much from the conditions in the southern California dis-
trict, and in these differences is found the reason why green-manure
crops have been but little used.

The seasonal conditions at the north wliile favorable to the growth
of green-manure crops are less favorable for their handling. The
rainy season is quite definite, extending through January and Feb-
ruary, and sometimes into March. The soil, which is heavy, dries out
slowly during the winter season, often making it impossible to get
into the orchard to turn under a crop at the proper time. Thus, when
the season for turning under is delayed, a heavy vegetative growth is
objectionable in that it makes the land hard to work and at the same
time by shading prevents it from drying out to allow of cultivation
as early as otherwise would be the case. The soils throughout the
northern district are with few exceptions of the very heavy nature
referred to, and for this reason a heavy vegetative growth is often a
hindrance to proper handling. While the immediate effects of a
green-manure crop may be undesirable, there is but httle question
that these lands need to be made lighter by the addition of humus,
and results that appear at the time as unfavorable can well be toler-
ated when the ultimate effect will be an improved condition.

Green manures have been used but little in the northern citrus
section. However, the results from a few plantings, together with
the experimental work done, clearly show that by early seeding a
good green-manure crop can be grown and in most cases can be
profitably used.

DECIDUOUS ORCHARD SECTIONS.

While the deciduous orchards are scattered throughout the State
of California they are largely in the northern part and are mostly
located on the fertile lands of the various river valleys and the low
foothills. Green-manure crops have not been used to any extent in
these orchards, and practically the only thing approaching such a crop
is the volunteer growth of bur clover, which is usually sufficient by
the time the orchards are plowed in the spring to yield considerable
humus.

The problem of growing a green-manure crop in deciduous orchards
is quite different from that of growing the same crop ih citrus
orchards. This difference lies principally in the fact that the former
52810°— Bull. 190—10 2

10 OECHAKD GEEEN-MANUEE CEOPS IN CALIFOENIA.

are not irrigated, or if water is applied it is early in the summer, and
not in the fall when it could be utiUzed in starting the crop.

Winter rains must be depended upon to germinate seed sown in the
fall, and only in the most favorable seasons are they early enough to
allow much growth before cold weather. When the first rains come
late, but little growth is made by fall-sown seed until the warmer
weather of the latter part of winter or early spring. Thus, only in
the most favorable years will the growth be sufficiently early to
allow its utilization for green manure. Where water is available for
fall irrigation the question ceases to be one of the possibility of grow-
ing a good green-manure crop and becomes one of the returns justify-
ing the expense.

CONDITIONS UNDER WHICH GREEN-MANURE CROPS SHOULD NOT

BE USED.

There are some sections in which green-manure crops can be grown
satisfactorily, but their utility nevertheless seems questionable. This
is especially true in lemon orchards having a very heavy soil, and to
a less degree in orange orchards. By a heavy soil is not meant a
heavy loam, but an adobe or a soil approaching that texture. On
such soils the discontinuance of cultivation which is necessitated by
the growing of a green-manure crop allows the soil to become quite
hard and packed, thus permitting very imperfect aeration. This is
a most undesirable soil condition to maintain during a period of sev-
eral months, and its injurious effects may be seen in the unthrifty
appearance of the trees. Where this effect is very marked it is
undoubtedly best not to use a green manure, but to use stable manure
instead, if such is available.

In the Porterville and Oroville citrus districts, where the soils are
quite generally of a heavy type, the foregoing statement does not
apply as definitely as in the southern California districts. This is
due to seasonal differences. The trees in the two former sections
have a more nearly dormant period of growth during the early win-
ter than those in the latter, in which case the effect of noncultivation
is not so marked. Wliere on account of heavy soils it is not advisable
to grow a green-manure crop, stable manure, if available' should be
used in lightening the soil.

QUALITIES DESIRABLE IN A GREEN-MANURE CROP.

No one plant possesses all the desirable qualities of an ideal green-
manure crop. However, in the various crops used for such pur-
poses, practically all the desirable qualities are represented, though
varying in degree. The conditions under which a green manure is to
be grown determine to some extent whether a certain quality is

190

METHODS OP HANDLING GREEN-MANUEE CROPS. 11

desirable or objectionable and must be taken into consideration in
selecting the best crop to grow.

A green-manure crop should be a legume wherever possible, in
order to obtain the addition of nitrogen to the soil. It is also neces-
sary that a good growth be made, in order to have a large quantity of
organic matter to turn under and incorporate with the soil. Along
with good growth should be a heavy development of nodules on the
roots, as this is believed to indicate great ability to fix atmospheric
nitrogen.

The quality of being able to stand trampling with a minimum of
injury is very important where the crop will be subject to such injury,
as is the case in citrus orchards where the picking of fruit takes
place while the green-manure crop is yet growing. Uprightness and
nontwining stems are also desirable where an ordinary moldboard
plow is depended upon for turning under the crop. However, if a
disk plow is used or the crop is worked in with an ordinary disk
harrow, this does not make so much difference, and where the growth
is not allowed to become too rank little difficulty is experienced in
plowing it under.

The texture of the stem should be such as to decompose readily.
Practically all crops, however, if turned under at the right stage of
growth decay readily. Thus, the question of decomposition is one of
turning under the crop at the right time rather than one of selecting
a crop that will decay readily.

That the cost of a green manure may not be too great, it is neces-
sary that the price of seed be reasonable as compared with the results
to be obtained.

METHODS OF HANDLING GREEN-MANURE CROPS.

The methods of handling green-manure crops in California are
quite similar throughout the various sections. However, some vari-
ation in practice exists among orchardists in the same neighborhood, as
well as among those of different localities.

The following methods are practiced in the citrus and walnut
orchards of the southern part of the State, where green manures have
been most generally grown.

PREPARATION OF THE LAND.

Since clean culture is practiced throughout the year in citrus and
walnut orchards except when a green-manure crop is being grown,
the land can be prepared at any time for the seeding of such a crop.

The general practice is to prepare the land for seeding by plowing
or disking and harrowing immediately after an irrigation. This puts
the land in good condition for the seeding.

190

12 OKCHAED GEEEN-MANUEE CEOPS IN CALIFOENIA.

SEEDING.

The most successful growers of green-manure crops sow vetch and
bur clover in the first half of September, and peas during the latter
half of the same month. Early seeding is being much more generally-
practiced now than it was a few years ago, when the greater part of
the crop was sown in October. The time of irrigation of an orchard
determines to some extent when a green-manure crop shall be sowti,
as water is not always available at the time desired. However,
when water is available the time mentioned is that most generally
favored for irrigation.

The seed is sown either drilled or broadcast and harrowed in.

IRRIGATION.

After the seed is sown and before it germinates, the land is prepared
for fall or winter irrigation if necessary. The furrow method is the
one most commonly used. This consists in making a number of
shallow furrows between the rows in the direction the water is to
flow, the method varying in different sections and with the lay of the
land.

The basin method is used to quite an extent in the walnut orchards
of the southern part of the State and in the orchards of the Santa
Clara Valley."

Nothing further is done, with the exception of irrigating if neces-
sary, until the crop is ready to turn under. Wlien a crop is so^\ti in
September it can be plowed under during February.

TURNING UNDER A GREEN-MANURE CROP.

In turning under a green-manure crop the common moldboard
plow (see fig. 1), the disk plow, or the disk harrow is used. In using
the first a sharp colter is attached, and where the vine growth is
heavy a chain is also used. Sometimes the land is run over once
with a disk harrow before plowing. This enables a heavy growth to
be more completely turned under. During the past few years the
disk plow has been very generally used, and for turning under a heavy
vine growth it works more satisfactorily than the moldboard plow.

After plowing under a green-manure crop the land is harrowed,
and as the crop decays cultivation is given. This at first is shallow,
so as not to bring the vines to the surface, but later a deeper cultiva-
tion is given.

In sections having a very open soil or a sandy loam the disk harrow
has been used very successfully iti turning under a green-manure
crop. The use of this harrow has been taken up with the idea that
fewer surface-feeding roots of the trees are disturbed by its use than

a See Bulletin 145, Office of Experiment Stations, pp. 46-50.
190

METHODS OF HANDLING GREEN-MANURE CROPS.

13

is the case with the plow, for which reason it is thought by many to
be more desirable. In working a green-manure crop into the soil
wdth a disk harrow, four diskings are usually required, each disking,
where the planting of the orchard will permit, being made at an angle
with the previous one. On the heavier soils the disk harrow does not
work so well and the plow is used almost entirely.

After turning under a green manure the land is kept well cultivated
the remainder of the year.

For obtaining the best results a green-manure crop should be
turned under early enough in the season to allow perfect decomposi-

* V

9'<^-^~.

>-^

^ . X ,^ff^^-

Fig. 1.— view in a California orange grove, showing the method employed In plowing under a green-
manure crop.

tion. In orchards this can be quite definitely designated, as the
turning under should take place before the trees start growth in the
spring. This means, for citrus orchards in southern California, not
later than February. In northern California the season is of neces-
sity a little later on account of the generally wet condition of the soil
at that time. Where the factors relating to other crops and a season
favorable to decomposition do not have to be taken into considera-
tion, it perhaps is safe to say that to obtain the best results most
legumes should be turned under about the time the first pods form,
or a little earher.

190

14

ORCHARD GREEN-MANURE CROPS IN CALIFORNIA.

INOCULATION.

The question is often asked whether it is not advisable to inoculate
seed to be sown on land that has not previously growTi that crop. In
California it has been found that the bacteria necessary to nodule
formation on the more common leguminous crops are present in most
soils. The first seeding may not, however, be as abundantly inocu-
lated as desired, and in some sections the bacteria essential to certain
crops seem to be entirely lacking in the soil.

In northern California it has been observed that horse beans are
not inoculated the first year they are grown on soil that has not pre-

^ .--- --«rs;*^.

rj '}>-

'^ ^i

■'1. ■:« ';

Fig. 2.— Experimental plats of horse beans at Chlco, Cal., showing the striking superiority of the noduled

plants.

viously grown this crop. (See fig. 2.) Thus, to obtain the best
results, it is necessary to inoculate the crop the first year. The dif-
ference between an inoculated and an uninoculated crop of horse
beans in the Sacramento Valley is very marked and is practically
the difference between success and failure. In southern California
this crop does not require artificial inoculation, the soil being inocu-
lated.

In the inoculation of horse beans the surest results are obtained by
securing soil from an inoculated plat or field and mixing this with
the seed at the time of seeding. In this way but little soil will be
required to inoculate a large area, and practically no extra time or

190

WINTER GEEEN-MANUEE CEOPS. 15

labor is necessary. The inoculation of this crop may also be attained
by spreading inoculated soil over the field at the time of seeding and
working it in Avith the seed, or the seed may be inoculated with pure
cultures of the bacteria which form nodules on the roots of this plant.
Such cultures have been distributed by this Department for several
years, and the results obtained from their use have been favorable in
many cases.

COMMERCIAL FERTILIZERS.

In the citrus orchards of California commercial fertilizers are quite
generally applied, while in few deciduous orchards are fertilizers used
in any form. "\A'liere fertilizers are used they are usually applied in
connection with a green-manure crop.

The value of a green-manure crop is largely due to the part it plays
in liberating plant food in the soil. In the deca}^ of organic matter
and the giving off of carbonic-acid gas, the action on phosphorus and
potassium compounds is such as to make them more available as
plant food. Vegetable acids, which are always more or less present
with a green-manure crop, also aid in liberating plant food. Thus,
elements present in a soil but not available as plant food may be
made so by the use of a green manure.'*

From the facts just stated it will be readily seen that a green-
manure crop may serve a useful purpose when used in connection
with commercial fertilizers, especially where the various plant-food
elements are only partially available in the soil.

WINTER GREEN-MANURE CROPS NOW USED IN CALIFORNIA

ORCHARDS.

The green-manure crops now used in California, in the order of
their importance, are as follows: Common vetch, Canada field peas,
bur clover, fenugreek, hairy vetch, and Indian melilot.

Common vetch and field peas are by far the most extensively
planted, while hairy vetch and melilot are very little used. Bur
clover and fenugreek are used to but a limited extent, although they
are of considerable importance.

COMMON VETCH.

The common or spring vetch (Vicia sativa) is the most exten-
sively grown green-manure crop in California. It is being grown
throughout the orchard sections wherever green-manure crops are
being used at all (see fig. 3). It is adapted to quite varied con-
ditions and succeeds in all sections of the State. In the coast sec-
tions, as well as inland, it makes a good growth and does well on both
the light and the heavy soils.

"See E. W. Hilo:ard. Soils, pp. 19-21, 63, 12fi, and 394-396.
190

16

OKCHAED nRT-IT^N-MANURK CROPS IN CALIFORNIA.

The qualities of common vetch are such as to make it well adapted
for green-manure purposes, especially in citrus orchards, and
orchardists in general are growing it in preference to field peas, which
were largely grown a few years since.

Common vetch makes a vinelike growth similar to that of peas, but
the vines are less succulent and so are able to stand considerable hard
usage without much injury. Thus, in orchards when picking fruit
and doing other work, the trampling which is unavoidable interferes
but little with the growth of the vetch. The root system, which is
quite extensive, lies largely near the surface and ordinarily is well
covered with nodules.

':LA^'J^ZjJ:

Fig. 3.— View in an orange orchard in southern California, showing common vetch grown as a green-
manure crop.

Wlien used for a green-manure in southern California common
vetch is usually sown during September and the first half of October.

However, better results are being secured with the earlier seedings,
and in most years to obtain the best results it is quite essential that
the crop be sown during the first half of September. Wlien thus
sown the plants make a good growth before cold weather and continue
to grow during the winter. But if the seed is sown late and the
plants have made but a small growth before the cold weather, they
then make little or practically no growth until the warmer weather
comes in the latter part of tJie winter.

190

WINTER GREEN-MANURE CROPS. 17

In February, 1908, at Redlaiids, Cal., which is representative of the
citrus sections, phmtings of vetch made in September, 1907, were from
12 to 15 inches high and in a fine condition to turn under. Plantings
made in October, 1907, from a month to six weeks Later, were but
6 inches higii. During the past season similar results were noted.

The rate of seeding varies from 40 to 60 pounds per acre. Forty
pounds per acre has been more generally recommended, but the
heavier seeding is giving much better crops and more than makes up
for the difference in the cost of the seed.

Early as well as heavy seeding is quite commonly recognized by
growers as necessary for obtaining the best results, and a deeper
seeding has also been found essential where the plantings are early.
In northern California under irrigation, vetches sliould be sown about
the first of October. They will then make sufficient growth to be
turned under in February or March. This later season of planting
in the northern part of the State is desirable in both citrus and
deciduous orchards on account of the heavy winter rainfall, which
does not permit turning under the crop as early as in the southern
section. Later planting in the deciduous-orchard sections is also
desirable on account of the possible injury from frosts when an early
succulent growth is made, as would be the case with earlier plantings.

Experiments and observations have shown that vetch will make
but little growth by February or March when sown in the fall without

irrigation.

CANADA FIELD PEAS.

The field pea was among the first crops tried in California for green
manuring and was the first one extensively used for this purpose.
Its early use was partly due to the fact that seed was readily obtain-
able. At the present time it still holds a prominent place as a green-
manure crop, and next to common vetch is most extensively used
(see fig. 4).

Like the common vetch the field pea is adapted to varied conditions
and has succeeded wherever green-manure crops have been grown.
For making a growth during cool weather there is no other crop
known that equals it; but it has other characteristics that make
it less desirable for green manuring, especially in citrus orchards.

The root s\^stem of the field pea, which is very extensive, consists
of a central or main taproot from which radiate the many finer
laterals. The roots extend (juite deep, and for this reason the crop is
favored by many orchardists for breaking up "plow sole."

The vines, which are succulent and tender, are greatly damaged by

the trampling necessitated during the harvesting of most citrus fruits;

and on account of their making so much new growth during cold

weather they are often severely injured by frost. Usually as the

52810°— Bull. 190—10 3

18

ORCHARD GREEN-MANURE CROPS iN CALIFORNIA.

plants approacli maturity the lower portions of the stems become
dry and wiry, making the turning under difficult.

Apliids, or plant lice, are very fond of peas and nearly ever}-^ year
their attacks occasion considerable damage. In the coast sections or
those having more humid conditions, the crops also suffer severely
from the attacks of mildew. Inland, however, there has been but
little injury from this cause.

Wliile field peas are in some ways objectionable they also have
certain qualities that make them serve special purposes. Their
ability to stand late fall planting and still produce a fair winter
growth makes them especially valuable for such use when for any

Fig. 4.— View in an orange orchard in southern California, showing Canada field peas grown as a green-
manure crop.

reason an earlier planting of other crops has not been accomplished,
but if sown late only a very ordinary crop can be expected. While
peas may be planted from the middle of September to the end of
November, in southern California the best results are secured from
September plantings. In the northern part of the State the middle
of October is better for planting because the winter rains prevent the
crop from being turned under until later in the winter. AVlien planted
early, peas in the north are also likely to suffer more severely from
winter frosts.

Seventy pounds of seed per acre is the usual rate of seeding.
This in some cases gives a very gootl crop but a thin stand, and
therefore a light yield has been very noticeable in all orchard

190

WINTER GREEN-MANURE CROPS. 19

sections. At least 80 pounds of seed per acre should be used, and
unless seeding conditions are very favorable more rather than less
is recommended.

During the past few winters the general crops of field peas and
vetch throughout the orchard sections of California have shown
that peas make a stronger individual plant growth than vetch, but
do not make as heavy a yield of green manure. When sown during
the latter part of September the peas have made a growth of from
24 to 36 inches, while common vetch made from 15 to 18 inches.
This is representative of the usual comparative stem growth of the
two crops. In the citrus orchards of southern California peas should
be turned under earl}^ in February, and in the northern part of the
State during the latter part of February or the first of March.

BUR CLOVER.

There are a number of kinds of bur clover, of which only two
are yet much grown in California, namely, the common or toothed
bur clover {Medicago hispida denticulata) and the spotted bur clover
(Medicago arahica). The toothed bur clover is the one most com-
monly seen, being thoroughly naturalized, but the spotted bur
clover, though less abundant, grows equally well. It differs from
common bur clover in having a brown spot on each leaflet and
longer and softer spines on the burs.

Bur clover makes a decumbent growth, the stems being rather
small and ciuite succulent when young, but it withstands considerable
trampling. The roots are shallow but numerous and usually have
many nodules. The crop has been grown to quite an extent for green
manure, but on account of its not making a good early-winter growth
its use will always be limited. In orchards where bur clover has
been once planted it will spring up for several years. This is due
to the hard seeds that do not germinate the first year. In the citrus
orchards of southern California bur clover is sown at the same time
as vetch, which is during September and early October. To obtain
the best results, seeding as early as possible in September is advised.
Twent\^ pounds of seed (hulled) per acre should be used, care being
taken to plant shallow, as deeply covered seed will not germinate
but will hold over in the soil. The sowing of seed in the bur is not
recommended, because the bur delays germination and occasions
very uneven stands, to say nothing of the greater difficulty in sowing.
However, there is no longer need of using seed in the bur, as clean
.seed can be secured in quantity from western seedsmen.

For use in deciduous orchards bur clover is of considerable import-
ance and if properly handled will serve a very useful purpose. At the
present time it is utilized only where it volunteers as a weed and
can be turned under at the regular spring plowing of the orchard.

190

20

OECHARD GREEN-MANURE CROPS IN CALIFORNIA,

On account of the light growth usually made by a green-manure
crop sown in the fall without irrigation, the expense of seeding a
crop each year in this way is hardly justified. Through the use of
bur clover this objection can be overcome by allowing the crop to
reseed itself from year to year. Tn this way with a little care bur
clover can be maintained in an orchard at small expense. If an
occasional late season prevents the crop from ripening its seed before
the orchard must be plowed, narrow strips can be left between the

rows to mature, and
in this way reseed-
ing be accomplished.
The fact that the
seeds of bur clover do-
not all germmate the
first 3"ear but hold
over in the soil imtil
the second or third
year, or even longer,
lends to the ease
of maintaining the
stand.

Bur clover is at
present most com-
monh" introduced
and maintained in
orchards by the use
of manure from old
sheep corrals, which
usually contains 1 arge
quantities of the seed.

FENUGREEK.

Fenugreek ( Trigo-
nellafoenum-graecum)
is an upright-growing

Fig. 5.— An indi\'ichial plant of fonugreek, showing Us characteristics. -, ., . ,i„„l

plant havmg a central
stem which is more or less })ranched. A somewhat open top is formed
when fenugreek is grown as an indivitlual j^Umt (see fig. 5). When
grown in plats with little chance for individual development, but
few branches are formed. The plants attain a height of 20 to 30
inches. The leaves, of which there is a medium number, are trifoliate,
with cuneate or obovate thickish leaflets. The seeds, wdiich are borne
in long, pointed pods, are quite small (one or two lines long) and of
a brownish-yellow color. The pods dehisce, or break open, tardily,
making the crop one that can be handled easily for seed.

190

WINTER GREEN-MANURE CROPS.

21

ADAPTATION.

Fenugreek is grown in quantity in California only in Ventura and
Orange counties. The recognition of its value as a green-manuro
crop dates back to 1903, it having been distributed the previous
year by the California experiment station. Since that time its use
has gradually increased, and while it is only in Orange and Ventura
counties that it has been used as a regular crop it has been tested
and grown in a small way in all the citrus sections of the State
(see fig. 6).

From tests and observations made during the past three years it
seems quite evident
that fenugreek is best
adapted to the citrus
sections of the State
having the imme-
diate coast influ-
ences. The climatic
conditions of such lo-
calities are very
favorable for fenu-
greek, and it is there-
fore in those sections
that it has attained
its best development .
In sections farther
from the coast, such
as at Riverside and
Redlands, and in the
interior valleys of the
State, quite g:oo(l

-4*:

'rm

'^T' TM'M\

Fig. G.— View in a walnut orchard in Orange County, California.
showin:; fenugreek grown as a green-manure crop.

te^

crops have been grown, but in such localities the crop is more exacting
in its requirements as to time of planting, etc.

COMPARATIVE VALUE.

In comparative tests made at Redlands, Cal., fenugreek sown
October 7, 1907, by the middle of February, 1908, had attained a
height of 10 inches. Common vetch made but 6 inches of growth in
the same time. At Pomona, Cal., fenugreek sown November 4.
1907, by the middle of February, 1908, had made a growth of
18 to 24 inches. Common vetch in comparison made but 8 inches
of growth during the same time. At Chico, in northern California,
fenugreek sown October 5, 1908, with irrigation, by the first of
March, 1909, had made a growth of 12 to 15 inches, and of 16 to
20 inches by the middle of March. In other te.sts the fenugreek did

100

22 ORCHARD GREEN-MANURE CROPS IN CALIFORNIA.

not make so good a showing, yet wherever sown early it has done
quite well.

As to the quantity of green manure produced by fenugreek in
comparison with other crops there are but limited data. At Santa
Paula, Cal., weights of vetch and fenugreek were taken the middle
of February, 1909, to determine the quantity of green manure pro-
duced. The plants growing in the space between four trees were
cut and weighed green, and the yield per acre was computed from these
weights. The fenugreek yielded 11,745 pounds per acre solid area,
or 8,432 pounds orchard area, while the common vetch yielded
19,140 pounds per acre solid area, or 13,742 pounds orchard area.
However, these figures do not justly represent the comparative yield
of organic matter, as the moisture content of the vetch was undoubt-
edly nmch greater than that of the fenugreek, and the yield of dry
matter of the two crops would have been much more nearly equal
than is indicated by the figures given. At Chico, in northern Cali-
fornia, fenugreek weighed green March 16, 1909, yielded at the rate
of 13,721 pounds per acre. This w^as from plantings made October 5,
1908. In comparison, at Chico, conunon vetch produced but 2,831
pounds per acre.

Considering the convenience and cost of handling, fenugreek is
superior to any other green-manure crop now being used. The
upright habit of the plant makes the crop easy to turn under. The
roots have many nodules and form a s^^stem similar to that of the
field pea.

Fenugreek is especialh" desirable for an orchard green-manure
crop, owing to the fact that no insect pests seem to be harbored by
it. This point has been especially noticeable in sections where the
army w^orm, harbored in such crops as vetch, bur clover, and field
peas, has done considerable damage to fruit. During the season of
1907, orchards in which fenugreek was being grown were noted as
being free from the army worm, while other orchards in the same
section were quite badly infested.

PLANTING.

No special preparation of the land is necessary for planting fenu-
greek. A seed bed such as is desirable for ordinary field crops is
all that is required. The best time for seeding varies somewhat in
the different parts of the State. For a winter green-manure crop in
southern California, in sections aw^ay from the coast, such as Pomona
and Redlands, plantings should be made as early in September as
possible. In sections near the coast plantings may be made later
with good results, but September planting is to be advised. In
northern California plantings for green manure should be made the
first of October.

100

WINTER GREEN-MANXJEE CROPS. 23

Fenugreek does best on a good, deep loamy soil, but such a soil is
not necessary for success, as the plant does quite well on a gravelly
or a sandy soil. It is not adapted, however, to a soil that will become
hard, like heavy clay or adobe. The cx'op should be sown either
broadcast or in close drills. Thirty pounds of seed per acre is neces-
sary for a green-manure crop, while less is best for a seed crop. Care
should be taken not to plant the seed too deep.

SEED PRODUCTION.

The fenugreek seed handled by American seedsmen is almost
entirely imported. The demand for it has been so slight that only
small stocks are handled. The imported seed comes from the Medi-
terranean countries, chiefly from Egypt and Palestine. The seed
of fenugreek used in the orchard green-manure work in California is
grown almost entirely in Orange and Ventura counties, in which
localities a good crop of fine seed can be produced.

Possibly the only sections where fenugreek can be grown profitably
as a seed crop are where the winters are ver}^ mild, having at most light
frosts, so that mth late fall seeding there will be a sufficient growth
made during the winter months. An ordinary grain drill is the best
implement to use in seeding. From 15 to 20 pounds of seed per acre
are sufficient. After seeding, nothing is done with the crop until it
is harvested. In the interior valleys an irrigation at the time of
seeding is necessar}-.

The crop can be cut with an ordinary mower, and after a short time
should be raked into windrows. Here it should be allowed to cure
for several days before thrashing, which can be done with an ordinary
thrashing machine. In so far as possible the crop should be taken
from the windrows in the early morning, there being less shattering
of the seed when handled at this time. The pods when very dry
drop from the stem and dehisce, or break open slighth^, although
the loss of seed from this cause is not great.

The quantity of seed produced per acre varies as with any other
crop, and while there are few definite figaires as to 3'ields, in Ventura
and Orange counties, where the best fenugreek seed crops are produced,
probably 1,500 pounds per acre is an average yield. At Chico, in
northern California, plantings in ^V-acre plats yielded at the rate
of 490 pounds of seed per acre, while one smaller plat yielded at the
rate of 1,315 pounds per acre. The Chico plantings were made with
irrigation the first half of October, 1908. The crop was harvested
the 1st of June, 1909.

HAIRY VETCH.

The hairy or winter vetch ( Vicia villosa) is not so well adapted for
green-manure purposes as is the common vetch, and it has not been
used except in a A^ery limited way. Under California conditions it

100

24 OKCHAKD GEEEN-MANUKE CROPS IN CALIFORNIA.

makes less growth during the winter season than the common vetch^
and this has prevented its larger use for green manuring. Extensive
experimental tests in comparison with common vetch, as well as
practical tests made by orchardists, show the same results.

While hairy vetch does not make a good winter growth, when the
warmer weather of the latter part of winter and early spring comes,
it makes a very vigorous start and, if left to develop fully, a heavier
growth than common vetch. It also stands more dry weather without
injury, and where a late spring crop is wanted it is very desirable.
The handling of the crop is the same as with common vetch. From
45 to 50 pounds of seed per acre should be used in seeding.

INDIAN MELILOT.

Indian melilot {Melilotus indica) is quite common in waste places
throughout the orchard sections of southern California and for a
number of years has received some attention as a green-manure
crop. However, it has never been used except in a very limited or
experimental way, and this experience indicates that it has but
very little value in orchard work in California.

The winter growth of melilot is about like that of bur clover, and,
like that crop, its best growth is not made until too late in the
winter to be turned under in February. The only place in California
where melilot seems likeh' to prove at all valuable is on the very
sandy soils, to which it is quite well adapted and on which it is often
hard to get a stand of other green-manure crops.

SUMMER GREEN-MANURE CROPS.

The question is sometimes asked whether it is advisable to grow a
summer green-manure crop as well as a winter crop, thus enabling
one to add two crops a year to the soil instead of one. Where water
for irrigation is available there is no difficulty in doing this. How-
ever, the practice is not to be advised except under very exceptional
conditions. The enormous quantity of water used by a green-manure
crop in its growth makes it decidedly objectionable for summer use
in an orchard, where all the water available is usually needed for the
orchard crop.

The growing of a summer green-manure crop also necessitates the
discontinuance of cultivation of the soil, which except on the most
open soils would be more or less detrimental if continued for a long
period. There may be instances, however, where it is desirable to
build a soil up as rapidly as possible. In such cases a summer green-
manure crop may be used to advantage. For this purpose the
Whippoorwill variety of cowpea has been found the best of any crop
tested.

190

KESULTS OF TESTS WITH VARIOUS LEGUMES. 25

RESULTS OF GREEN MANURING IN CALIFORNIA.

There have been no definite tests made in Cahfornia to determine
the results in an increased yield of fruit or improved quality of the
same from the use of green manures. The only evidence available
is that of general observation and the experience of the orchardists.

While orchardists differ to some extent in conclusions, they gener-
ally are favorable to the practice, as its continued and growing use
attests. Careful observations also show the beneficial results of
green-manure crops in a more thrifty appearance of the trees, an
improved condition of the soil, and a better quality of the fruit.
The belief is quite general that the yield, also, is increased. Orchards
in which a few years ago there were unthrifty trees with yellowish-
colored leaves now, after several years' use of green-manure crops,
show a decided improvement in color and general appearance. The
work of the California experiment station has demonstrated that
gummosis of citrus trees is brought on by unfavorable soil conditions
and that in remedying such conditions green manures serve a very
useful purpose.*^ Orchards in w^hich green manures have been used
for a long time are but little affected by this disease.

The improved condition of the soil when green manures have been
used for some time has been readily noticeable to those handling an
orchard. The heavier soils have become quite open and friable and
the sandier soils more loamy. Beneficial results in the conserving
of rainfall and the prevention of washing of the soil have also been
very apparent. Most soils that wash badly do so because they are
deficient in organic matter. Green manuring, by the improvement
of the mechanical condition of the soil, not only prevents washing,
but the presence of the growing crop on the land prevents gullying
during the rainy season. This is of particular importance on sloping
lands.

RESULTS OF TESTS WITH VARIOUS LEGUMES.

From the fact that the addition of humus to the soil is one of the
main objects in using a green manure, it necessarily follows that,
other things being equal, the crop producing the heaviest vegetative
growth is the most desirable. To determine the comparative
amount of vegetative growth made by various crops the green weight
per acre has been determined, as shown in Tables I, II, and III.
However, these figures can be taken only as indicating in a general
way the amount of organic matter returned to the soil, as no correc-
tions were made for the varying moisture content of the different
crops.

a Bulletin 200, California Agricultural Experiment Station. 1908.
190

26 OKCHAED GEEEN-MANURE CROPS IN CALIFORNIA.

In Table II the weight of the green material produced per acre is
presented, together with the weight of the same when dry. The
green material was weighed at the time of cutting, and for estimates
of the yield of dry matter was weighed again in thirty days. During
this period the various crops had become nearly dry, but undoubt-
edly the moisture content, even at this time, would vary to some
extent, although not nearly so much as in the green state.

That the yield of green material as shown by its weight may be
misleading without proper correction for the moisture it contains is
shown in Table II in the case of the two lots of black-purple vetch. The
first lot was quite succulent at the time of cutting, and consequently
was very heavy in the green state, while the other was a little older and
less succulent, and so was much lighter. The latter did not show the
heavy loss in drying that the former did, however, and thus the dif-
ference in the amount of organic matter of the two is not nearly so
great as the difference in the weights of the green matter would indi-
cate. In this connection it should also be noted that varying yields
are often due to a difference in the stands rather than to differences
in the growth of the crop. In the comparative data presented in
the tables this has been reduced to a minimum by selecting for this
purpose crops with as nearly uniform stands as possible.

From all data available it seems clear that of the commonly grown
green-manure crops, vetch, peas, bur clover, and fenugreek, the
vetch returns the most organic matter to the soil and the peas the
least. The light yield of peas is not due to a lack of stem growth,
which on the contrary is always good, but to the generally poorer
stand and more open habit of growth. Bur clover, while weighing
heavy green, is very succulent when young, and when compared with
an equal weight of green vetch represents much less organic matter.
Fenugreek yields well, but not so much as vetch.

In securing the yield of green manure per acre, as presented in
Table I, the plants growing on a plat 6 by 20 feet were cut and
weighed green and the yield per acre computed from these weights.
In Table II a plat 10 by 10 feet square of each crop was cut and
weighed green and the yield per acre thus calculated. The same
was weighed again in thirty days, as shown in the table, giving the
yields of the dry matter. In Table III the weights shown were
taken from crops being grown by orchardists during the winter of
1908-9 at the places mentioned in the table and are representative
of these crops as grown under actual orchard conditions. To obtain
the results the plants growing on a space between four trees were cut
and the yield per acre calculated from such weights.

190

PROMISING GEEEN-MANUEE CEOPS.

27

Table I.— Growth of plants and weight per acre of green-manure crops sown with irriga-
tion October 19, 1907, at Chico, Cal.

Name.

Black bitter vetch....

Black-purple vetch..

Woolly-podded vetch

Hairy vetch

Common vetch

Lathyrus sativus

Tangier pea

Field pea

Horse bean

Height of

Rate of

plants,

seeding.

March 18,

1908.

Pounds.

Inches.

1 130
\ 34

26

26

f 56
I 34

30

30

17

28

56

15

39

12

56

16

56
159

1(34

18
26

28

Weight of
green ma-
nure, March
28, 1908.

Pounds.
32,056
23, 236
24,042
15,609
18, 876
11,616
7,623
19, 239
13,794
15,944
10,890

Table II —Growth of plants and iveight per acre of green-manure crops sown with irriga-
tion October 5, 1908, at Chico, Cal.

Name.

Black-purple vetch..

Woolly-podded vetch

Black bitter vetch...

Horse bean

Fenugreek

Tangier pea

Bur clover

Hairy vetch

Common vetch

Rate of
seeding.

Pounds.

f 62

[ 45

48

f 76

[ 49

149

29

72

21

31

33

Height of

plants,

March 15,

1909.

Inches.

32-36

36-40

30-36

20-22

20-22

30-36

16

17

14-16

8-15

10-18

dry mat

ter, March

16, 1909.

Weight of Weight of

Pounds.
40, 565
14,374
25, 047
27,660
14,374
21,130
13,721
12, 840
11,980
5,880
2,831

dry mat
ter, April
10, 1909.

Pounds.
3, 075
2,321
2,933
3,776
2, 130
2,634
1,783
1,646
735
871

Propor-
tion of
dry to
green
matter.

Per cent.

9.0
1G.8
11.7
13.6
14.8
12.4
12.9
12.8

6.1
14.8

Table III.— Weight of green-manure crops growing in orange orchards in California.

Name.

Tangier pea

Common vetch

Malva rotundifolia.

Bur clover

Field pea

Fenugreek

Common vetch ....

Place.

Redlands

....do

....do

do

....do

Santa Paula.
do

Weight of
green mat-
ter per acre.

Pounds.
29,093
13, 578
19,800
16,347
7.260
11,745
19, 140

Weight of
green mat-
ter per 0.718
acre.o

Pounds.

20,888
9,749

14,216

11,737
5,212
8,432

13,742

a This equals the part of an acre usually covered by a green-manure crop in an orchard.

PROMISING GREEN-MANURE CROPS.

As shown by Tables I and II, giving comparative yields, there
are several plants very promising for green-manure purposes as com-
pared with common vetch and field peas. The claim of superiority
for these plants is largely due to their ability to make more growth

ivto

28

ORCHAED GREEN-MANURE CROPS IN CALIFORNIA.

during the cool weather of the winter, thus affording a heavier growth
to be turned under. This is an especially strong point where it is
desirable to turn the crop under as early as possible, as is the case in
the citrus orchards of southern California. The plants referred to
are the black-purple vetch, the black bitter vetch, the woolly-podded
vetch, the horse bean, and the Tangier pea.

BLACK-PURPLE VETCH.

The black-purple vetch (Vicia atrojmrjmrea) is one of the most
promising green-manure crops tested for California. Its general

Fig. 7.— a field of black-purple vetch at Chico, Cal.

appearance and habit of growth are about like those of the com-
mon vetch (fig. 7), although it is very distinct from that species.
The superior value of black-purple vetch when compared with com-
mon vetch lies in its ability to make a much stronger growth during
the cool weather of early winter. This, as noted elsewhere, is an
especially desirable quality in a green manure to be turned under in
February,

The root system of black-purple vetch, which is similar to that of
common vetch, is well covered with medium large nodules. The
stems, aside from making a strong growth, are of such a texture as

190

PROMISING GREEN-MANURE CROPS.

29

to enable them to stand much tramphng or other hard usage without
injury.

The time and manner of seeding tliis crop are much the same as
with common vetch. As the seed is a httle smaher, however, a
smaller quantity may be used in seeding. From 50 to 60 pounds per
acre is advised.

BLACK BITTER VETCH.

Black bitter vetch (Vicia ervilia), another very promising green-
manure crop for California, is different from most other vetches in
that it is upright in its habit of growth, rather than vinelike. Like

''A}-:'-^r^^^^:^:Ji:.

Fig. 8.— a field of black bitter vetch at Chico, Gal.

the black-purple vetch, it possesses the desirable quality of making a
good growth during the cool weather of early winter and is much
superior to common vetch in this respect. (See fig. 8.) In this
connection it should be noted that different strains of this vetch
have given different yields, so that some will doubtless be found
superior to others. ■'-'•'

Its upright habit of growth makes this crop very easy to turn under
with an ordinary moldboard plow. The viny growth of common
vetch makes it objectionable to some orchardists. The root system,
while quite well covered with nodules, is perhaps not so extensive as
that of some of the other vetches. The plant has a more definite

190

30 OECHARD GREEN-MANUEE CEOPS IN CALIFOENIA.

central root, or taproot, than common vetch, and the fibrous roots
tend to penetrate more deeply. The seeding habits are much better
than those of other vetches. The pods shatter but very little, which
much facilitates the harvesting of the seed.

Black bitter vetch is grown very extensively in the Mediterranean
region, where the seed is a commercial product. The fact that the
seed of this plant can be imported at a reasonable cost makes it pos-
sible to supply the trade at once. On account of the plant branch-
ing but little it is necessary to use a slightly larger quantity of seed
in seeding than with common vetch. Seventy pounds per acre is
recommended. Aside from the quantity of seed per acre used, the
crop should be handled like common vetch.

WOOLLY-PODDED VETCH.

Woolly -podded vetch (Vicia dasycarpa) resembles hairy vetch
quite closely, both in appearance and in agricultural value.

In comparative tests the woolly-podded vetch has made a stronger
growth during the cool weather of early winter than the common or
the hairy vetch, but not so strong as the black-purple vetch or the
black bitter vetch. As soon as the warmer weather of the latter part
of winter comes it is one of the most vigorous growers and its ultimate
yield is very heavy. Thus, while it will serve very well as a crop to
be turned under in early winter its special value is for conditions where
the crop can be allowed to remain a little later in the spring. For
sowing without irrigation in deciduous orchards it may be of special
value.

Woolly-podded vetch stands trampling well and for orchard use
is in this respect ec[ual, if not superior, to common vetch. The root
system is about like that of common vetch and is well covered with
medium large nodules.

In growing woolly-podded vetch it should be handled as common
vetch, except that a little less seed may be used in seeding. Fifty
pounds per acre is sufficient.

HORSE BEAN.

The horse bean (Vicia faba) has been but little grown in California.
The broad bean, however, which differs from the horse bean only in
having larger and broader seeds and pods, has been grown as a vege-
table for a number of years in a few localities.

Experimental tests in California during the past few years indicate
that the horse bean has considerable value as a green-manure crop,
especially in the southern part of the State. (See fig. 9.)

The plant has an upright stem which is quite leafy, but little
branched. The leaves, as well as the stems, are quite large, but com-

190

PROMISING GEEEN-MANUEE CEOPS.

31

paratively soft and succulent until well matured. The root system
consists of a strong taproot, with a fairly well-developed fibrous sys-
tem radiating from this. The roots penetrate quite deeply into ordi-
nary soils and aid in overcoming "plow sole." The taproot, as well
as the smaller roots, when well inoculated has many large nodules,
indicating that it is a good nitrogen gatherer. In southern California
horse beans are usually well inocvdated and have many large nodules.
In northern California, thus far, they have had very few or no nodules
the first year they have been grown. Consequently, when grown
without artificial inoculation they amount to but little, although when
inoculated they succeed quite well.

Fig. 9.— View in a citrus orchard in southern California, showing horse beans grown as a green-manure crop.

Although the stems of the horse bean are quite large they decom-
pose readily when turned under for green manure. In comparison
with other green-manure crops horse beans make a good growth, but
in an orchard will not withstand trampling like the vetches. As the
seeds are large a considerable quantity is required in seeding, unless
the field is planted in drills more than the ordinary distance apart. As
the individual plants make a comparatively large growth they will
stand this method of planting, and if sown in drills IS or 24 inches
apart a good yield will be secured. The season for planting is the
same as that of vetch.

190

32 OECHARD GKEEN-MANURE CROPS IN CALIFORNIA.

TANGIER PEA.

The Tangier pea {Lathyrus tingitanus) was originally introduced into
this country from northern Africa. It is an annual legume resembling
in general the garden sweet pea, to which it is related.

During the past few years considerable attention has been given to
the Tangier pea to determine its value as a green-manure crop, and
results thus far indicate that it is of considerable value for this pur-
pose. It makes a strong growth, yielding a heavier tonnage per acre
than the common vetch (see Tables I, II, and III). Its dense growth
enables it to overrun and smother out weeds, which is one of the very
noticeable qualities of this crop. Though the stems are quite large
they are not very succulent and stand considerable rough usage,
being well adapted for orchard use in this respect. The large growth
made by Tangier peas makes them somewhat difiicult to turn under
with an ordinary moldboard plow; with a disk plow but little trouble
in this respect will be experienced.

The root system is well developed. It has a more nearly definite
central root than vetch, and the roots penetrate the soil more deeply.
The nodules are large and numerous, indicating that the plant is a
good nitrogen gatherer.

For a green-manure crop Tangier peas should be handled like com-
mon vetch, except that the seeding should be heavier, from 70 to 75
pounds of seed per acre being required for obtaining the best results.

COST OF SEED OF GREEN-MANURE CROPS.

The cost of seed of green-manure crops is a factor of considerable
importance in determining their relative value. The high price of
seed may be the cause of the elimination from use of an otherwise
good crop. In most orchard sections it is hardly practicable for the
orchardist to attempt to raise his own seed, though with crops having
good seeding habits this could be readily done. The commercial seed
grower will very likely be depended upon for the supply of seed needed.
The price that growers will pay for any new crop will probably be
largely determined by the price of seed of common vetch and of field
peas. A slightly higher price for a superior crop would undoubtedly
be paid. However, a superior crop and cheap seed are what is
desired.

The practice of allowing enough seed to ripen in the orchard to
volunteer a crop from year to year is the cheapest method of seeding
a green-manure crop, but this is practicable only in deciduous orchards
without irrigation, where the returns will justify but very little
expense in connection with such a crop. Under such conditions bur
plover in particular can be effectively used.

190

COST OF SEED OF GREEN-MANURE CROPS.

33

Table IV. — Seed 'production per acre of various legumes at Chico, Cal., 1909. Plats

one-twentieth acre.

Name.

Tangier pea

Tangier pea

Fenugreelj;

Fenugreek

Black bitter vetch

Black bitter vetch

Black bitter vetch

Black-purple vetch...
Black-purple vetch...
Black-purple vetch...
Black-purple vetch. . .
Woolly-podded vetch

Rate of
seeding.

Pounds.
72
77
28
21
48
45
70
58
36
36
48
45

Yield
of seed.

Pounds.
210
630
490
490
600
1,800
1,980
300
380
580
400
290

In Table IV is presented the seed yield of various new green-manure
crops discussed in this bulletin. These yields were taken from g^o-acre
plats that had been sown primarily for a green-manure crop test
and not for seed production. So the yields in some instances are
much hghter than would have been the case had the crop been sown
for seed.

It is quite probable that at Chico, where these crops were grown,
conditions are not so favorable for the seed production of such plants
as the woolly-podded vetch and the black-purple vetch as are the
conditions in western Oregon, where seed of common vetch and hairy
vetch is grown commercially. This is probably also true of the Tan-
gier pea, though not so much so of the black bitter vetch, which
does well at Chico. The yields presented in the table and the gen-
eral character of the crops indicate that seed should be produced
as cheaply as that of common and of hairy vetch, and in the case of
black bitter vetch somewhat more cheaply. The seeding habits of
black bitter vetch are such that an orchardist could easily raise his
own seed if necessary, and where it is desirable to grow some crop
in a young orchard he might raise the seed with profit.

Of the crops mentioned, the production of seed will cost most
with the Tangier pea and the woolly-podded vetch, and least with
the black bitter vetch. The cost of seed of common vetch and field
peas varies from year to year. Seed of common vetch during the
past few years has varied from 3^ to 5 cents per pound. When
seeding at the rate of 60 pounds to the acre this woukl make the
cost of seed from $2.10 to $3 per acre.

Seed of field peas has been about the same price per pound as
that of common vetch, but as 80 pounds of seed per acre are needed
in seeding, this makes the cost from $2.80 to $4 per acre.

Bur clover seed is advertised at from 25 to 30 cents per pound,
hulled. When seeding at the rate of 20 pounds of seed per acre this
makes the cost of seed from $5 to $6 per acre.

190

34 OECHAED GEEEN-MANUEE CROPS IN CALIFOENIA.

The wholesale price of fenugreek seed in the European market is
from 2^ to 3 cents per pound. The price to the grower would of
course be somewhat in advance of this, but should not exceed 5 or
6 cents. Wlien 30 pounds of seed per acre are used, this would make
the cost of seeding from $1.50 to $1.80 per acre.

Black bitter vetch seed, though not handled in quantity by Ameri-
can seedsmen, can be secured m foreign markets and imported at a
cost that should make the price to the grower about the same or
less than that of common vetch. When seeding at the rate of 70
pounds of seed per acre, this would make the cost of seeding from
$2.40 to $3.50 per acre. As stated elsewhere, the fact that black
bitter vetch yields a heavy crop of seed in California and has excep-
tionally good seeding habits should make it possible to place Cali-
fornia-grown seed on the market at a much less cost than that of

common vetch.

SUMMARY.

California soils, though often very fertile, are generally deficient in
humus.

Within recent years green-manure crops in California have been
given special attention.

The only places where green manures are being used extensively
are the citrus and walnut orchards of the southern part of the State.

Deciduous orchard sections of the State are using practically no
green-manure crop.

By the use of green manures a generally improved condition of
orchards has been secured, as shown by a more healthy appearance
of the trees and more and better fruit.

The early seeding of green-manure crops is desirable for obtaining
the best results.

Green manures should be turned under before the trees start new
growth in the spring.

Heavier seeding than is ordinarily practiced is advised.

Common vetch and field peas are the most generally used green-
manure crops, the vetch being the most popular.

Peas or common vetch sown in the fall without irrigation will not,
except in the most favorable years, make sufficient growth to be
turned under early as a green manure, but when thus sown will
make a good growth later in the spring.

Field peas, common vetch, and bur clover are adapted to quite
varied conditions, and are being grown in a limited way throughout
the State.

In any part of the State having a mild winter a green-manure
crop of peas or common vetch will succeed if sown early in the fall
with irrigation.

190

SUMMARY. 35

Bur clover seems to be of most value for deciduous orchard con-
ditions, while the woolly-podded vetch promises to be of value for
the same conditions.

Fenugreek and bur clover are used to a limited extent, fenugreek
being especially adapted to the region near the coast.

Hairy vetch is not well adapted for use as a green-manure crop in
California.

Black bitter vetch, black-purple vetch, woolly-podded vetch, horse
beans, and the Tangier pea are promising new green-manure crops
in comparison with common vetch.

Green-manure crops need no inoculation in California, horse beans
in the northern portion being the only known exception.

The growmg of a summer green-manure crop in California orchards
is not advisable.

Local as well as sectional conditions in the various parts of the
State vary considerably, and must be taken into consideration in
determining the best crop for green manure as well as the best method
of handling the same.

190

INDEX.

Page.

Acids, vegetable, relation to availability of plant food 15

Alfilaria, use as green manure '. 7

Alfilerilla, synonym of alfilaria 7

Aphids, damage to green-manure crops 18

Army worm. See Worm, army.

Bean, horse, inoculation in green manuring 14, 35

nitrogen-gathering status 31

use as green-manure crop 26, 27, 30-31, 35

Black bitter vetch. See Vetch, black bitter,
purple vetch. See Vetch, black-purple.

Brome-grasses, use as green manure 7

Bur clover. See Clover, bur.

California, orchard districts 8-10

southern, inoculation with nitrogen-gathering bacteria 31

summary, green-manm-e crops 34-35

University, work with green-manure crops 7

Canada field peas. See Peas, Canada field.

Chico, Cal., Plant Introduction Garden, tests 7

results for green-manure crops 21, 22-23, 27, 33

Citrus orchards. See Orchards, citrus,
trees. See Trees, citrus.

Clover, bur, nitrogen-gathering status I9

use as green-manure crop 7, 9, 12, 15, 19-20, 26, 27, 32, 34, 35

Commercial fertilizers. See Fertilizers.

Cowpea, Whippoorwill, use as green-manure crop 24

Crops, green manure, conditions of use 10, 11

nitrogen-gathering status 16, 19, 22, 28, 29, 30, 31, 32

promising, discussion 27-32

qualities and methods 10-15

results of growing 25-27

summary for California orchards 34-35

summer, objections and suggestions 24, 35

turning under 12-13

winter, use in California orchards 15-24

Deciduous orchard sections. See Orchards, deciduous.

Drought, endurance by hairy vetch 24

Dry weather. See Drought.
Erosion. See Soil, erosion.

Exeter, Cal., center of citrus-fruit area g

Fenugreek, freedom from insects harmful to orchards 22

nitrogen-gathering status 22

seed 22, 23, 33, 34

use as green-manure crop 15, 20-23, 27, 35

190 37

38 ORCHAED GEEEN-MANUEE CEOPS IN CALTFOENIA.

Page.

Fertilizers, commercial, use with green manuring 15

Field peas, Canada. See Peas, Canada field.

Fresno County, Cal., area in northern citrus district .' 8

Frosts, danger to green-manure crops 8, 17

Green-manure crops. See Crops, green manure.

Gummosis, citrus disease, remedy by green manuring 25

Hairy vetch. See Vetch, hairy.

Harrow, disk, use with green-manure crop 11, 12

Horse beans. See Beans, horse.
Indian melilot. See Melilot, Indian.

Inoculation, use in green manuring 14-15, 31, 35

Insects, injurious, harbored in green-manure crops 22

Introduction to bulletin 7

Irrigation, use with green-manure crops 8, 9-10, 12, 17, 23, 27, 34

Land, preparation, green manuring in southern California 11-12

Lathyrus sativus, comparison as green-manure crop 27

tingitanus. See Pea, Tangier.

Legumes, seed production at Chico, Cal., table 331

use as green-manure crops 11, 13, 25, 27, 33

Lemon, orchard conditions unfavorable to green manuring 10

Lemoncove, Cal., relation to northern citrus district 8

Malva rotundifolia, yield of green manure 27

Manure, green, use in California 10-35

stable, usefulness on heavy soil 10

Medicago arabica. See Clover, bur.

hispida denticulata. See Clover, bur.

Melilot, Indian, use as a green-manure crop 15, 24

Melilotus indica. See Melilot, Indian.

Mildew, damage to green-manure crops 18

Nitrogen gathering. See Nodules.

Nodules, occurrence, on roots of nitrogen-gathering plants. . 16, 19, 22, 28, 29, 30, 31, 32

Northern citrus section. See Orchards, citrus.

Orange County, Cal., fenugreek as green-manure crop 21, 23

green-manure crops, results in orchards 27

Orchards, California, increasing use of green manure 25

citrus, green-manure crops 7, 34

southern section 8-9, 11-15, 34

deciduous, bur clover as green manure 19, 35

California, discussion 9-10, 34

geographic districts, California 8-10

walnut, southern California, green-manuring methods 11-15

Oroville, Cal., center of citrus fruit-growing area 8

Palermo, Cal., center of citrus fruit-growing area 8

Pea, Canada field, use as green-manure crop 7, 15, 17-19, 34

field, comparison as green-manure crop 26, 27, 34

seed, prices 33

time and rate of seeding for green manure 18-19

Tangier, nitrogen-gathering status 32

use as green-manure crop. 27, 32, 33, 35

Pin-grass, synonym of alfilaria 7

Plant food, availability, remarks 15

lice. See Aphids,
190

INDEX. ' 39

Page.
"Plow sole." See Roots, deeply penetrating.

Plow, use in turning under green-manure crops 11,12

Pomona, Cal., fenugreek, comparative tests 21

Porterville, Cal., relation to southern citrus district 8

Rainfall, California orchard districts, relation to green manuring 8-9, 10, 17

Rainy season. See Rainfall.

Redlands, Cal., plantings for green manure 17, 21

Roots, deeply penetrating, remedy for "jjlow sole" 17, 31

orchard tree, danger of disturbance in green-manure plowing 12

Sacramento Valley, area in northern California citrus district ' 8

San Joaquin Valley, relation to California citrus districts 8

Santa Clara Valley, irrigation for green-manure crops 12

Paula, Cal., fenugreek, comparative tests 22

Seed, cost for green-manure crops 32-34

green-manure crops, production 23, 32-34

Seeding, bur clover, time and rate 19

fenugreek, time and rate 22, 23

field peas, time and rate 18-19

methods in California 12, 32

recommendations 34

Tangier pea, time and rate 32

vetch, time and rate 17, 29, 30

Sierra Madre Mountains, relation to California citrus districts 8

Soil, California, lack of humus 34

orchard districts 8-9

erosion, prevention by green manuring 25

fenugreek 23

heavy, unfavorable to green manuring 10

improvement by green manuring 25

sandy, for Indian melilot 24

Southern citrus section. See Orchards, citrus.
Spring vetch. See Vetch, common.
Stable manure. See Manure, stable.

Summary, green-manure crops 34-35

Summer green manure. See Crops, green manure.
Tangier pea. See Pea, Tangier.

Trampling, relation to green manuring 11, 17, 19, 29, 30

Trees, citrus, cultivation, need, and effect of cessation 10

Trigonella foenum-graecum. See Fenugreek.

Turning under, time for green-manure crops 34

Vegetable acids. See Acids, vegetable.

Ventura County, Cal., fenugreek as green-manure crop 21, 23

Vetch, black bitter, nitrogen-gathering status 29

use as green-manure crop 26-27, 29-30, 33, 34, 35

purple, nitrogen-gathering status 28

use as green-manure crop 26-27, 28-29, 33, 35

common, nitrogen-gathering status 16

use as green-manure crop 12, 15-17, 22, 26-27, 34, 35

hairy, use as green-manure crop 15, 23-24, 26-27, 35

spring. See Vetch, common.

woolly-podded, nitrogen-gathering status 30

use as green-manure crop 26-27, 30, 33, 35

190

40 ORCHAED GREEN-MANUEE CROPS IN CALIFORNIA.

Vicia atropurpurea. See Vetch, black purple.

dasycarpa. See Vetch, woolly podded.

ervilia. See Vetch, black bitter.

faba. See Bean, horse. Page-

sativa, use as green-manure crop 15-17

villosa. See Vetch, hairy.
Walnut orchards. See Orchards, walnut.

Weather, southern citrus section, notes 8

Weeds, use in green manuring ^

Winter green-manure crops. See Crops, green manure, winter.

relation to vetch and peas for green manuring 34

Worm, army, harbored in green-manure crops 22

190

o

[Continued from page 2 of cover.] ;

No. HIT. Aiucririui Ivool l,)riij;s. Iyil7. J'riuc l.S cents. ^

108. The Cold Storage of Small Fruits. 1907. I'rice, 15 eonts. '

1(19. Anipriean Varieties of (iarden Beans. 1907. Priee, 25 eenls. ■ 1

1 10. Cranberry Diseases. 1907. Price, 20 centsT- j

112. U.soofSuiirareaal Glands in Testing of Drug I'lant.s. 1907. Price, 10 cents. 1

113. Tolerance of Plants for Salts Common in Alkali Soils. 1907. Price, 5 cents. j

114. Sap-Rot and Other Diseases of the Red Gum. 1907. Price, 2o cents. ■•
11.3. Disinfection of Sewage for Protection of Water Supplies. . 1907. Price, 10 cents. ;
110. The Tuna as Food for Man. 1907. Price, 2.5 cents. • ji
117. The Reseeding of Depleted Range and Native Pastures. 1907. Price, 10 cents. '
ll^i. Peruvian Alfalfa. 1907. Price, 10 cents. \

119. The Mulberry and Other Silkworm Food Plants. 1907. Price, 10 ceuls. ;

120. Production of Easter Lily Bulbs in the United Stales. 1908. Price, 10 cents.

121. Miscellaneous Papers. 190S. Price, 15 cents. :

122. Curly-Top, a Disease of Sugar Beats. 1908. Price, IB cents. '
12.3. The Decav of Oranges in Transit from California. 1908. Price, 20 cents '

124. The Prickly Pear as a Farm Crop 1908. Price, 10 cents. i

125. Dry-Land Olive Culture in Northern Africa. 190S. Price, 10 cents. "
120. Nomenclatm-e of t\ie Pear. 1908. Price, 30 cents. '
12,. The Improvement of Mountain Meadows. VJOS. . Price, 10 cents. i

128. Egyptian Cotton in the Southwestern United Slates. 1908. Price, 15 ceuls. '

129. Barium, a Cause of the Loco- Weed Disease. 1908. Price, 10 cents. ^

130. Dry-Land Agriculture. 1908. Price, 10 ceiats.

131. Miscellaneous Papers. 1908. Price, 10 cents. ]

133. Peach, Apricot, and Prune Kernels as By-Products. 1908. Price, 5 cents. '

134. Influence of Soluble Salts, Principally Sodium Chlorid, upon Leaf Structure and Transpiration '

of \Yheat, Oats, and Barley. 1908. Price, 5 cents. '

135. Orchard Fruits in Piedmont and Blue Ridge Regions, etc. 1908. Price. 20 cents. \

136. Methods and Causes of Evolution. 1908. Price, 10 cents. ;
i 137. Seeds and Plants Imported. Inventory No. 14. 1909. Price, 10 cents. '

138. The Production of Cigar-Wrapper Tobacco under Shade. 190.8. Price, IS cents. "*

1.39. American Medicinal Barks. 1909. Price, 15 cents. ■

140. "Spineless" Prickly Pears. 1909. Price, 10 cents. ^

141. Miscellaneous Papers. 1909. Price, 10 cents.

142. Seeds and Plants Imported. Inventory No. 15. f909. Price, 10 cents.

143. Principles and Practical Methods of Curing Tobacco. 1909. Price, 10 cents. '

144. Apple Blotch, a Serious Disease of Southern Orchards. 1909. Price, 15 cents. .«

145. Vcgclation AtYecled bj' Agriculture in Central America. 1909. Price, 15 cents.

140. The Superiority of Line Breeding over Narrow Breeding. 1909. Price, 10 cents. ' i

147. Suppressed and Intensified Characters in Cotton Hybrids. 1909. Price, 5 cents. 'i

14S. Seeds and Plants Imported. Inventory No. Ki. 1909. I'rice, 10 cents. ■■

149. Diseases of Deciduous Forest Trees. 1909. Price, 15 cents. '

1.50. The Wild Alfalfas and Clovers of Siberia. 1909. Price, 10 cents. "^
151. Fruits Recommended for Cultivation. 1909. Price, 15 cents.

1.52. The Loose Smuts of Barley and Wheat. 1909. Price, 15 cents. '

153. Seeds and Plants Imported. Inventory No. 17. 1909. Price, 10 cents. i

1.54. Farm Water Supplies of Minnesota. 1909. Price, 15 cents. t

1.55. The Control of Black-Rot of the Grape. 1909. Price, 15 cents.
1.50. .V Study of Diversity in Egvptian Cotton. 1909. Price, 15 cents.

157. The Truckee-Carson Experiment Farm. 1909. Price, 10 cents. 'i

1.58. The Root-Rot of Tobacco Caused ))y Thielavia Basicola. 1909. Pri<'c, 15 cents. '

1.59. Local Adjustment of Cotton Varieties. 1909. Price, 10 cents.

liiO. Italian Lemons and Their Bv-Products. 1909. Price, 15 cents. - '.
Itil. A New Type of Indian Corn'from China. 1909. Price, 10 cents.

102. Seeds and Plants Imported. Inventorv No. 18. 1909. Price, 10 cents. i

103. Varieties of American Upland Cotton. ' 1910. Price. 25 cents.

104. Promising Root Crops for the South. 1910. Price, 10 cents. ;

105. Applicalionof Some of (he Principles of Heredity to Plant Brecdiim. I'.do. I'rice, 10 cffnts ,
loii. The Mistletoe Pest in the Southwest. 1910. Price, 10 cents. ' '-'
107. New Methods of Plant llreeding. 1910. Price, 20 cents. '.
His. Seeds anti Plants ImiJorted. Inventory No. 19. 1900. Price, 5 cents. '
1(>9. V.T,riega1cd Alfalfa. 1910. Price, 10 cents. ^

170. Traction Plowing. 1910. Price, 10 cents.

171. Some Fungous Diseases of Economic Importance. 1910. Price, .'5 ceuls. '

172. Grape Investigations in N'inifera Regions. 1910. Price. 25 lents. 4

173. Seasonal Nitrification as Influenced by Crops anil Tillage. 1910. Price, 10 eenls.

174. The Conlrol of Peach Brown-Ivot and Scab. 1910. Price, 10 cents. "

175. The History and Distribution of Sorghum. 1910. Price, 10 cents. ;
170. Seeds and Plants Imported. Inventory No. 20. 1910. Price, 5 cents. i

177. .\ I'rotected Slock Range in Arizona. 1910. Price, 15 cents. ;

178. Improvement of the Wheat Crop in California. 1910. Price, 10 cents.

179. The Florida Velvet Bean and Related Plants. 1910. Price, 10 cents. :

180. .'Vgricullural and Botanical E.xplorations in Palestine. 1910. Price, 15 cents. ;
IM. The Curly-Top of Beets. 1910. Price, 16 cents.

182. Ten Years' E.xperience with the Swedish Select Oat. 1910. Price, 10 cents. • '

183. Field Studies of the Crown-Gall of the Grape. 1910. Price. 10 cents.

184. Production of Vegetable Seeds: Sweet Corn ami Garden Peas and Beans. 1910. Price, 10 cents '

185. Cold Resistance of .\lfalfa and Some Factors Influencing It. 1910. Price, — cents.

]8f.. Field Studies of Crown-Gall and Hairy-Root of the .\pple Tree. [In press.] '

187. Study of Cultivation Methods and Crop Rotation for Great Plains Area. [In press.] ]

188. Dry Farming in Relation to Rainfall and Evaporation. [In press.] '

189. Source of Drug Dioscorea, etc. [In press.]

190 •

U. S. DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 191.

B. T. GALLOWAY, Chief of Bureau.

THE VALUE OF FIRST-GENERATION
HYBRIDS IN CORN.

BY

G. N. COLLINS,

Botanist, Crop Acclimatization and Adapta-
tion Investigations.

Issued October 22, 1910.

WASHINGTON;

GOVERNMENT PRINTING OFFICE.
1910.

BULLETINS OF THE BUREAU OF PLANT INDUSTRY. ■

The scientific and technical publications of the Bureau of Plant Industry, which was organized July :

1, 1901, are issued in a single series of bulletins, a list of which follows. i

Attention is directed to the fact that the publications in this series are not for general distribution. The . j
Superintendent of Documents, Government Printing' Office, Washington, D. C, is authorized by law to
sell them at cost, and to him all applications for these bulletins should be made, accompanied by a postal

money order for the required amount or by cash. Numbers omitted from this list can not be furnished :

No. 2. Spermatogenesis and Fecundation of Zamia. 1901. Price, 20 cents. \

' 3. Macaroni Wheats. 1901. Price, 20 cents. :

4. Range Improvement in Arizona. 1901. Price, 10 cents. \

8. A Collection of Fungi Prepared for Distrilnition. 1902. Price, 10 cents. ;

9. The North American Species of Spartina. 1902. Price, 10 cents. ;

10. Records of Seed Distribution, et^. 1902. Price, 10 cents. -^

11. Johnson Grass. 1902. Price, 10 cents. '

13. Range Improvement in Central Texas. 1902. Price. 10 cents.

14. The Decay of Timlier and Methods of Preventing It. 1902. Price, 55 cents. .

15. Forage Conditions on Northern Border of Great Basin. 1902. Priee, 15 cents. •
17. Some Diseases of the Cowpea. 1902. Price, 10 cents. ,-
20. Manufacture of Semolina and Macaroni. 1902. Price, 15 cents. \

22. Injurious Effects of Premature Pollination. 1902. Price, 10 cents. " i

23. Berseem: The Great Forage and Soiling Crop of the Nile Valley. 1902. Price, 15 cents. 1

24. Unfermented Grape Must. 1902. Price, 10 cents.

25. Miscellaneous Papers. 1903. Price, 15 cents. , ;
27. Letters on Agriculture in the West Indies, Spain, and the Orient. 1902. Price, 15 cents.

29. The Effect of Black-Rot on Turnips. 1903. Price, 15 cents.' '

31. Cultivated Forage Crops of the Northwestern States. 1902. Price, 10 cents. \

32. A Disease of the White Ash. 1903. Price, 10 cent^. >j

33. North American Species of Leptochloa. 1903. Price, 15 cents. >
35. Recent Foreign E.xplorations. 1903. Price, 15 cents.

3(i. The "Bluing" of the Western Yellow Pine, etc. 1903. Price, 30 cents.

37. Formation of Spores in Sporangia of Rhizopus Nigricans, etc. 1903. Price, 15 cents. -I

38. Forage Conditions in Eastern Washington, etc. 1903. Price, 15 cents. .i

39. The Propagation of the Easter Lily from Seed. 1903. Price, 10 cents. '

41. The Commercial Grading of Corn. 1903. I'rice, 10 cents.

42. Three New Plant Introductions from Japan. 1903. Price, 10 cents.

47. The Description of Wheat Varieties. 1903. Price, 10 cents. ,

48. The Apple in Cold Storage. 1903. Price, 15 cents. :>.

49. The Culture of the Central American Rubber Tree. 1903. Price, 25 cents. . :
60. Wild Rice: Its Uses and Propagation. 1903. Price, 10 cents.

51. Miscellaneous Papers. 1905. Price, 5 cents. ■

54. Persian Gulf Dates. 1903. Price, 10 cents. ;

59. Pasture, Meadow, and Forage Crops in Nebraska. 1904. Price, 10 cents. ■

60. A Soft Rot of the Calla Lily. 1904. Price, 10 cents. ''

61. The Avocado in Florida. 1904. Price, 5 cents. . •:

62. Notes on Egvptian Agriculture. 1904.- Price, 10 cents. i

67. Range Investigations in Arizona. 1904. Price, 15 cents. •

68. North American .Species of Agrostis. 1905. Price, 10 cents. . \

69. American Varieties of Lettuce. 1904. I'rice, 15 cents.

70. The Commercial Status of Durum Wheat. 1904. Price, 10 cents. "

71. Soil Inoculation for Legumes. 1905. Price, 15 cents. ''^

72. Miscellaneous Papers. 1905. Price, 5 cents.

73. The Development of Single-Germ Beet Seed. 1905. Price, 10 cents.

74. The Prickly Pear and Other Cacti as Food for Stock. 1905. Price, 5 cents. >,

75. Range Management in the State of Washington. 1905. Price, 5 cents.

76. Copper as an Algi<ide and Disinfectant in Water Supplies. 1905. Price, 5 cents. -,

77. The Avocado: A Salad Fruit from the Tropics. 1905. Price, 5 cents. . ■]

79. Variabilitv of Wheat Varieties in Resistance to Toxic Salts. 1905. Price, 5 cents. ;

80. Agriculiufal Explorations in Algeria. 1905. Price, 10 cents. '

81. Evolution of Cellular Structures. 1905. Price, 5 cents. \

82. Grass Lands of the South Alt^ska Coast. 1905. Price, 10 cents. :

83. The Vitality of Buried Seeds. 1905. Price, 5 cents. \

84. The Seed of the Bluegrasses. 1905. Price, 5 cents. ':

85. Principles of Mushroom Growing and Mushroom Spawn Making. 1905. Price, 10 cents. \
80. Agriculture without Irrigation iii the Sahara Desert. 1905. Price, 5 cents. ,

88. Weevil- Resisting Adaptations of the Cotton Plant. 1906. Price, 10 cents. 1

89. Wild Medicinal Plants of the United States. 1906. Price, 5 cents. :

90. Miscellaneous Papers. 1906. Price, 5 cents. * k

91. Varieties of Tobacco Seed Distributed, etc. 1906. Price, 5 cents. ■

94. Farm Practice with Forage Crops in Western Oregon, etc. 1906. Price, 10 cents,

95. A New Type of Red Clover. 1906. Price, 10 cents.

96. Tobacco Breeding. 1907. Price, 15 cents. 1

97. Seeds and Plants Imported. Inventory No. 11. 1907. Price, 15 cents. ,

98. Sov Bean Varieties. 1907. Price, 15 cents. \

99. Quick Method for Determination of Moisture in Grain. 1907. Price, 5 cents. j

101. Contents of and Index to Bulletins Nos. 1 to 100. 1907. Price, 15 cents.

102. Miscellaneous Papers. 1907. Price. 15 cents. , \

103. Dry Farming in the Great Basin. 1907. Price, 10 cents.

104. The Use of Feldspathic Rocks as Fertilizers. 1907. Price, 5 cents. ;

105. Relation of Leaf to Burning Qualities of Tobacco. 1907. Price, 10 cents.

106. Seeds and Plants Imported. Inventory No. 12. 1907. Price, 15 cents. V

(Continued on page 3 of cover.] \

191 ^

U. S. DEPARTMENT OE AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 191.

B. T. GALLOWAY, Chief oj Bureau.

THE VALUE OF FIRST-GENEKATION
HYBRIDS m CORN.

BY

G. N. COLLINS,

Botanist, Crop Acclimatization and Adapta-
tion Investigations.

Issued October 22, 1910.

WASHINCITON;

government printing office.

1910.

BUREAU OF PLANT INDUSTRY.

Chief of Burmu, Beverly T. Galloway.
Assistant Chief of Bureau, G. Harold Powell.
Editor, 3. E. Rockwell.
Chief Clerk, James E. Jones.

Crop Acclimatization and Adaptation Investigations.

SCIENTIFIC staff.

O. F. Cook, Bionomist in Charge.
G. N. Collins, Botanist.
F. L. Lewton, Assistant Botanist.
H. Pittier, Special Field Agent.

E. B. Boykin, J. H. Kinsler, Argyle McLachlan, and D. A. Saunders, Agents.
E. C. Ewing and H. M. Meade, Assistants.
191
2

LETTER OF TRANSMITFAL

U. S. Department of Agriculture,

Bureau of Plant Industry,

Office of the Chief,

Washington, D. C, July 5, 1910.
Sir: I have the honor to transmit herewith a paper entitled ''The
Vahie of First-Generation Hybrids in Corn," by Mr. G. N. Colhns,
a Botanist of this Bureau, and recommend its piibhcation as Bulletin
No. 191 of the Bureau series.

This report shows how the vigor and fertility of hybrids may be
utilized to increase the yield of the corn crop, in addition to other
factors of adaptation and breeding.
Respectfully,

Wm. a. Taylor,

Acting Chief of Bureau.
Hon. James Wilson,

Secretary of Agriculture.

101 o

CONTENTS,

Page.

Introduction 7

Peculiar habits of the corn plant 8

First-generation hybrids confused with hybrid varieties 8

Vigor of hybrids a factor of production 9

Popular belief in the superiority of first-generation hybrids 9

Pre\dous experiments with first-generation hybrids 10

Experiments in Michigan 10

Experiments in Indiana 12

Experiments in Maine 13

Experiments in Illinois 13

Experiments in New York 17

Experiments in Connecticut 18

A new series of hybrids between diverse types 20

Hybrid Ah3, Maryland dent by Hopi 22

Hybrid Ah4, Tuscarora by Cinquantino 22

Hybrid Dhl, Kansas dent by Chinese 23

Hybrid Dh2, Chinese by Chihuahua 23

Hybrid Dh3, Hopi by Chinese 24

Hybrid l)h4, Chinese by Xupha 24

Hybrid Dh6, Brownsville by Chinese 25

Hybrid Ehl, Hopi by Algerian pop 25

Hybrid Gh2, Tom Thumb by Quezaltenango black 25

Hybrid Kh31, Brownsville by Guatemala red 26

Hybrid Kh62, Guatemala red by Salvador black 26

Hybrid Mhl3, Quarentano by Brownsville 27

Hybrid Mhl5, Huamamantla by Hairy Mexican 27

Hybrid MhKi, Arribeiio by Hairy Mexican 28

Hybrid Mhl7, Hairy Mexican by Chinese 28

Hybrid ]\Ih25, Mexican dent by Tom Thumb 28

Yields of first-generation hybrids 28

Extension of corn culture by first-generation hybrids 31

First-generation hybrids and centralized seed production 33

First-generation hybrids in sweet corn 34

Methods for testing corn hybrids 35

Different methods of producing hybrid seed 37

Conclusions 39

Index 41

101 5

B. P. 1.-593.

THE VALUE OF FIRST- GENERATION
HYBRIDS IN CORN.

INTRODUCTION.

The use of first-generation liybrids oflfers one of the most promising
methods of increasing the yield of corn. The evidence that crossing
can in general be relied upon to give an immediate increase of vigor
and productiveness appears conclusive, yet the practice seems never
to have been applied on a commercial scale. The plan of utilizing
first-generation hybrids involves the making of the cross anew each
year, and this is readily feasible with corn. Many efforts have been
made to develop hybrid varieties, but the increased vigor and pro-
ductiveness that result from hybridization appear to be confined
largely to the first generation and to disappear gradually in later
generations.

The present paper reports experiments with a series of first-
generation hybrids between widely different types of corn and brings
together the results of previous experiments. Investigations that
warrant the placing of confidence in this method of increasing the
yields of corn are scattered over a long period of years, and most of
them appear to have been made in ignorance of similar work pre-
viously reported. Individual experiments taken alone have not
made it perfectly clear that the results were not accidental, but the
assembled evidence forces the conclusion that the increases secured
in the first generation by crossing varieties can be made a factor of
production comparable in importance to breeding.

It was indicated more than three decades ago that seed pro-
duced by crossing two varieties of corn could be relied upon to pro-
duce larger crops than the parents, and that this increase was to a
great extent lost in following generations.

At about the tune when it was discovered that an increase in yield
and vigor followed the crossing of two varieties, the attention of
investigators was attracted to the possibility of the improvement of
corn through what then appeared the more scientific methods of
selection. The latter idea was in accord with the most advanced
ideas of evolution, while the former appeared as an isolated fact dis-
covered by accident.

52927°— Bull. 191—10 2 7

8 VALUE OF FIKST-GENEKATION HYBRIDS IN CORN.

It was natural that investigators should follow out what appeared
to be the more logical and scientific method. The fact that yields
could be materially increased by simply crossing two varieties was
lost sight of. Great strides have been made in the knowledge and
possibilities of corn improvement by selection, but until the past-
few years the possibility of utilizing the vigor of first-generation
hybrids of corn has remained almost exactly where it was left by the
pioneer experimenters.

PECULIAR HABITS OF THE CORN PLANT.

Even after the increased vigor of first-generation hybrids became
recognized as a general principle it was not appreciated that the
peculiar habits of the corn plant made its commercial application
to this crop entirely feasible. Corn is peculiar among the important
crop plants in being wind-pollinated and in having the male and
female flowers on widely separated parts of the plant. This com-
bination of characters permits the production of crossed seed in
large quantities by the simple expedient of planting two varieties
together and removing the tassels from the plants of one variety,
which will then produce only hybrid seed. The importance of this
fundamental ditTerence between the flowering habits of corn and
those of other crops has not been sufficiently appreciated. Systems
of breeding developed for other plants have been applied to corn,
diverting attention from this more simple method of im})rovement
made possible by the peculiar habits of the plant. The use of first-
generation hybrids will doubtless be found applicable to other crops,
but in few will its utilization be so easily accomplished as with corn.

FIRST-GENERATION HYBRIDS CONFUSED WITH HYBRID

VARIETIES.

The utilization of crossing as a means of securing increased yields
was further retarded by the failure to realize that the high performance
of the generation immediately following a cross is not maintained in
subsequent generations. Much effort has been expended in attempt-
ing to establish hybritl varieties, overlooking the possibilities of the
direct use of hybrid seed of the first generation. The fact that few
of the hybrid varieties have been found to have permanent value
should not prevent the appreciation of the vigor that immediately
follows the crossing.

Until recently hybrids were usuafly made by hand-pollination and
the quantity of first-generation seed was necessarily small. That
the plants from this seed were especially vigorous and productive
aroused the hope that a happy combination of varieties had been
discovered, and attention was at once centered on the increase of the

191

BELIEF IN SUPEKIOKITY OF FIKST-GENEEATION HYBKIDS. 9

stock and its further improvejiient. In the succeeding generations
diversity appeared and before the desired uniformity could again
be secured through selection the increased vigor resulting from the
crossing had disappeared,

VIGOR OF HYBRIDS A FACTOR OF PRODUCTION.

Comparatively few recent experiments with a direct bearing on
the value of first-generation hybrids have been reported, but all
that have been made confirm the earlier results. Taken in connec-
tion with the experiments to be reported in the present paper they
establish beyond question that the vigor of first-generation corn
hybrids is a means of securing increased production that is capable
of a very wide application. As soon as the general public becomes
acquainted with such a simple and inexpensive means of increasing
the yield of this most important crop, a rapid extension of the
practice should follow. The great need is for detailed information
regarding the particular varietal combinations best adapted to the
different local conditions. At present the data are so meager that
experiments must proceed empirically, but the lack of detailed
information should not obscure the importance of the subject nor
stand in the way of utilizing the results already accomplished.

While it would appear safe to recommend this method to all corn
producers, the object of the present bulletin is rather to urge the
inauguration of experiments in as many parts of the country as
possible. It is much as though the possibilities of increased yields
through the application of commercial fertilizers were still unappre-
ciated by the general public and experiments to prove their efficacy
were being conducted in a few isolated localities. Indeed, the
utilization of first-generation hybrids appears to have more general
application than the use of commercial fertilizers, but the need for
experiments under a wide range of conditions is equally great. As
in the use of fertilizers, conditions may perhaps be found where the
increase from crossing will be slight or none at all, but even this
result should not detract from the fact that under most conditions
the increases are significant.

POPULAR BELIEF IN THE SUPERIORITY OF FIRST-GENERATION

HYBRIDS.

Though the possibility of utilizing the vigOr of first-generation
hybrids is only beginning to be appreciated from the scientific stand-
point, the increased yields that result from crossing have probably
been utilized unconsciously since prehistoric times. It is a regular
custom among many native American tribes to carefully plant seeds
of different varieties in each hill of corn. This is done for the purpose

191

10 VALUE OF FIRST-GENERATION HYBRIDS IN CORN.

of increasing the yield. Though the expected increase is usually
associated in the minds of the natives with superstitious ideas
regarding sexuality in the plants, the vigor secured by such crosses
may well have been an important factor in establishing this custom
with primitive tribes.

The value of first-generation hybrids is further recognized in a
widespread belief among practical seed growers that the plants
produced by accidental crosses of pure strains are often exceptionally
vigorous. The following statement from Dr. W. W. Tracy, who
has had a wide experience in the practical breeding of plants and in
commercial seed production, voices this belief:

The. second step is the selection of a few plants which shall come as near to the ideal
as possible and the saving of the seed of each of these separately. I recommend this
instead of selecting the best one because it often happens that the very best plant is in
reality a crossed one which owes its superiority to a cross of some exceptionally vigor-
ous but otherwise inferior plant, and this "bar sinister " will be revealed in the inferior
quality of plants grown from its seed.o

PREVIOUS EXPERIMENTS WITH FIRST-GENERATION HYBRIDS.

EXPERIMENTS IN MICHIGAN.

That the immediate result of crossing two varieties is to increase
the jneld was shown by definite experiments as early as 1878 by
Dr. W. J. Beal, of the Michigan Agricultural Experiment Station.
The plan for such experiments had been outlined two years before,
in 1876, the same year that Darwin published his classical work on
self and cross fertilization in plants, but without knowledge of
Darwin's results. Doctor Beal's first statement was as follows:

To improve or infuse new vigor into varieties (or races I should more properly call
them) I propose in case of corn and some other seeds to get seeds from remote parts
where it has been grown for some years, and plant near each other and mix theni.&

Even at this early date Doctor Beal appreciated the fact that the
benefits were largely confined to the first generation.

The good results of such crossing will last for several years, though most apparent
the first year.c

The nature of the first experiment and its relation to the similar
experiments of Darwin are shown in the following quotation:

From several different sources in remote parts of our State I obtained white dent corn
and yellow dent corn for seed. So far as possible I obtained good seed from men who
had raised the corn for ten or more years in succession on the same farm.

a Tracy, W. W. Importance of Uniformity of Varietal Character in Vegetable
Seeds. Market Growers' Journal, October 30, 1909, p. 2.

6 Beal, W. J. Report, Michigan Board of Agriculture, 1876, p. 206.
c Loc. cit.
191

PREVIOUS EXPERIMENTS WITH FIRST-GENERATION HYBRIDS. 11

I crossed some white dent from one locality with pollen from white dent obtained in
a remote locality. This may add vigor to the race, though it will probably not other-
wise change the race. The plan was conceived by me about a year ago, and several
months afterwards the same kind of experiments were reported on many species of
plants by Mr. Charles Darwin, of England. The favorable results of many experiments
there given are quite remarkable. «

In 1880 the representatives of five dift'erent agricultural schools
entered into an agreement to test by a uniform experiment at their
several stations this method of corn improvement. Each experi-
menter was to report his experiment to the other parties to the
agreement.

The details of this agreement are given as follows:

Each man in his own State shall select two lots of seed corn which are essentially
alike in all respects. One should have been grown at least for five years (better ten
years or more) in one neighborhood and the other in another neighborhood about 100
miles distant. In alternate rows plant the kernels taken from one or two ears of each
lot. Before plowing, thin out all poor or inferior stalks. As soon as the tassels begin
to show themselves in all the rows of one lot, pull them out, that all the kernels on the
ears of those rows may certainly be crossed by pollen from the other rows. Save seed
thus crossed to plant the next year by the side of seeds of each parent. Seeds of one
parent can be obtained from the rows not topped. Seeds of the other parent should be
planted by themselves to get pure seeds of the same year.

For the second year, select two pieces of ground, each as even as possible, about 4
by 8 rods in extent. Manure it evenly as possible with barnyard manure if any fer-
tilizer is employed. Plow the ground without bed or ridge furrows or, if either occur,
plant so that a row of each comes at equal distance from the ridge or bed furrow.
Take no unusual pains to make the ground very rich or to cultivate better than usual.
Keep the cultivation alike on all parts of the plats as nearly as possible.

On one of these plats plant some of the cross seeds in alternate rows with seeds of one
of the parents. On the other plat plant the crossed seeds in alternate rows with the
other parent. Seeds of each parent raised the previous year will thus be tested with
seeds of the same age from the cross. Take notes of the time in which the plants in
each row come up and of the appearance from time to time. Make plats of the corn
and be careful to keep everything straight. Take notes of the time of maturing, and
when matured cut near the ground the hills of each row and shock separately. After
it is cured, husk and weigh the ears and the stalks separately of each row. It would
be well to weigh the dried shell corn of each row separately. In the report give the
weight of corn and stalks of each row separately, then a summary of the weights of each
parent and the crossed stalk. Each experimenter shall report his experiments thus
made to each of the other persons entering into this arrangement.

A similar experiment was made at the agricultural college in 1878. In this the
advantage shown by crossing of corn over that not crossed was as 151 exceeds 100, and
in the case of black wax beans it was as 236 exceeds 100. In a similar experiment
made during the past two years at the agricultural college, the corn from seed of
crossed stock exceeded that not so crossed as 109fVV exceeds 100, or nearly 10 per cent
in favor of crossed stock. The experiment was quite carefully made and I do not
consider this result as purely accidental. ^

« Beal, W. J. Report, Michigan Board of Agriculture, 1877, p. 56.
b Ibid., 1880, pp. 287-288.
I'Jl

12 VALUE OP FIEST-GENEEATION HYBRIDS IN COKN.

After a lapse of more than thirty years it is hardly possible to
improve or refine the method of experimentation as outlined by this
pioneer. His method of comparing yields by alternate-row plantings
was also more perfect than that of his successors and is again coming
into use as the best that has yet been devised.

In 1881 Doctor Beal made another cross, between two varieties
from Oakland and Allegan counties, respectively, and reported the
results of the cross as follows :

The Oakland County seed corn was the better of the two. Owing to an accident
we failed to raise any pure Allegan County seed in 1881. The "crossed corn" was only
compared with pure Oakland County seed raised last year at the college.

In the spring of 1882, on good soil in a portion of the vegetable garden, three rows of
"crossed seed " were planted in rows alternating with three other rows of pure Oakland
County seed of 1881. By an oversight each row af each lot was not kept separate.
The pure seed yielded 57] pounds in the ear; the "crossed seed" yielded 69J pounds
in the ear. In other words, the crossed stock exceeded the pure stock as 121 exceeds
100, nearly."

EXPERIMENTS IN INDIANA.

Of the five cooperators entering into the agreement with Doctor
Beal to test first-generation hybrids. Prof. C. L. Ingersoll, of Purdue
University, seems to have been the only one who reportetl results.
In this case it appears that seed of the variety detasseled was not saved,
so that the hybrid was compared with only the male parent. Since
in this case the cross was made between two strains of the same
variety, this failure does not entirely vitiate the results. The experi-
ment is reported as follows:

I took corn from Delaware County and also from Switzerland County, in this State,
and planted as in first year's directions.

The tassels were removed from the Delaware County corn, so that it was certainly
fertilized by pollen from the Switzerland County corn. Both were a white dent
variety. The result of corn raised was as follows:

Delaware County (hybrids), 122 pounds, 27.89 bushels per acre.

Switzerland County, 63 pounds, 14.40 bushels per acre.

Switzerland County (alone), 72 pounds, 16.46 bushels per acre.

These results, although small, seem to show that in this instance at least, and with
the experiment half completed, there is a marked difference in cross-fertilized and
self-fertilized corn when the seed from the crossing is obtained from widely sepa-
rated localities and is of the same variety .&

It seems that the experiment was again attempted two years later''
and hybrid seed was secured, but subsequent reports of the university
do not show that the experiment was ever completed, Professor
Ingersoll having left the institution.

oBeal, W. J. Report, Michigan Board of Agriculture, 1881-2, p. 136.
ft Seventh Annual Report of Purdue University for 1881, p. 87.
c Ninth Annual Report of Purdue University for 1883, p. 72.
191

PREVIOUS EXPEKIMEKTS WITH FlEST-GENERATION HYBRIDS. 13
EXPERIMENTS IN MAINE.

The only reference by subsequent workers to Doctor Beal's experi-
ments so far as we have ascertained is that of Prof. J. W. Sanborn in
reporting a similar experiment in ]\Iaine.

Professor Beal found that outcrossed corn, as the average of two years of trial, gave
as 1:51 is to 100 for inbred corn. I found the same result, or as 252 is to 179, and
for fodder as 490 is to 350. The facts have a deep significance to our farmers."

EXPERIMENTS IN ILLINOIS.

Nine years after the work of Doctor Beal and apparently in ignor-
ance of his results, Mr. G. W. McCluer reported the results of a series
of crosses made at the Illinois Agricultural Experiment Station. He
did not give actual yields, but noted the average size of the ear as
compared with that of the parents in 18 crosses comprising 14 differ-
ent combinations of dent, pop, soft, and sweet corn. In 16 of the 18
crosses, or 12 of the 14 different combinations (2 were duplicates and
2 reciprocals), the ears of the first-generation hybrid were larger than
an average of the parents, and in 4 of the crosses the hybrid ears
were larger than those of either parent. One of the exceptions is
stated to have been planted in an unfavorable location. The decrease
in the other case was 4.6 per cent. The average increase in weight
for the whole series was 14 per cent.

With respect to the uniformity of the first-generation hybrids,
McCluer says:

During the first growing season the uniformity of the crossed plats was very notice-
able. Of 142 plats planted with sweet corn, pop corn, and these crosses it is safe to
say there was as much uniformity in any one of the crossed plats as in any, and very
much more than was found in most, of the plats planted with pure varieties. &

The following year, 1891, a number of the ears from this crossbred
corn were again planted and Mr. ]\IcCluer says:

Nearly all the corn grown a second year from the crosses is smaller than that grown
the first year, though most of it is yet larger than the average size of the parent varie-
ties. The cause of this apparent decrease in size, as compared with the previous
year, can only be guessed at. It can not be attributed to the season, because the
Queen's Golden-Common Pearl pop corn and Gold Coin-Flour corn crosses grown
in 1891 show as large a proportionate increase in size of ear as is shown in any
of the crosses grown in 1890. There is probably a strong natural tendency in the
crosses to revert to the size as well as the form of the parent types. This is shown in
the Leaming sweet-corn crosses, in which the corn reverting to the dent is larger
than that reverting to the sweet types. Or the loss of size may be due to a diminu-
tion in some way of the vigor imparted by crossing."

"Sanborn, J. W. Indian Corn. Agriculture of Maine, Thirty-Third Annual Re-
port, Maine Board of Agriculture, 1889-90, p. 78.

6 McCluer, G. W. Corn ('rossing. Bulletin 21, Illinois Agricultural Experiment
Station, 1892, p. 85.

cOp. cit., p. 96.
191

14

VALUE OF FIRST-GENERATION HYBRIDS IN CORN.

In view of the interest that attaches to these early experiments,
Mr. McCluer's tabuLated results are o;iven as follows:

Table I. — Results of Mr. G. W. McCluer's experiments with corn hybrids at the Illinois
Agricultural Experiment Station, showing the effect on the size of ear.

Cross.

—
s

OI

i-'C
o ^

o

o

o >

°S
■«^
Th

'53

O
C3-3

•si

n

-=1

a

Weight of 10 ears the second year after the
cross, ounces.

White dent— Queen's Golden 81

34.5

57.75

76

Ears like the dent type 64

Ears like the pop corn type 52.5

Queen's Golden— White dent 34. 5

81

57.75

64

Ears like flint corn 55

Ears like pop corn type 47.5

Black Mexican— Queen's Golden....

36

34.5

35.25

47.5

Types not separated 43. 5

Queen's Golden— Common Pearl
pop corn.

34.5

27.5

31

42

Not grown a second year.

Learning — Mammoth . ...

87.5

61.5

74.5

91

Corn grown from yellow dent kernels 86
Corn from white dent kernels 90

Corn from sweet kernels 74

LeaminsT — Mammoth

87.5

61.5

74.5

82

Not grown a second year.

Learning — Maminolh

87.5

6L5

74.5

80.5

Not grown a second year.

Leamin^ — TriuiriDh

87.5

46.5

67

83

Corn from dent kernels 86

Corn from sweet kernels 68

Learning — Eight-rowed

87.5

41

64.25

72

Corn from white dent kernels 80

Corn from yellow dent kernels 75

Corn from sweet kernels 58

Gold Coin — Flour corn

63

39

51

78

Has not yet been grown a second year.

" "

Black Mexican— White dent

36

81

58.5

51

From flint kernels of flinty ears 53

From flint kernels of sweet ears 40

From sweet kernels of flint ears 39

From sweet kernels of sweet ears .-. . 38. 25

Stowell's — Eight-rowed

57. 5

41

49.25

47

From selected ears 49

From self-fertilized ears 38

From cross-fertilized ears 43

Stowell's — Triumph

57.5

46.5

52

52.5

From self-fertilized seed 31

From cross-fertilized ear 48. 5

Do 41

Seed from selected ears 54

Seed from self-fertilized ears 39

Stowell's — Mammoth

57.5

61.5

59.5

61

Self-fertilized ear, plat 88 43

Self-fertiUzed ear, plat 76 52

From cross-fertilized ear, plat 86 — 55

From cross-fertilized ear, plat 87 45. 5

Seed from selected ears 55

Stowell's— Gold Coin

57.5

62.5

60

62.5

From self-fertilized ear, plat 89 48

From self-fertilized ear, plat 90 54

From self-fertilized ear, plat 91 54

Seed from selected ears 58

Seed from self-fertilized ear 48

Gold Coin — Triumph

62.5

46.5

54.5

58.5

From cross-fertilized ear, plat 93 — 56
From cross-fertilized ear, plat 92 50

Seed from selected ears 49

Gold Coin — Eight-rowed

62.5

41

51.75

56

Seed from selected ears 50

Gold Coin — Eight-rowed

62.5

41

51.75

58

Not grown a second year.

191

PREVIOUS EXPEEIMENTS WITH FIRST-GENEEATION HYBRIDS. 15

The table further shows the marked decrease in size of ear in the
hybrids that follows even one generation of self-fertilization. There
is, however, so much ''splitting" in the type of the ears in the second
year that their size, as compared with those of the second generation,
can not fairly be expressed in averages.

The following year, 1892, Morrow and Gardner, also at the Illinois
station, reported the results of tests of five first-generation hybrids
compared with their parent varieties." In all cases the yield of the
cross was greater than an average of the parents and in three cases it
exceeded that of either parent. Stated in bushels, the increases
above the average of the parents ranged from 1.2 bushels, or 1.9 per
cent, to 17.2 bushels, or 28 per cent, the average increase being 13.8
per cent. The average increase of the crosses over the highest yield-
ing parents was 4.66 bushels per acre, or 6.5 + per cent. The com-
parisons were apparently made in jL.acre plats. The results of the
experiment are shown in Table II.

Table II.— Results of experiments by Morrow and Gardner xviih corn hybrids at the Illinois
Agricultural Experiment Station in 1892.

Variety.

Burr's White

Cranberry

Average

Cross

Burr's White

Helm's Improved

Average

Cross

Learning

Golden Beauty

Average

Cross

Champion White Pearl
Leaming

Average

Cross

Burr's White

Edmonds

Average

Cross

Yield per acre.

Number
of ears.

9.960
9,200

9,580
7,080

9,960
10,880

Air-dry
corn.

Bushels.
64.2
61.6

62.9
64.1

64.2
79.2

10, 420
11,000

10.440

8,280

9,360
11,520

11,080
10,440

10, 760
8,760

9,960
9,040

9.500
10,400

71.7
73.1

73.6
65.1

69.3
86.2

60.6
73.6

67.1
76.2

64.2
58.4

61.3
78.5

It will be noted that the crosses in this experiment were all between
good-yielding varieties and apparently under favorable conditions.
The relatively uniform results also indicate a small experimental error.

a Morrow, G. E., and Gardner, F. D. Field Experiments with Com, 1892. Bulletin
25, Illinois Agricultural Experiment Station, 1893, pp. 179-180.
52927°— Bull. 191—10 3

16

VALUE OF PIEST-GENERATION HYBRIDS IN CORN.

In the bulletin mentioned the practical possibilities of this method
of increasing yields were indicated, as follows:

The fact that increased yields can be obtained by crossing two varieties is pretty
certainly established, and a few farmers are changing their practice accordingly. This
is quite e^-sily done by planting in one row one variety and in the next another variety,
and removing the tassels of the one as soon as they appear. The ears forming on the
rows having the tassels removed will be fertilized with pollen from the other rows, thus
producing a direct cross between the two varieties. The seed should be selected from
the rows having the tassels removed, and the experiments indicate that it will pretty
certainly give a larger yield than the average of the parent varieties when planted
under like conditions. ^

The above quotation indicates that the authors considered the prin-
ciple as established and worthy of practical application. No expla-
nation has been offered why the matter was again allowed to rest at
this pomt, but so far as can be learned no one has since practiced the
growing of first-generation hybrids on a commercial scale.

In 1893 four additional crosses were planted, three of the four giving
increases over the average of the parents, the average increase being
9.5 bushels, or 7.7 per cent. The results are shown in Table III.^

Table III. — Results of experiments by Morrow and Gardner with corn hybrids at the Illi-
nois Agricultural Experiment Station in 1893.

Variety.

Yield per acre.

Number
of ears.

Air-dry
corn.

Champion White Pearl

Burr's White

Average

Champion White Pearl — Burr's White Cross

Leaming (average 4 plats)

Burr's White

Average

Leaming— Burr's White Cross

Edmonds

Murdock (average 4 plats)

Average

Edmonds — Murdoclc Cross

Edmonds

Burr's White

Average

Edmonds— Burr's White Cross

Bushels.

7.680
10,200

37.3
38.6

8,940
7,080

38
28.4

8,070
10,200

34.6
38.6

9, 1.35
9,480

36.6
41,7

7,740
9.600

28.3
35.7

8.670
9,840

32
41.4

7,740
10,200

28.3
38.6

8,970
9,360

33.5

37.8

The fluctuations in the yields of the different varieties and crosses
in this experiment are so wide that little confidence can be placed in

o Morrow, G. E., and Gardner, F. D., loc. cit.
b Morrow, G. E., and Gardner, F. D. Experiments with Corn.
Agricultural Experiment Station, pp. 359-360.
191

Bulletin 31, Illinois

PREVIOUS EXPERIMENTS WITH FIRST-GENERATION HYBRIDS. 17 i

results. The omission of single members from the series would '

materially change the average. The lack of uniformity in the condi- i
tions is indicated by the great disparity between the yields of duplicate

varieties in this experiment, which ranged as high as 15 bushels per i

acre.'^ i

EXPERIMENTS IN NEW YORK.

After a further lapse of fifteen years, the subject was again '
approached from a somewhat different direction by Dr. G. H. Shull
of the Carnegie Biological Laboratory at Cold Spring Harbor, N. Y.
In his first paper he suggests the possible use of first-generation '
hybrids in the following statement:

The problem of getting the seed corn that shall produce the record crop, or which '

shall have any specific desirable characteristic combined with the greatest vigor, may
possibly find a solution, at least in certain cases, similar to that reached by Mr. Q. I.
Simpson in the breeding of hogs by the combination of two strains which are only at
the highest quality in the first generation, thus making it necessary to go back each '

year to the original combination, instead of selecting from among the hybrid offspring
the stock for continued breeding. 6

The following year Doctor Shull stated his views in greater detail
and reported on the result of crossing two closely related strains. <^
Before these results can be properly appreciated it will be necessary \
to briefly consider the problem from Slmll's standpoint. It is con- '

sidered that even the most nearly uniform varieties of corn consist of
numerous strains, ''elementary species" or ''biotypes," all more or
less mixed and hybridized. To this miscellaneous hybridizing I

Doctor Shull attributes the vigor and fertility of a variety. The >

method he suggests for the improvement of corn is to isolate the j

different strains and by making predetermined combinations to
ascertain which mil be the most favorable for agricultural purposes.
It is fully recognized that isolating the pure strains or biotypes will
very greatly reduce their vigor and yield, but by making a combina-
tion of the proper strains it is believed that the degree of fertility of i
the cross will reach that of the most productive plants in the original i
mixed strain and that an increase of the total yield can be obtained i
in this way. :

Two self-fertilized strains which were separated from a common
stock in 1904 and continuously self-fertilized since that time were i

reciprocally crossed in 1907. In 1908 the yields of these reciprocal
crosses were compared with each other, with the self-fertilized parents,

a Morrow, G. E., and Gardner, F. D., op. cit., p. 338.

b Shull, G. H. The Composition of a Field of Corn. Report, American Breeders'
Association, vol. 4, 1908, p. 300. '

c Shull, G.H. A Pure Line Method in Corn Breeding. Report, American Breeders' i

Association, vol. 5, 1909, p. 51.
191

18 VALUE OF FIKST-GENEEATION HYBRIDS IN CORN.

and with crossbred stocks of the original variety. Reduced to bushels
per acre and placed in tabular form, the yields reported by Shull were
as follows:

Strain A, eelf-fertilized 23. 5 bushels.

Strain B, eelf-fertilized 25. bushels (estimated).

AXB 74. 4 bushels.

BX A 78. 6 bushels.

General average of crossbred stock 75. bushels.

From Doctor Shull's standpoint the important point in the above
comparison is the increase of 1.5 bushels per acre which the average
of the crossed pure strains shows over the average of the cross-pollinated
original stock, an increase of 2 per cent.

At the same time a comparison was also made between the yield of
self and cross pollinated ears of the same isolated strain. The yield
from the cross-pollinated seed was 30 per cent greater than that from
the self-pollinated ear. As an instance of the increased vigor of the
first-generation hybrid this example is of interest, since it indicates
that an increase in yield follows the crossing of even the most closely
related plants.

To many producers of corn it will appear hardly practicable to
apply this system on a commercial scale. Neither does it appear
reasonable on theoretical grounds to look on these anomalous self-
fertilized strains as representing the natural condition. It would
seem that even the most advantageous combinations might be found
without reducing the varieties to the verge of extinction before the
cross is made.

But no method of investigation should be rejected for purely theo-
retical reasons. Until other experimental data are available the
effect of previous breeding upon the vigor of the hybrids must remain
an open question. The importance of the subject demands that all
the phases shall be considered, and those who hold to the conception
of "bio types" and ''pure germ cells" will do well to experiment
along the lines suggested by Doctor Shull.

EXPERIMENTS IN CONNECTICUT.

A more extensive series of crosses was made by Dr. E. M. East at
the Connecticut Agricultural Experiment Station. His results are
stated as follows:

The Fi generation of 30 maize crosses were grown in 1908 on well fertilized land in
Connecticut. They were planted 3 feet 6 inches each way, about foiu- stalks to the
hill. Seeds from the same parent earso which were used to make the crosses were
also grown for comparison. Only 50 hills of each of the crosses and of each parent
could be grown on account of limited space, but the soil conditions were such that a

a "The parent ears were, therefore, one year older, but their germination was good,
and their growth equal to inbred seed of the same ages as the hybrid seed."
191

PREVIOUS EXPERIMENTS WITH FIRST-GENERATION HYBRIDS. 19

very fair indication of the comparative vigor of each strain was obtained. Unfor-
tunately crows and chipmunks played havoc with the "stand " in a number of cases,
and accurate figures can not be given except in the following four cases where the
stand was perfect.

A white dent, No. 8, yielded 121 bushels per acre (at 70 pounds per bushel); a
yellow dent, No. 7, which had been inbred artificially for three years, yielded 62
bushels per acre; the cross between the two varieties, No. 7 X No. 8, yielded 142
bushels per acre.

Longfellow, No. 34, an 8-rowed, yellow flint, yielding 72 bushels per acre, was
crossed with the same No. 8 white dent, yielding 121 bushels per acre; the resulting
cross yielded 124 bushels per acre.

Sturges's hybrid, a 12-rowed, yellow flint with a tall, nonbranching stalk, partaking
of the characters of dent varieties, was also crossed with No. 8 white dent. The flint
parent yielded 48 bushels per acre, while the cross yielded 130 bushels per acre.

Two families of a yellow dent variety, which had each been inbred artificially for
three years, were the parents of the fourth cross. No. 12, yielding 65 bushels per
acre, was crossed with No. 7, yielding 62 bushels per acre. The Fj generation yielded
202 bushels per acre. This last result is somewhat distorted, as five stalks per hill of
the cross were allowed to grow, while of the parents only four seeds per hill were planted.
About 90 per cent of the seeds produced mature stalks. Notwithstanding the close-
ness of planting to which this cross was subjected, however, casual observation was
sufficient to show that it soared far beyond each parent in vigor of plant and size of ear .a

For ease in comparison Doctor East's results are here given in
tabular form:

White dent X yellow dent.
Yellow dent X white dent.
Yellow flint X white dent.
Yellow dent X yellow dent

Yield of
female
parent.

Bushels.

121

72

48

65

Yield of

male
parent.

Bushels.

62
121
121

62

Average
yield of
parents.

Bushels.
91.5
96.5
84.5
63.5

Yield of
hybrid.

Bushels.

142

124

130

*161

Percentage
of increase

over

average of

parents.

Per cent.

55

28.

54

154

* This is the cross of which Doctor East states that five stalks per hill were allowed to grow instead of
four, as in the case of the parents. The yield is here reduced by one-fifth from the original figure of 202
bushels to allow for the additional number of hybrid plants that were grown, although by this calcula-
tion the hybrid is placed at a disadvantage, due to the closeness of the planting.

It will be noted that the comparison with the parents was in this
case very accurate, the plants representing the parents being grown
from the identical ears that were used to make the crosses. The
yield of one of the parents in the first cross and both the parents in
the fourth had, how^ever, been depressed by self-fertilization for three
successive years. It is interesting to note in this connection that the
introduction into a cross of an inbred strain yielding only one-half
that of the other variety here results in increasing the yield above
that of the high-yielding parent by over 17 per cent. Furthermore,
the highest yield in the experiment was secured from a cross between

«East, E. M. The Distinction between Development and Heredity in Inbreeding.
The American Naturalist, vol. 43, no. 507, 1909, pp. 178-179.
191

20 VALUE OF FIRST-GENERATION HYBRIDS IN CORN.

two inbred strains which without crossing were among those which
gave the lowest yields of any represented in the experiment.
Regarding other crosses, Doctor East states:

In the remainder of the field every possible combination of dent, flint, and sweet
maize was grown, and in every case an increase in vigor over the parents was shown
by the crosses. It is to be regretted that comparable yields could not be obtained
in every instance, but, as a matter of fact, the differences were so apparent to the
eye that it is almost unnecessary. The figures presented do not show the average
increase to be expected by a cross. The manuring was heavy, the cultivation inten-
sive, and the yields were beyond the ordinary. But they do show that in practically
every case a combination of two high-bred varieties, of seed corn is more vigorous
than either parent. a

A NEW SERIES OF HYBRIDS BETWEEN DIVERSE TYPES.

The crosses thus far considered have in all cases been between
strains that are comparatively closely related. The most violent
crosses are among those reported by McChier where varieties of
sweet and dent, pop and dent, and sweet and pop corns were included.
The diversity between these types may seem considerable, represent-
ing as they do the extremes of the types now cultivated in the United
States, but looked at botanically these varieties appear closely
related when compared with the very diverse types that exist in the
Tropics.

Over the whole of the United States the interchange of seed has
been so extensive and the culture is so nearly continuous that all
characters are to a great extent shared by the whole series of varie-
ties, even the most divergent types being distinguished by charac-
ters that differ in degree rather than in kind. Even before the advent
of the white man the nomadic tendencies of the North American
Indians must have operated against any complete isolation of types.

The sedentary habits of the Indians of tropical America are in
strong contrast with those of the more northern tribes, and together
with the great diversity of natural conditions have operated to
produce an enormous number of very distinct types, showing numer-
ous specialized adaptations to different conditions, the agricultural
significance of which is only beginning to be appreciated.

As an instance of one of these divergent groups there may be men-
tioned a type of corn cultivated in parts of the lower plateau of
Mexico in a region that receives such scanty rainfall that similar
regions in this country would be thought entirely unsuited for corn
growing. This corn is so different from the types with which we are
familiar that it was given specific rank by Bonafous and named
Zea Jiirta} The leaf sheaths are densely covered with long hairs

oOp. cit., pp. 179-180.

& Bonafous, M. Annales des Sciences Naturelles, vol. 17, 1829, p. 156.
191

A NEW SERIES OF HYBEIDS BETWEEN DIVERSE TYPES. 21

borne on tubercles, the leaves are few and very long and slender,
the tassel is frequently unbranched, the spikelets are in groups of
four or more instead of two, and the clusters are opposite each other
instead of alternate. Even the root system is distinct from that of
any of the common varieties of the United States, being spread out
near the surface of the ground where the only available water is to
be secured in the regions where this type is native. Many varieties
inside this type differ among themselves much as the classes of flint,
dent, and pop corns differ from each other. In fact, a closely similar
series exists in this tropical type, there being varieties which judged
by the ears, would be classed as flint and others as pop and dent corns.

Wliile this type is one of the most distinct, many other tropical
forms possess characters and habits that are entirely absent or only
faintly indicated in United States varieties. Peculiarities of other
tropical types will be, mentioned in connection with the different
crosses that are about to be described.

With a view to securing types adapted to sections of the country
where United States varieties are unsuccessful, a considerable series
of tropical types and varieties has been brought together. In the
season of 1908 about 75 crosses were made among these tropical
varieties, and also between them and several United States varieties.
A number of these hybrids were grown in the summer of 1909 at
Lanham, Md., a few miles from Washington, D. C. The parent
varieties of 16 of these crosses were included in the plat and their
behavior noted in comparison with the crosses. The experiment
was considered as merely preliminary and but 16 hills of each
variety were grown. Wliile this number is altogether too small to be
conclusive as a comparison of the values of the different crosses,
the results as a whole are very significant as an illustration of the
general value of first-generation hybrids. It becomes evident that
the increase in vigor that earlier experiments have proved to be the
rule with crosses of more or less closely related strains has also a very
wide application among even the most primitive, unselected, and
diverse types of corn. In 14 of the 16 crosses the yield exceeded
the average of the parents. In 12 cases it exceeded the yield of either
parent, the average increase for the whole series being about 53 per
cent.

In the following brief account of the hybrids and their parents,
the descriptions will for the most part be confined to the usually
recorded characters of height, yield, and character of the ear, which
data are sufficient to make the results of this experiment comparable
with those previously reported. Detailed observations of the behavior
of the parental characters in these and other hybrid combinations
have been made, but are not needed for the purpose of this report.

191

22 VALUE OF FIKST-GENERATION HYBRIDS IN CORN.

Abnormalities will be briefly noted as a possible indication of the
violence of the cross.

HYBRID AH 3, MARYLAND DENT BY HOPI.

Female parent. — An imselected white dent grown in Maryland.
The particular plant used as the female parent was grown from the
seed of a red ear. This proved to be the most prolific of the uncrossed
strains; perhaps on account of its being the only locally grown variety
in the experiment. No abnormalities were discovered in any part
of the plant or in the* ears. Average height, 6 feet 10 inches. The
16 plants grown produced 21 ears and 2 nubbins, weighing 19
pounds.

Male parent. — A variety grown by the Hopi Indians of Arizona-
The most striking characteristics of the type are the very large male
spikelets and enormous ear stalks. The color of the particular ear
used in making the cross was a slatv blue. No abnormalities
appeared in the plants grown in this experiment, though in Kansas
this strain produced a number of ears with inverted grains, the
embryo on the lower side, toward the base of the ear, and also a
number of grains with double germs. Average height, 8 feet 10
inches. The 27 plants grown produced 21 ears and 2 nubbins, weigh-
ing 20 pounds.

Hybrid. — In spite of the fact that both of the parents yield pollen
very abundantly, 6 of the 16 h3^brid plants failed to produce pollen.
No other abnormalities were observed. The plants were rather
diverse, some resembling one parent and some the other. The ears,
however, were as imiform as those of either parent and partook of
the characters of both. Average height, 7 feet. The 16 plants
grown produced 21 ears and 2 nubbins, weighing 20.1 pounds."

HYBRID AH 4, TUSCARORA BY CINQUANTINO.

Female parent. — An 8-rowed soft variety, grown by the Tuscarora
Indians of New York. The variety is early and suckers profusely,
many of the suckers terminating in ears. Average height, 5 feet 8
inches. The 16 plants grown produced 14 ears and 10 nubbins,
weighing 8.5 pounds.

Male parent. — A variety imported from Hungary under the name
Pignoletto. A very small seeded, many-rowed type that would be
classed as a pop, though unlike any of the American varieties of pop
corn. This class of corn is known to the trade as "Cinquantino."
The variety is small, without suckers, and very early. No abnor-

o The yields of the hybrids and the parent varieties, reduced to pounds per plant,
are brought together for comparison in Table IV, p. 29.
191

A NEW SERIES OP HYBEIDS BETWEEN DIVERSE TYPES. 23

malities. Average height, 4 feet 4 inches. The 14 plants grown
produced 14 ears and 1 nubbin, weighing 3.3 pounds.

Hybrid. — Plants and ears intermediate. No abnormalities.
Average height, 6 feet 7 inches. The 15 plants grown produced 21
ears and 14 nubbins, weighing 11.3 pounds.

HYBRID DH 1, KANSAS DENT BY CHINESE.

Female iMrent. — A white dent developed by Mr. Elam Bartholo-
mew, of Stockton, Kans. The variety has never been closely bred,
but has been grown continuously^ for a number of years and kept up
by selection of ears. No abnormalities. Average height, 7 feet 11
inches. The 29 plants grown produced 26 ears and 4 nubbins^
weighing 28.6 pounds.

Male 'parent. — A vari^y of corn from China, \vith wa^xy endo-
sperm, leaf blades borne on one side of the stalk, and silks pro-
duced in the angle of the leaf blades.**

The parent plant was grown from white seed separated from the
imported mixture and had the erect monostichous leaf blades that
characterize this variety. The second-year plants fi'om American-
grown seed showed these characteristics in a much less marked
degree than those grown from imported seed. No abnormalities.
Average height, 4 feet 7 inches. The 32 plants grown produced 46
ears and 9 nubbins, weighing 12.4 pounds.

Hybrid. — In the early stages the plants resembled the Chinese
parent in having erect monostichous leaf blades, but this character
was less marked later in the season. The plants remained dark green
during a very dry season. The only indication of abnormality was
the frequent production of pistillate flowers on the terminal inflor-
escences of the suckers. The ears were intermediate in size and
appearance and as uniform as those of either parent. Average height,
6 feet 9 inches. The 16 plants grown produced 27 ears and 7 nub-
bins, weighing 17.5 pounds.

HYBRID DH 2, CHINESE BY CHIHUAHUA.

Female parent. — The same as the male parent of hybrid Dhl.

Male parent. — A starch variety from Chihuahua, Mexico. This
variety is peculiar in having the longest leaf sheath at the top of the
plant and in having the leaf sheaths covered with fine velvety hairs.
No abnormalities. Average height, 8 feet 9 inches. The 14 plants
grown produced 13 ears and 2 nubbins, weighing 9.7 pounds.

o This variety ia more fully described in Bulletin 161 of the Bureau of Plant Indus-
try, U. S. Dept. of Agriculture, 1909, entitled "A New Type of Indian Corn from
China."
191

24 VALUE OF FIKST-GENEKATION HYBRIDS IN CORN.

Ilyhrid. — The plants of this cross exhibited greater diversity than
was shown in any other cross. Two of the plants "were so' exactly
like the female parent, both in plant and ear characters, as to arouse
the suspicion that the precautions against foreign pollination had
been imperfect and that the particular grains producing these plants
were self-pollinated. This appears the more probable from the
nature of the Chinese plants, which makes it especially difficult to
exclude pollen from the tips of the silks that appear directly in the
angles of the leaf blades. Wliile the plants showed the complete range
of the parental characters, the ears, with the exception of those
noted above, were fairly uniform. One interrupted ear was pro-
duced; that is, a portion of the ear near the middle produced only
staminate instead of pistillate flowers. Average height, 8 feet 3
inches. The 16 plants grown produced 25 ears and 18 nubbins,
weighing 15.25 pounds.

HYBRID DH 3, HOPI BY CHINESE.

Female imrent. — A plant from a white seed of the Hopi variety
described as the male parent of hybrid Ah3.

Male 'parent. — White Chinese. The same as the male parent of
hybrid Dhl.

Hyhrid. — Plants fairly uniform, showing characters of both par-
ents. Ears remarkably uniform, more nearly resembling the female
parent. The only abnormal feature was the frequent exsertion of
the ear beyond the husks. Average height, 8 feet 4 inches. The 16
plants grown produced 28 ears and 2 nubbins, weighing 20.4 pounds.

HYBRID DH 4, CHINESE BY XUPHA.

Female parent. — Plant from a white seed of Chinese similar to the
male parent of hybrid Dhl.

Male parent. — A black, semistarch variety from Salvador. No
abnormalities. Average height, 8 feet 8 inches. The 14 plants
grown produced 21 ears and 5 nubbins, weighing 8.8 pounds.

Hyhrid. — The hybrid ear from which these plants were grown was
poorly matured. Plants and ears exhibited a number of abnormali-
ties. Eight suckers and two main stalks bore small ears at the base
of the tassel, below which were a number of supernumerary leaves.
In two cases the margins of the leaf sheaths were grown together,
forming a cylinder. About half of the ears produced staminate
flowers; some were interrupted and many had a long staminal portion
at the tip. Average height, 7 feet 10 inches. The 16 plants grown
produced 18 ears and 18 nubbins, weighing 8.6 pounds.

191

A NEW SERIES OF HYBRIDS BETWEEN DIVERSE TYPES. 25

HYBRID DH 6, BROWNSVILLE BY CHINESE.

Female 'parent. — A many-eared variety of white dent from Browns-
ville, Tex. The most striking peculiarity of this variety is the length
of the husks, which extend far beyond the tip of the ear and arc
tightly closed. Although the ear from which these plants were
grown was cross-pollinated, 9 seedlings out of 48 were albinos. The
yield of this variety would have been slightly higher if the growing
season had been longer, lower ears on many of the stalks being
immature. The plants were rather weak rooted and fell badly
before high winds. Average height, 9 feet 9 inches. The 15 plants
grown produced 25 ears and 8 nubbins, weighing 11.6 pounds.

Male 'parent. — White Chinese similar to the male parent of hybrid
Dhl.

Hybrid. — The plants showed few traces of the Chinese characters.
The ears were not lacking in uniformity. Husk characters similar to
the female parent. The full yielding power of this hybrid was not
shown on account of early frosts. No abnormalities. Average
height, 9 feet 6 inches. The 16 plants grown produced 35 ears and
17 nubbins, weighing 18.6 pounds.

HYBRID EH 1, HOPI BY ALGERIAN POP.

Female parent. — Same as the male parent of hybrid Ah3.

Male parent. — A type from Algeria with beaked grains that must
be classed as pop corn. Its most pronounced peculiarities are the
position of the ears, which are only 2 or 3 nodes from the top of the
plant, and the nature of the pericarp, which is semiopaque but not
colored. No abnormalities. Average height, 5 feet. The 16 plants
grown produced 20 ears and 6 nubbins, weighing 5.5 pounds.

Hybrid. — Plants uniform and intermediate. The ears produced
were quite unlike either parent, as large or larger than those of the
female parent, but with very small grains. The only abnormalities
were the production of ears at the base of the tassel on a few of the
suckers, two "bears' foot" ears, and one branched ear. Average
height, 9 feet 6 inches. The 15 plants grown produced 21 ears and 5
nubbins, weighing 13.6 pounds.

HYBRID GH 2, TOM THUMB BY QUEZALTENANGO BLACK.

Female parent. — A very small variety of pop corn. The plants are
from 8 inches to 2 feet in height and bear diminutive ears about 2 or
3 inches long. No abnormalities. The 6 plants grown produced 7
ears, weighing O.G pound.

191

26 VALUE OF FIRST-GENERATION HYBRIDS IN CORN,

Male parent— A very tall variety from the high mountains of the
western part of Guatemala. The ears are borne very near the top of
the plants and are consequently late in maturing. Although appar-
ently an unproductive type the yield here given is little indication of
what the variety might do if the season permitted maturing. The
cross was made to test the possibility of making crosses between
varieties that represented the extremes in size. Average height, 9
feet 6 inches. The 15 plants grown produced 9 nubbins, weighing

1.5 pounds.

Hybrid.— Plants intermediate but exhibiting considerable irregu-
larity in size. Ears averaging 7 inches long, fairly uniform. The
principal abnormality was shown m the leaves, which were crumpled
and distorted m all the plants. The color was so dark as to be
abnormal. While this cross showed distinctly an increase in vigor
over that of the parents, the yield of both parents was so small that
the amount of the increase should not be considered. Average
height, 6 feet 7 inches. The 15 plants grown produced 16 ears and
6 nubbins, weighing 6.25 pounds.'^

HYBRID KH 31, BROWNSVILLE BY GUATEMALA RED.

Female parent. — The same as the female parent of hybrid Dh6.

Male parent. — A red flinty-seeded variety with 12 to 16 rowed
ears, from the lowlands of Guatemala. No abnormalities. Average
height, 8 feet 11 inches. The 14 plants grown produced 6 ears and
12 nubbms, weighing 4.31 pounds.

Hybrid. — Ears fairly uniform. Plants and ears without abnor-
malities. Average height, 10 feet 2 inches. The 32 plants grown
produced 29 ears and 10 nubbins, weighing 15.6 pounds.

HYBRID KH 62, GUATEMALA RED BY SALVADOR BLACK.

Female parent. — The same as the male parent of hybrid Kh31.

Male parent. — A black variety from Salvador not unlike the female
parent. Two plants of this variety produced branched ears. The
ear stalks also curved up instead of down, so that the ears crossed
the main stem. The 15 plants grown produced 3 ears and 12 nubbins,
weighing 4.1 pounds.

oEast states "I have repeatedly tried to cross Giant Missouri Cob Pipe maize (14
feet high) and Tom Thumb pop maize (2 feet high), but have always failed. They
both cross readily with varieties intermediate in size, but are sterile between them-
selves." (See East, E. M., A Mendelian Interpretation of Variation that is Appa-
rently Continuous, The American Naturalist, vol. 44, 1910, p. 82.

It may also be noted that this small variety was successfully crossed with a large
Mexican dent whose average height was 11 feet 7 inches. In these experiments the
Giant Missouri Cob Pipe corn averaged only 8 feet 4 inches.
191

A NEW SEEIES OF HYBRIDS BETWEEN DIVERSE TYPES. 27

Hybrid. — Ears very irregular. One plant produced 2 ears, both
of which were interrupted. In many others the ears exceeded the
husks. The 16 plants grown produced 8 ears and 8 nubbms, weighing
5.25 pounds.

HYBRID MH 13, QUARENTANO BY BROWNSVILLE.

Female 'parent. — A drought-resistant variety from Chiapas, Mexico.
Many of the plants of this variety have very wide leaf sheaths that
are closely wrapped around the weak stalk and are the chief support
of the upper part of the plant. Average height, 7 feet 6 inches. The
16 plants grown produced 8 ears and 7 nubbms, w^eighing 4.3 pounds.

Male parent. — The same as the female parent of Dh6.

Hyhrid. — Plants and ears very diverse, w^ithout the peculiarities of
the female parent. Nine of the plants produced ears exceedmg the
husks. In three cases the ears were interrupted. The inner husks
w^ere crumpled at the base of the ear, a not uncommon condition with
thick-husked varieties. Average height, 11 feet 5 inches. This is
one of the two cases where the yield of the hybrid was below the
average of the parents. With such disparity between the yields of
the two parents this may mean that the Iwbrid more nearly resem-
bled the lower yielding parent. The 16 plants grown produced 11
■ears and 7 nubbins, weighmg 7.6 pounds.

HYBRID MH 15, HUAMAMANTLA BY HAIRY MEXICAN.

Female parent. — A drought-resistant variety with shoe-peg grains,
from Mexico. A variety of the hairy Mexican series, though not a
pronounced type. The tassels have a few very long primary branches.
The season the cross was made this variety had 50 per cent of the
ears interrupted. Plants grown from the same original seed in the
season of 1909 had no interrupted ears. Average height, 8 feet. The
1.3 plants gro^vTi produced 4 ears and 7 nubbms, w^eighing 5.2 pounds.

Male parent. — A pronounced type of the hairy Mexican series, with
superficial roots, hairy leaf sheaths, and usually unbranched tassels.
The poorly protected ears usually decay in the moist fall weather.
Average height, 7 feet 11 inches. The 16 plants grown produced 5
ears and 4 nubbins, weighing 2.8 pounds.

Hyhrid. — Plants irregular, exhibiting nearly the full range of both
parents. The stalks were rather weak; the tassels with from 3 to 7
branches. One ear was produced with a staminate portion at the tip.
Average height, 9 feet 1 inch. The 15 plants grown produced 7 ears
and 9 nubbins, weighing 4.6 pounds.

191

28 VALUE OF FIKST-GENEEATION HYBRIDS IN CORN.

HYBRID MH 16, ARRIBENO BY HAIRY MEXICAN.

Female parent. — Similar to the female parent of Mhl5, but a larger
variety. Average height, 9 feet. The 15 plants grown produced 10
ears and 7 nubbins, weighing 5.8 pounds.

Male imrent. — Same as the male parent of hybrid Mhl5.

Hyhrid. — Plants similar to hybrid Mhl5, but more robust and uni-
form. A striking characteristic of this cross was that the leaf blades,
though slightly shorter, were much broader than those of either
parent. The fifth blade of the hybrid averaged 31.3 by 5.6 inches.
The corresponding blade of the female parent averaged 35.4 by 4.1
and the male 31.5 by 4.7 inches. Average height, 9 feet. The 14
plants grown produced 9 ears and 7 nubbins, weighing 6.6 pounds.

HYBRID MH 17, HAIRY MEXICAN BY CHINESE.

Female parent. — The same as the male parent of hybrid Mill 5.

Male parent. — The same as the male parent of hybrid Dhl.

Hybrid. — Plants and ears fairly uniform. One difference between
the parent strains is that in the female parent when more than one
ear is produced at a node the secondary ear is borne directly in the
axil of the prophyllum. The male parent resembles the United States
varieties in havmg the first secondary ear borne in the axil of the first
husk. Of the hybrid plants that produce secondary ears one-half
resembled the male and one-half the female in this respect. The only
abnormalities noted were a tendency in a number of plants to have the
leaves on the upper part of the plant crowded and one ear with a
staminate spike at the tip. Average height, 7 feet 4 inches. The 16
plants grown produced 18 ears and 4 nubbins, w^eighing 9.8 pounds.

HYBRID MH 25, MEXICAN DENT BY TOM THUMB.

Female parent. — A large Mexican variety with a pronounced tend-
ency to produce large secondary ears. One interrupted ear was pro-
duced. Average height, 11 feet 7 inches. The 15 plants grown
produced 10 ears and 15 nubbms, weighing 7.8 pounds.

Male parent. — The same as the female parent of hybrid Gh2,
Hyhrid. — Plants resembling the female parent in most particulars.
About one-half the ears exceeded the husks. Average height, 6 feet
7 inches. The 16 plants grown produced 22 ears and 13 nubbins,
weighing 8.6 pounds. Though this cross would seem to have been
quite as violent as Gh2, no pronounced abnormalities were found.

YIELDS OF FIRST-GENERATION HYBRIDS.

The following table shows the behavior of the 16 crosses and their
parents. The yields are given as yield per plant and were calculated

191

YIELDS OF FIEST-GENEEATION HYBEIDS.

29

by dividing the total weight of the ears produced in the row by the
number of phmts. The plants w^ere started four in a hill and thinned
to one as soon as established.

Table IV. — Yields per plant of 16 corn hybrids compared with that of their parents.

Name of hybrid.

Ah3, Maryland dent by Hopi

Ah4, Tuscarora by Cinquantino

Dhl, Kansas dent by Chinese

Dh2, Chinese by Chihuahua

Dh3, Hopi by Chinese

Dh4, Chinese by Xupha

Dh6, Brownsville by Chinese

Ehl, Hopi by Algerian pop

Gh2, Tom Thumb by Quezaltenango black.

Kh31, Brownsville by Guatemala red

Kh62, Guatemala red" by Salvador black . . .

Mhl3, Quarentano by Brownsville

Mhl5, Huamamantla by Hairy Me.xican. . .

MhKi, Arribeiio by Hairy Mexican

Mhl7, Hairy Mexican by Chinese

Mh25, Mexican dent by Tom Thumb

Average percentage of increase of hy-
brids over average of parents

Yield of
female
parent.

Pounds.
1.19
.53
.99
.39
.74
.39
.77
.74
.10
. 77
.31
.27
.40
.39
.18
.52

Yield of

male
parent.

Average
yield of
parents.

Pound.
0.74
.24
.39
.69
.39
.63
.39
.34
.10
.31
.27
.77
.18
.18
.39
.10

Pound.
0.965
..385
.690
.540
.565
.510
.580
.540
.100
.540
.290
.520
.290
.285
.285
.310

Yield of
hvbrid.

Pounds.

1.25
.75

1.09
.95

1.28
.54

1.16
.91
.42
.49
.33
.48
.31
.47
.61
.54

Percentage
of increase
of hybrid

over

average of

parents.

Per cent.

29

95

58

76

126

6

100

69

C)

(a)

-9
14

-8

7

65

114

53

a Where the yield of either parent fell as low as 0.10 pound per plant the percentage of increase of the
hybrid is omitted. In dealmg with these small quantities it is believed that percentages would be
misleading.

Before leaving the subject of increased yields in firet-generation
hybrids it may be well to summarize the results of the experiments
bearing on this question.

To carefully canvass the literature of agriculture for all references
to the yield of first-generation hybrids would be a large undertaking,
and it is not pretended that the present summary is complete. It is
believed, however, that the experiments cited, which are all that have
come to the writer's attention, establish the wide application of the
principle and give a fair indication of its importance.

Beal (Michigan, 1878-80) in two crosses very carefully compared with the parent
varieties secured an increase in both cases, the average increase being 31 per cent.

Another cross by Beal (1882) compared with the best parent exceeded that parent
by 21 per cent.

Ingersoll (Indiana, 1881) in a cross between two strains of the same variety secured
an increase over the male parent of 95 per cent.

Sanborn (Maine, 1889) in one cross secured an increase over the average of the
parents of 41 per cent.

Morrow and Gardner (Illinois, 1892) secured increases in eight out of nine crosses,
the average increase being 11 per cent.

Shall (New York, 1908) by first inbreeding and then crossing got an increase over
the original mixed stock of 2 per cent.

East (Connecticut, 1908) secured increases in all of four crosses, the average increase
being 73 per cent.
191

30 VALUE or FIBST-GE^'EKATIO^' HYBEIDS IN CORN.

Experiments by the writer with primitive tj-pes crossed with one another and with
United States varieties, first reported in the present paper, gave increased yields in 1-4
out of 16 cases, the average increase being 53 per cent.

Though the average of the yields of the parent varieties may be
considered as a fair standard for judging the increased yields of the
hybrids from the standpoint of heredity, the practical value of
hybrids must be determined by comparing their yields with those of
the more productive parents. To secure evidence on this point it \s-ill
be necessary to consider the crosses wliich have been made between
good-yielding varieties gro^vn under favorable conditions, excluding
those in which there is great disparity in the yields of the parents.

The following table includes all the crosses here reported in which
the parents appear to have been fair-yielding standard varieties
giving approximately the same yields.

Table V. — Increased yield of hybrid corn over the more productive parent.

Percentage

of increase

of hybrid

over better

parent.

Beal (p. 11). ''Varieties essentially alite"

Beal (p. 11). "Varieties essentially alike"

Beal (p. 12). Hybrid compared only with, better parent

IngersoU (p. 12). Strains of the same variety

Morrow and Gardner (p. 15). Parents differed by 2.6 bushels per acre. .
Morrow and Gardner (p. 15). Parents differed by 15.0 bushels per acre.
Morrow and Gardner (p. 15). Parents differed by 8.5 bushels per acre. .
Morrow and Gardner (p. 15). Parents differed by 13.0 bushels per acre.
Morrow and Gardner (p. 15). Parents differed by 5.8 bushels per acre..

51

10
21
95

—8

17

4
18

It will be seen fi-om Table V that in six of the nine crosses signifi-
cant increases were obtained over the yield of either parent, and two of
the tlu'ee exceptions should, perhaps, have been excluded, since the
differences between the }4elds of the parents were 15 and 13 bushels,
respectively.

The experiments thus far reported are too few to warrant any
conclusions regardins: the nature of the crosses wliich mav be rehed
upon to yield the greatest increase. It is naturally to be expected
that the percentage of increase will be greatest between low-yieldmg
strains, but the greatest increase in bushels per acre may follow the
crossing of the more highly developed strains.

Probably none of the crosses here considered were between care-
fully bred and locally adjusted strains, ^liat the results of such
crosses will be is yet to be determined.. Since the most carefuUy
selected strains are more or less inbred, a substantial increase would
be expected from crossing two such unrelated inbred strains unless
they have already approached the limit of production of the com
plant.

191

EXTENSION OF COEN CULTURE BY HYBRIDS. 31

Experiments similar to those conducted by Sliull may have a
special bearing in this connection. The reduction in vigor which
accompanies the inbreeding to which his strains are subjected would
have an effect similar to growing the plants under adverse conditions
and would tend to eliminate all but the strongest individuals. This
would, in fact, constitute an effective form of selection, and with
such strains thrown into the vigorous condition of first-generation
hybrids a maximum performance might be expected.

While the best results may in general be expected from crossing
two varieties both of which are productive, crossing with a low-
yielding variety may operate to increase the yield above that of a
much higher yielding variety with which it is crossed. The Chinese
variety mentioned on page 23 is a small variety producing only 0..39
pound per plant in the experiments reported. Yet in four of the
five cases where this variety was crossed with higher yielding varieties
the yield of the hybrid exceeded that of the variety with wliich it was
crossed. The average yield of the five varieties with which the
Chinese corn was crossed was 0.764 pound per plant, nearly double
that of the Chinese, yet the average yield of the five hybrids was 1 .004
pounds per plant, an increase over the highest yielding parent of
nearly 33 per cent. If the increased vigor of hybrids is in any way
associated with the distinctness of the parent types, the remarkable
behavior of this series of crosses may perhaps be understood. This
Chinese variety is one of the most divergent types and must have
been isolated from all ordinary types of corn for a very long time.
Evidence was presented in a former publication " that the introduc-
tion of corn in China was probably pre-Columbian. In these and
other crosses where low-yielding varieties producing more than one
ear to the plant operated to increase the yield of larger-eared types,
the greater yields appeared to have been brought about by an
increase in the number of ears with only a slight reduction in their
size.

EXTENSION OF CORN CULTURE BY FIRST-GENERATION HYBRIDS.

In addition to increased vield in corn-growing regions the vigor of
first-generation hybrids may also allow of an extension of corn grow-
ing beyond the present area of production.

Even a slight increase in the drought resistance of corn would
make possible the extension of corn culture into large regions where
the growing of this crop is now too precarious to justify the effort.
The subject is of such importance as to warrant the investigation of
every possibility.

«A New Type of Indian Corn from China, Bulletin l(jl, Bureau uf Plant Industry,
U. S. Dept. of Agriculture, 1909, pp. 20-24.
191

32 VALUE OF FIRST-GENERATION HYBRIDS IN CORN.

That the utihzation of first-generation hybrids will be found of
special value in the drier parts of the country was clearly indicated
by the behavior of the hybrids described in these pages.

The season during which these hybrids were grown was one of
exceptional drought, affording an excellent opportunity for observing
the (Irought-resisting ability of the different strains and their hvbrids.
The rainfall at Washington, D. C, for April, May, and June was
slightly below the average, and for July and August it was 4.07
inches, less than one-half the normal.

The series included varieties from localities with such extremes of
climate as obtain in the plateau region of Mexico and the moist
Tropics of the lowlands of Central America. While the differences
between the varieties in their ability to withstand drought were
obvious, the most striking differences of this kind were between the
hybrids and the pure strains. Almost without regard to the nature
of the parents the hybrids remained dark green and vigorous when
nearly all of the pure strains were giving evidence of the lack of mois-
ture by their curled leaves and yellow color. This ability to with-
stand drought may have been a factor in the increased yields which
the hybrids produced.

Experiments are being made with a series of hybrids in western
Kansas and the dry Southwest with the idea of learning which crosses
will prove best suited to these extreme conditions.

Experiments at the Virginia Agricultural Experiment Station
indicate that first-generation hybrids may be found to withstand
excessive moisture as well as drought. Wliile the crosses were
apparently inidertaken with the idea of establishing hybrid varieties,
the results so far as reported apply only to the first generation.

The native varieties that were crossed with the western corns have developed, three
or four good strains, and out of some 350 samples tested here this j^ear none have stood
the wet season and made as good yields as the improved strains obtained by crossing
pure-bred western corn with our best native varieties. o

Associated with the general increase in vigor in first-generation
hybrids a certain measure of disease resistance may naturally be
expected. Many plant diseases that are unable to attack vigorous
plants are able to do serious damage to weaker varieties or to plants
that are weakened by adverse conditions. The ability of the hybrids
to resist drought might at the same time ])rotect them against disease.

In the case of the corn smut, which was the only disease that
affected any of the experiments, this factor of disease resistance does
not appear to apply^ for the attacks of the smut do not seem to

« Vanatter, Phares O. Annual Report, Virginia Agricultural Experiment Station,
1906, p. 55.
191

HYBRIDS AND CENTRALIZED SEED PRODUCTION. 33

depend upon the vigor of the phmts; Nothing approaching immunity
to this disease lias been observed in any of the varieties or the hybrids.'^

FIRST-GENERATION HYBRIDS AND CENTRALIZED SEED

PRODUCTION.

It is coming to be generally recognized that in corn culture the use
of seed not produced locally is a bad practice, and this is especially
true of the most carefully selected varieties. The stimulus to the
production of high-grade strains of corn is seriously weakened by the
extremely circumscribed area in which such strains can be grown
advantageously without further selection. Men of exceptional skill
and experience who devote their whole time to the development of
improved strains can, without doubt, do more effective work in selec-
tion than the farmer who is pressed with other work. But as soon as
a carefully selected strain is placed under conditions different from
those under which it was developed it behaves in a more or less
abnormal manner, and appears at a disadvantage when compared with
locally adjusted varieties. This factor of local adjustment is so
important that if carefully selected strains are to be directly utilized
in commercial production the centralization of seed growing must be
discouraged. Farmers must be urged to select their own seed or to
secure it from a local breeder.

That first-generation hybrids are relatively free from the new-place
effects that so seriously interfere with the spread of varieties has not
been demonstrated in corn, but may confidently be expected from the
analogy of first-generation hybrids in other crops.'' This does not
mean that a given cross will do equally well in all parts of the country,
but that it will make little difference whether the crossing is done in
one part of the country or another. When it is once ascertained which
combination of varieties is best adapted to a particular locality, pure
seed of these varieties may be maintained and the crosses made under
the supervision of a trained plant breeder at a central station.

« It was repeatedly observed that plants affected with smut were darker green and
more vigorous than neighboring plants not affected. This difference was noticed
especially in a strain that had been reduced in vigor by self-fertilization. In this case
but one plant in the row was affected with smut, and the stalk of this plant measured
3.82 inches in circumference, while the largest of the healthy plants measured only
3.15 inches. The leaves were also broader and dark green, while all the other plants
were yellow and spotted.

Except for the deformed parts where the fungus fruited, the smutted jilant appeared
more nearly normal than any of the others. The presence of the fungus seems in some
way to restore the vigor lost through self-fertilization.

b Cook, O. F. Local Adjustment of Cotton Varieties. Bulletin 159, Bureau of Plant
Industry, U. S. Dept. of Agriculture, 1909.
191

34 VALUE OF FIRST-GENEBATION HYBRIDS IX CORN.

Careful seedsmen who wish to extend the range of territory to which
they can supply seed that will be equal or superior to the best locally
selected seed should be willmg to give careful consideration to the
possibility of establishing regular supplies of first-generation hvt)rid
seed for their customers. "^

FIRST-GENERATION HYBRIDS IN SWEET CORN. ^g_

While the production of sweet corn is influenced b}' very difTerent
considerations from the production of field corn, the evidence at hand
indicates that the advantages of first-generation hybrids apply to
sweet corn with even greater force than to field corn.

In sweet corn, as with field corn, the yield is an important item, and
the experimental data here presented warrant the statement that the
yield can be very materially increased by means of first-generation
hybrids.

With sweet corn, however, the }'ield is not the only consideration;
quality and uniformity are important factors that must be taken
into consideration. As regards quality, the evidence indicates that
in most cases it wall be intermediate between that of the parents. If
parents of good quality are chosen, the quality of the hybrid will be
satisfactory. The proof of this rests not alone on the few cases
where the quality of the first generation of crosses of sweet-corn
varieties has been recorded, but on the general fact that the morpho-
logical characters of the first generation of crosses in corn are almost
always intermediate between those of the parents. With respect to
uniformity it may be said that experiments in crossing sweet varieties
have not been recorded in such a way as to give direct evidence.
On the other hand, experiments in the crossing of field corns make
it certain that in this class, with properly chosen varieties, a perfectly
satisfactors' degree of uniformity can be secured. The first genera-
tion of a cross is usually quite as uniform as the parent strains, a
condition natural!}' to be expected in view of the general tendency
for all morphological characters to appear intermediate in the first
generation. While the strict uniformity requii-ed in score-card rat-
ings may not be assured, it is altogether probable that the uniformity
of size, color, shape, and time of maturing required by the market
will be fully met if reasonabh-^ uniform strains are selected as parents.

The important differences between sweet and field corn in the
commercial methods of producing and handling seed are all of a
nature to make the application of this })rinciple more effective with
sweet corn than with field corn. A much larger percentage of sweet-
corn than of field-corn growers buy their seed, a practice that is
much to be regretted where pure strains are used, since the lack of

191

METHODS FOR TESTING COEN HYBRIDS. 35

local adjiistinent interferes with the proper performance of superior
and carefully selected strains, even when the seed is carried only a
short distance. First-generation hybrids are to a great extent inde-
pendent of this delicate adjustment to local conditions. The utili-
sation of first-generation hybrids would tend to obviate the neces-
sit}' of urging each farmer to breed his own sweet corn, a practice
which must surely follow if the highest performance of pure strains
Is to be secured.

The possibility of growing combinations of highly bred strains over
wide areas would enable the work of the few really skilled breeders
of sweet corn to be much more effective. While the general ])rinciple
is very simple and of wide application, its fidlest utilization will
require a large amount of experimentation to determine the best
combinations for each locality and market. A thorough knowledge
of the existing varieties would be of the greatest value to anyone
undertaking this work, and, as the cross has to be made anew each
year, the inventor of a new and superior combination could much
more effectively guard his discovery and secure a more adecjuate
reward for his work than is possible to the breeder of a pure strain.

While further experiments are needed to establish the assumption
that crosses of sweet-corn varieties will behave essentially the same
as crosses of varieties of field corn, the following possibihties of first-
generation hybrids are defuiitely indicated: (1) Increased yield, (2)
uniformity equal to that of the parents, (3) quahty intermediate
between the parents, (4) increased immunity from disease, (5) exten-
sion of the industry into new territory, (6) less localization of highly
bred strains, (7) increased utilization of the work of experienced
breeders, and (S) stimulus to the work of improvement through the
possibility of protecting new productions.

METHODS FOR TESTING CORN HYBRIDS.

It is lioped that the present summary of facts and possibilities
regarding first-generation hybrids will assist in stimulating experi-
ments, especially by those who are in a ])osition to keep careful rec-
ords and report the results.

The ex})eriments are of such a simi)le nature and results nuiy be
expected in such a relatively short time that those interested in
increased yields should be concerned to learn the possibilities of this
method for their particular localities and varieties and to report the
results of their experiments as a contribution to the better under-
standing of the principles involved. Exceptions are to be expected,
though none that may not be ascribed to experimental error have
yet been reported.

191

36 VALUE OF FIKST-GENEEATION HYBRIDS IN CORN.

From the standpoint of the investigation the faihn-es of such
experiments are often of even greater interest than the successes,
since they may lead to better understandings of the factors involved-

In reporting results it would seem desirable to state the facts
bearing upon as many of the following points as ])ossible:

(1) Names and descriptions of varieties crossed. — While the names
of commercial varieties are almost hopelessly confused, some desig-
nations are necessary for purposes of reference, and if these are accom-
panied by careful descriptions many errors may be avoided, as well
as a needless duplication of work.

(2) History of the varieties. — This should be traced as far back as
possible to throw light on the degree of relationship that exists between
the varieties crossed.

(3) Sources of seed and previous methods of breeding. — Important
differences may be expected even where the same varieties are used,
depending on whether the seed has been self-pollinated or cross-
pollinated; also whether it was the result of mass selection in the
field or crib or was derived from a single ear.

(4) Size of the hybridizing plat and the plats or rows in which the
yields are tested. — The ratio between the area devoted to each variety
in the breeding plat and that in which the yield test of the same
variety is made should be recorded, since it is a measure of the oppor-
tunity for selection. If the breeding or hybridizing plat is small in
proportion to the area to be planted, it will be necessary to save a
large part of the seed for planting and the opportunity for selection
will be correspondingly small. The failure to take this fact into
consideration is one of the reasons why large field plantings of pure-
bred varieties so frequently fail to meet expectations of high yields
indicated in the breeding ])lats, where a more rigid selection was
practiced.

(5) Extent of self-pollination in the parent varieties. — Many varieties
produce pollen so little in advance of the silks that a considerable
proportion of the seed is self-pollinated, and this operates to diminish
the yield of the resulting plants. In such cases a part of the increase
that might be ascribed to the crossing of two varieties would in
reality be due to the depressed yields of the })arent varieties with
which the cross is compared. To determine the increase actually
due to the crossing, seed from detasseled plants of the parent varie-
ties should be included in the yield test, together with ordinary wind-
pollinated seed of the same varieties.

(6) The method by whicli the yields are compared and the precautions
against experimental error. — In this connection it should be borne in
mind that large })lats do not insure greater accuracy. The larger
the ])lat the greater the difliculty of obtaining equal conditions.

191

DIFFERENT METHODS OF PRODUCING HYBRID SEED. 37

Much greater accuracy can be secured by a comparison of a series of
single rows or narrow plats and repeating the series as many times
as space or seed will permit.

DIFFERENT METHODS OF PRODUCING HYBRID SEED.

While the process of securing hybrid seed is very simple, it is pos-
sible to vary the details of the method to suit different objects and
conditions. Those wishing to experiment with a considerable
series of hybrids will find it convenient to select what is considered
the most promising variety for the male parent and plant this variety
in every other row. Any number of other varieties can then be
planted in the alternate rows and carefully detasseled. Hybrids
will then be secured between the variety selected as a male parent
and each of the others, and the seed will be in sufficient quantity to
make accurate yield tests the following season.

If it is desired to keep accurate pedigrees of individual j)lants,
resort must be had to hand pollination.

The production of hybrid seed on a commercial scale also permits
of considerable variety in the details of the method. Whatever
method is followed it would seem desirable that the plat in which the
hybrid is made be large enough to afford opportunity for selection.
The actual size of the seed plat should be governed by the size of the
field planting to be made the following season and the ratio should
not be greater than 1 to 100. Thus, if the contemplated field plant-
ing is to be 50 acres the hybridizing plat should not be less than half
an acre.

Perhaps the most sim])le method for the farmer is to purchase each
year a small quantity of seed of two varieties that are known to be
well adapted to the particullar section and plant in alternate rows in a
hybridizing plat, as recentlji recommended by Doctor East."

The varieties must, of course, be of nearly the same length of sea-
son, and in case of any difference in this respect the variety that
flowers early should be chosen for detassehng. If the farmer wishes
to grow his own parent varieties he can do so by alternating the male
and female parents each succeeding year and selecting enough seed
from the variety not detasseled to supply the hybridizing plat for two
years, the first year as the female parent and the following year as the
male. The same result could be approximated by detassehng one of
the varieties in one half of the field and the other variety in the other
half of the field. By this method seed of both varieties would be
secured each year, but considerable indiscriminate crossing would
take place.

a The Rural New Yorker, May 1 and 8, 1909.
101

38 VALUE OF FIRST-GEXERATIOX HYBRIDS IX CORX.

One difficulty, however, with this reciprocal use of male and female
parents would arise unless the varieties agree in length of season.
Xo difficulty would be experienced in securing perfect pollination in a
short-season variety used as the female parent, but if such a variety
were expected to serve as the male parent the tendency to the early
shedding of the pollen might leave little or none available for ferti-
lizing a later variety used as a female parent.

The following directions, which have been sent out to several
cooperative experimenters, give a concrete example of one of the
ways in which the value of first-generation hybrids may be deter-
mined :

Experiments as outlined below involve the use of tw'o varieties and two separate
plats. Varieties may be designated as Xo. 1 and Xo. 2, the plats as A and B. The
plats should be sufficiently separated to prevent cross-pollination between them.

It should be kept in mind that the increased \-ield can be expected only for the one
year immediately following that in which the cross is made.

Plat A is planted with alternate rows of Xo. 1 and Xo. 2. The rows planted with Xo.
2 are to have all plants detasseled. The crop of Xo. 1 and Xo. 2 is to be saved sepa-
rately.

Plat B is planted entirely with variety Xo. 2 and has alternate rows detasseled.
The crop from the tasseled and detasseled rows is to be saved separately.

At harvesting there will be the following lots of seed:

(1) Plat A. Variety No. 1, field-pollinated.

(2) Plat A. Hybrid between Xo. 1 and Xo. 2.

(3) Plat B. Variety Xo. 2, field-pollinated.

(4) Plat B. Variety Xo. 2, cross-pollinated.

The yields in the year the cross is made should show the comparative value of the
two varieties and the effect, if any, of detasseling on the immediate j-ield.

A comparison of the j-ield from these four lots of seed the following year should show
the }-ield of the first -generation hybrid as compared with the pure varieties and to what
extent the increase, if any, is due to the elimination of self-pollinated seed.

If plat B can not be proWded, seed of variety Xo. 2 should be held for planting the
following year in comparison with variety Xo. 1 and the hybrid seed.

If it is considered important to have the crop of a uniform color, yel-
low and white varieties should not be crossed, for the grains will be of
different colors in the year foUowing the cross. Crosses between dent
and flint or between these and sweet corn would also result in a lack of
uniformity with respect to the character of the seed. That such differ-
ences should occur while the other characters remain so nearly uni-
form may appear remarkable, but is explained by another of the
pecuhar habits of the corn plant. UnUke most other plants the seeds
of corn show an immediate effect of pollen (xenia).* If a white-
seeded varietv is crossed bv one with vellow or black seeds, the new
seeds that are produced show the color of the male parent.

" For a discussion of xenia, see Webber, H. J., Bulletin 22, Division of Vegetable
Physiology and Pathology, U. vS. Dept. of Agriculture, 1900.
191

COXCLUSIOXS. 39

The embiyo that forms as a result of a cross-pollmation is, of
course, hybrid in nature and may differ from the female parent.
Owing to a peculiar double fertilization that obtauis m corn the
developing endosperm as well as the embryo is contributed to by
the pollen and may resemble the male parent. With respect to the
characters of the endosperm we are already dealing with the first
generation of a hybrid and the general law of uniformity in the fii-st
generation seems to hold in most instances. There may be no pre-
dicting what the nature of the grain will be, but those plants resulting
from the same cross may usually be depended upon to be alike.

The diversity that appeare in the seed color of fu"st-generation
hybrids is only an apparent exception to the general iiile of uniform-
ity in first-generation hybrids. The endosperm in which this diver-
sity appeal's is in reality the second generation of the hybrid and
may consequently show the diversity characteristic of second-genera-
tion hybrids.

CONCLUSIONS.

The com plant is naturally cross-fertilized and requires the stimulus
of crossing to produce maximum yields. Methods of close breeding
that can be applied to other crops with advantage do violence to
the nature of the plant and tend to reduce the vigor of growth and
the yield of grain.

As a result of the peculiar habits of reproduction of the corn plant,
the raising of hybrid seed does not require any special skill or any
large increase of labor. The cost involved is insignificant in com-
parison with the increased yields that are obtamed.

Xo reason is apparent why the vigor of hybrids may not be regularly
utilized to increase the yields of the corn crop. A refusal to take
this factor mto account would be like rejectmg the use of commercial
fertilizers or failing to take advantage of the increase that may be
obtained by selective breedmg.

The plantmg of fu-st-generation hybrid seed as a method of secur-
ing a larger crop is to be considered as entirely distinct from the idea
that superior varieties can be bred by hybridizmg or crossing. Crosses
between distinct varieties or strains at once increase the yield, but to
maintain this high performance the cross must be made anew each year.

Experiments to determme the value of fii-st-generation hybrids
have been made at various times since 1878, but in an isolated and
disconnected manner and usually without any adec[uate apprecia-
tion of the possibilities of this method as a regidar element of farm
practice.

In the literature which has thus far been examined, 19 crosses have
been reported. With a single exception these hybrids gave larger

191

40 VALUE OF FIRST-GENERATION HYBRIDS IN CORN.

yields than the average of the parents, the amount rangmg as high
as 95 per cent. The series inckides experiments in six different States
and embraces a wide range of varieties.

Similar increases are here reported in crosses between the mem-
bers of a new series of types of corn from China, Africa, and the
American Tropics, very different from United States varieties and
very unlike among themselves. These experiments show that a very
wide application of this principle is possible.

In addition to increased yields there is reason to believe that the
increased vigor of first-generation hybrids may become an important
factor of adaptation to different conditions of growth. Tlie hyl)rids
appear not to require the delicate adjustment to local conditions
necessary to the pro])er performance of pure strains. The utiliza-
tion of hybrids may be expected to extend the range of utility of the
high-yielding types beyond the present range of adaptation of such
varieties.

First-generation hybrids are a distinct factor in the problem of
securing varieties of corn with adaptations that fit them for special
conditions. The increased vigor which these hybrids possess should
make possible their growth in regions where pure strains fail and
should also provide some measure of disease resistance.

The advantage of crossing distinct varieties is equally ap{)licable to
the improvement of sweet corn and affords a measure of protection
to those discovering new and valuable combinations.

191

INDEX

Algerian pop com. See Corn, pop, Algerian.

Arribeno corn. >Sfe Corn, Arribeiio. Page.

Bartholomew , Elam, development of Kansas dent corn 23

Beal, W. J., experiments with first-generation corn hybrids in Michigan. 10-12, 29, 30

Beans, black wax, crossing, experiments in ^lichigan 11

Black Mexican X Queen's Golden corn. See Corn, Black Mexican X Queen's
Golden.
White dent corn. See Corn, Black Mexican X \Miite dent,
wax beans. See Beans, black wax.

"Bonafous, M., description of drought-resistant corn in Mexico 20

Brownsville corn. See Corn, Brownsville.

Burr's ^^^^ite X Cranberry corn. See Corn, Burr's White X Cranberry.
Edmonds corn. See Corn, Burr's ^Miite X Edmonds.
Helm's Improved corn. See Corn, Burr's AMiite X Helm's
Improved.
Champion WTiite Pearl X Burr's White corn. -See Corn, Champion "WTiite Pearl

X Burr's Wliite.
Leamingcorn. See Corn, Champion Wliite Pearl X
Leaming.
Chihuahua corn. See Corn, Chihuahua.

China, pre-Columbian corn introduction 31

Chinese com. See Corn, Chinese.

Cinquantino corn. See Com, Cinquantino.

Common Pearl pop corn. See Corn, pop. Common Pearl.

Conclusions of bulletin 39-40

Connecticut, experiments with first-generation corn hybrids 18-20, 29

Cook, O. F., on first-generation hybrids in various crops 33

Corn, Arribeno, crossing, experiments 28, 29

Black ]\Iexican X Queen's Golden, crossing, experiments 14-15

WTiite dent, crossing, experiments 14-15

Brownsville, crossing, experiments 25, 26, 27, 29

Burr's ^\'hite X Cranberry, crossing, experiments 15-16

Edmonds, crossing, experiments 15-16

Helm's Improved, crossing, experiments 15-16

('hampion Wliite Pearl X Burr's AMiite, comparison with parent varieties. 16-17

Leaming, crossing, experiments 15-16

Chihuahua, crossing, experiments 23-24, 29

Chinese, crossing, experiments 23-24, 24, 25, 28, 29

pre-Columbian introduction 31

Cinquantino, crossiug, experiments 22-23, 29

cross-fertilized and self- fertilized, experiments in Indiana 12

crossing, experiments in Connecticut 18-20, 29

Illinois 13-17, 29, 30

Indiana 12, 29, 30

191

41

42 . VALUE OF FIKST-GENERATION HYBRIDS IN CORN.

Page.

Corn, crossing, experiments in Michigan, early 10-12, 29, 30

New York 17-18, 29

closely related strains 17-18, 29

self-fertilized strains 17-18

studies, value, etc 9, 15-17

two varieties, benefits and methods 15-17

increasing yields 8, 10-20

culture, extension by first-generation hybrids 31-33

importance of locally produced seed 33-34

value of first-generation hybrid seed 3.3-34

dent, crossing, experiments in Illinois 13-15

diverse types, crossing, experiments 20-28, 29

drought resistance, increase, experiments 31-33

resistant type developed in Mexico 20-21

value in extension of corn culture 31-33

Edmonds X Burr's White, comparison with parent varieties 16-17

Murdock, comparison with parent varieties 16-17

Flour, second-year crossing 13-15

flowering habits, studies 8

Giant Missouri Cob Pipe, crossing, experiments 26

Gold Coin X Eight-rowed, crossing, experiments 14-15

Flour, crossing, experiments 14-15

Triumph, crossing, experiments 14-15

second-year crossing 13-15

Guatemala red, crossing, experiments 26-27, 29

Hairy Mexican, crossing, experiments 27, 28, 29

Hopi, crossing, experiments 22, 24, 25, 29

Huamamantla, crossing, experiments 27, 29

hybrid Ah 3, Maryland dent X Hopi, crossing, experiments 22, 29

4, Tuscarora X Cinquantino, crossing, experiments 22-23,29

Dh 1, Kansas dent X Chinese, crossing, experiments 23,29

2, Chinese X Chihuahua, crossing, experiments 23-24, 29

3, Hopi X Chinese, crossing, experiments 24, 29

4, Chinese X Xupha , ... 24, 29

6, Brownsville X Chinese, crossing, experiments 25, 29

Eh 1, Hopi X Algerian pop, crossing, experiments 25, 29

Gh 2, Tom Thumb X Quezaltenango black, crossing, experi-
ments 25-26, 29

Kh 31, Brownsville X Guatemala red, crossing, experiments 26, 29

62, Guatemala redx Salvador black, crossing, experiments. 26-27, 29
Mh 13, Quarentano X Brownsville, crossing, experiments 27,29

15, Huamamantla X Hairy Mexican, crossing, experiments. . 27, 29

16, Arribeiio X Hairy Mexican, crossing, experiments 28, 29

17, Hairy Mexican X Chinese, crossing, experiments 28, 29

25, Mexican dent X Tom Thumb, crossing, experiments 28, 29

hybrids, diverse types, new series 20-28, 29

first-generation, and centralized seed production 33-34

comparison with parent varieties 15-16, 28-31

confusion with hybrid varieties 8-9

disease resistance 32-33

effect of vigor on production 9, 39-40

experiments, previous 10-20

191

I

INDEX. 43

Page.

Corn, hybrids, first-generation, production, number, value, etc 7, 8, 28-31, 39-40

superiority, popular belief 9-10

use in extension of corn culture 31-33

value, statement of W. W. Tracy 10

yields 28-31, 39-40

hand-pollinated, production and value 8-9

in New York 17-18, 29

seed, methods of production 37-39

" ! I . self-fertilization, results on size of ear 14-15

testing, methods 35-37

vigor a factor of production 9, 39-40

yield, increase over better parent 30-31

See also Corn, sweet, hybrids,
improvement, cooperative crossing experiments at various agricultural

schools 11

in Indiana 12

Maine 13

isolation of pure strains, experiments in New York 17-18

Kansas Dent, crossing, experiments 23, 29

Leaming X Burr's White, comparison with parent varieties 16-17

Eight-rowed, crossing, experiments 14-15

Golden Beauty, crossing, experiments 15-16

Mammoth, crossing, experiments 14-15

Triumph, crossing, experiments 14-15

Longfellow, crossing, experiments in Connecticut 18-20

Maryland Dent, crossing, experiments 22, 29

Mexican Dent, crossing, experiments 26, 28, 29

Pignoletto, importation from Hungary, description 22-23

plant, habits 8, 39

pop, Algerian, crossing, experiments 25, 29

Common Pearl, second-year crossing 13-15

crossing, experiments in Illinois 13-15

Queen's Golden X Common Pearl, crossing, experiments 14-15

second-year crossing 13-15

pre-Columbian, introduction in China 31

Quarentano, crossing, experiments 27, 29

Queen's Golden X White Dent, crossing, exj^eriments 14-15

Quezaltenango black, crossing, experiments 25-26, 29

Salvador black, crossing, experiments 26-27, 29

second-year crossing, experiments in Illinois 13-15

seed, hybrid, methods of production 37-39

production, centralized, and first-generation hybrids. 33-34

local, importance 33-34

self-pollinated and cross-pollinated seed, comparison of yield in New

York 18

smut. Sec Smut, corn.

soft, crossing, experiments in Illinois 13-15

Stowell's X Eight-rowed, crossing, experirrients 14-15

Gold Coin, crossing, experiments 14-15

Mammolh, crossing, experimonls 14-15

Triumph, crossing, experiments 14-15

Sturges's hybrid, crossing, experiments in Connecticut 18-20

191

44 VALUE OF FIRST-GENERATION HYBRIDS IN CORN.

Page.

Corn, susceptibility of plant to hybridization 8, 39

sweet, crossing, experiments in Illinois 13-15

hybrids, first-generation, influence on yield and quality 34-35

possibilities 35

Learning, second-year crossing 13-15

seed selection, value and method 34-35

Tom Thumb, crossing, experiments 25-26, 26, 28, 29

Tuscarora, crossing, experiments 22-23, 29

White Dent X Queen's Golden, crossing, experiments 14-15

Yellow Dent, crossing, experiments in Connecticut 18-20

crossing, experiments in Connecticut 18-20, 29

Indiana 12

Michigan 10-11

wind pollinated 8, 39

Xujiha, crossing, experiments 24-25, 29

Yellow dent X White dent, crossing, experiments in Connecticut 18-20

crossing, experiments in Connecticut 18-20

Michigan 10-11

flint X White dent, crossing, experiments in Connecticut 18-20

yield, increasing, use of first-generation hybrids 9, 39-40

East, E. M., experiments with first-generation corn hybrids in Connecticut. 18-20, 29

statement of corn-crossing experiment 26

Edmunds X Burr's white corn. See Corn, Edmonds X Burr's white.

Murdock corn. See Corn, Edmonds X Murdock.
Flour corn. Sec Corn, Flour.
Gardner, F. D., and Morrow, G. E., experiments with first-generation hybrids

in Illinois 15-17,29,30

Giant Missouri Cob Pipe corn. See Corn, Giant Missouri <'(ib Pipe.
Gold Coin X Eight-rowed corn. See Corn, Gold Com X Eight rowed.
Flour corn. See Corn, Gold Coin X Flour.
Triumph corn. -See Corn, Gold Coin X Triumph,
corn. See Corn, Gold Coin.
Guatemala red corn. See Corn, Guatemala red.
Hairy Mexican corn. See Corn, Hairy Mexican.
Hopi corn. See Corn, Hopi.
Huamamantla corn. Sec Corn, Iluamamantla.
Hybrids, corn. See Corn, hybrids.

Illinois, experiments with first-generation corn hybrids 13-17, 29, 30

Indiana, experiments with first-generation corn hybrids 12, 29, 30

IngersoU, C. L., experiments with first-generation corn hybrids in Indiana.. 12, 29, 30

Introduction to bulletin 7 8

Kansas dent corn. See Corn, Kansas dent.

Learning X Burr's White corn. See Corn, Leaming X Burrs ^^^lite.
Eight-rowed corn. Sec Corn, Leaming X Eight-rowed.
Golden Beauty corn. See Corn, Leaming X Golden Beauty.
Mammoth corn. See Corn, Leaming X Mammoth.
Triumph corn. See Corn, Leaming X Triumph.
sweet corn. See Corn, sweet, Leaming.
Longfellow corn. See Corn, Longfellow.

McCluer, G. W., experiments with first-generation corn hybrids in Illinois 13-17

Maine, experiments with first -generation corn hybrids 13, 29

Maryland, corn-crossing experiments - 21-28, 29

191 -.

INDEX. 45

Page.
Maryland dent corn. See Corn, Maryland dent.
Mexican dent corn. See Corn, Mexican dent.

Mexico, development of drought-resistant corn 20-21

Michigan, experiments with first-generation corn hybrids 10-12, 29, 30

Morrow, G. E., and Gardner, F. D., experiments with first-generation corn

hybrids in Illinois 15-17,29,30

New York, experiments with first-generation corn hybrids 17-18, 29

Pignoletto corn. See Corn, Pignoletto.
Pop corn. See Corn, pop.
Quarentano corn. See Corn, Quarentano.

Queen's Golden X Common Pearl pop corn. See Corn, pop. Queen's Golden
X Common Pearl.
White dent corn. See Corn, Queen's Golden X White dent,
pop corn. See Corn, pop, Queen's Golden.
Quezaltenango black corn. See Corn, Quezaltenango black.
Salvador black corn. See Corn, Salvador black.

Sanborn, J. W., -experiments with first-generation corn hybrids in Maine 13, 2!)

Seed, corn. See Corn, seed.

Shull, G. II., experiments with first-generation corn hybrids in New York . 17-18, 29

Smut, corn, effect on first-generation hybrids 32-33

Stowell's X Eight-rowed corn. See Corn, Stowell's X Eight rowed.
Gold Coin corn. See Com, Stowell's X Gold Coin.
Mammoth com. See Corn, Stowell's X Mammoth.
Triumph corn. See Corn, Stowell's X Triumph.
Sturges's hybrid corn. See Corn, Sturges's hybrid.

Summary of bulletin 39-41

Sweet corn. See Corn, sweet.

Tom Thumb corn. See Com, Tom Thumb.

Tracy, W. W., statement regarding value of first-generation hybrids 10

Tuscarora corn. See Corn, Tuscarora.

Vanatter, P. O., on corn crossing 32

Webber, II. J., corn crossing, reference 38

White dent X Queen's Golden corn. See Com, White dent X Queen's Golden.
Yellow dent corn. See Com, White dent X Yellow dent,
com. See Corn, White dent.
Xupha corn. See Corn, Xupha.

Yellow dent X White dent corn. See Corn, Yellow dent X White dent,
corn. See Corn, Yellow dent.
flint X White dent corn. See Corn, Yellow flint X White dent.

Zea hirta, drought-resistant type of corn in Mexico 20-21

11)1

o

[Continued from page 2 of cover.] "i

No. 107. American Root Drugs. 1907. Price, 15 cents.

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19J

U. S. DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 192.

B. T. GALLOWAY, Chief of Bureau.

DROUGHT RESISTANCE OF THE OLIVE
IN THE SOUTHWESTERN STATES.

BY

SILAS C. MASON,

Arboricultueist, Crop Physiology and

Breeding Investigations.

Issued January 17, 1911.

WASHINGTON:

GOVERNMENT PRINTING OFFICE.
1911.

BULLETINS OF THE BUREAU OF PLANT INDUSTRY.

Thescientific and technical publications of the Bureau of Plant Industry, which was organized July 1,
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192 [Continued on page 3 of cover.]

U. S. DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 192.

B. T. GALLOWAY, Chief of Bureau.

DROUGHT RESISTANCE OF THE OLIVE
IN THE SOUTHWESTERN STATES.

BT

SILAS C. MASON,

Arboriculturist, Crop Physiology and
Breeding Investigations.

QHieo

^/v.

Issued January 17, 1911.

WASHINGTON:

GOVERNMENT PRINTING OFFICE.

1911 .

BUREAU OF PLANT INDUSTRY.

Chief of Bureau, Beverly T. Galloway.
Assistant Chief of Bureau, G. Harold Powell.
Editor, J. E. Rockwell.
Chief Clerk, James E. Jones.

Crop Physiology and Breeding Investigations.

SCIENTIFIC staff.

Walter T. Swingle, Physiologist in Charge.
S. C. Mason, Arboriculturist.
G. P. Rixford, Expert.
E. M. Savage, Assistant Plant Breeder.

Bruce Drummond, W. L. Flanery, E. W. Hudson, M. A. Downes, and Henry H. Boyle,
Assistants.
192

i

LETTER OF TRANSMITTAL.

U. S. Department of Agriculture,

Bureau of Plant Industry,

Office of the Chief,

Washington, D. C, July 30, 1910.

Sir: I have the honor to transmit herewith and to recommend
for piibhcation as Bidletin No. 192 of the special series of this
Bureau the accompanying manuscript, entitled ''Drought Resistance
of the Olive in the Southwestern States." This paper was prepared
by Prof. Silas C. Mason, Arboriculturist in Crop Physiology and
Breeding Investigations, and has been submitted by Mr. Walter T.
Swingle, Physiologist in Charge, with a view to its publication.

The data upon which the paper is based were obtained from the
study of olive plantations made in Arizona and California, started
under irrigation, but afterwards, through the failure of the water
supply, left to their fate.

While most fruit trees and vines planted under similar conditions
soon perished, the olive trees have survived and made considerable
growth, showing themselves to be true desert plants having marked
drought-resistant characters.

So strong is this characteristic in the case of some of the varieties
of olives grown for oil that it is considered desirable to investigate
the possibility of olive culture for oil production in those areas in
the Southwest having favorable conditions as to temperature and
soil, but with a rainfall not heretofore believed to be sufficient for
crop production. At the same time those who desire to experiment
should be warned not to plant extensively until the possibilities of
fruit ])roduction in an}^ particular region have been thoroughly
investigated.

With the enactment and enforcement of the Pure Food Law the
production of olive oil in the Western States is now on a much
different footing from that of a few years ago. Where large ({uan-
tities of cheap adulterants and substitutes were then sold as pure
olive oil, now the olive grower has a market for his prochict on its
merits. With the better prices now prevailing, there seems to be
encouragement for a considerable extension of the oil-olive industry.
192 3

4 LETTER OF TRANSMITTAL.

Mr, Thomas H. Kearney has pubhshed a bulletin in this series,

entitled "Dry-Land Olive Culture in Northern Africa," describing

the methods pursued in dry-land olive culture in southern Tunis,

methods which are now being tested in this country by Prof. S. C.

Mason and Mr. Kearney in cooperation.

Respectfully, G. H. Powell,

Acting Chief of Bureau.
Hon. James Wilson,

Secretary of Agriculture.

192

i

CONTENTS.

Page.

Introduction 9

Dry-land olive investigations 10

Examples of drought resistance of the olive in the United States 10

An abandoned olive grove at Casa Grande, Ariz 10

The Bogart-Degolia olive grove 13

Dry-land olive grove near Florence, Ariz 15

Dry-land olive trees near Phoenix, Ariz 16

The Pope olive plantation, near Palm Springs, Cal 17

Description 17

Climate of Palm Springs 18

Soil at Palm Springs 20

History of the grove 23

Present condition of the grove 24

Olive root systems adapted to utilize limited rainfall 27

Moisture economy aided by the structure of the olive leaf and stem 30

Successful dry-land olive culture in California 31

Area of possible dry-land olive culture in the United States 34

Area limited by the minimum temperature 34

Area limited by heat requirements 37

Area limited by rainfall 41

Summary 42

APPENDIX.

Anatomical structure of the olive {Olea europea), by Dr. Theo. Holm 47

Root structure of the olive 47

Leaf and stem structure of the olive 49

Description of plates 56

Index 57

192 5

ILLUSTRATIONS.

PLATES.

Page.
Plate I. Fi^. 1. — One of the larger olive trees on the Bogart-Degolia planta-
tion, near Casa Grande, Ariz. Fig. 2. — Olive tree at" Las Palmas,"

near Phoenix, Ariz., after six years of neglect 56

II. Fig. 1. — View in the olive grove at Florence, Ariz., showing dead
apricot and almond trees in contrast with flourishing olives after
six years without irrigation. Fig. 2. — Interior view in the grove
shown in figure 1, the foliage, on account of crowding, having
become thinner than that of the outer row 56

III. Fig. 1. — View in the Pope olive plantation, near Palm Springs, Cal.,

after six years of neglect. Fig. 2. — One of the larger trees in the
Pope olive plantation, showing the low habit of growth of the
trees 56

IV. Fig. 1. — Characteristic burl at the base of an olive tree on the Pope

plantation, near Palm Springs, Cal. Fig. 2. — Feeding rootlets

^-^ from 6 inches in depth, on the Pope olive plantation 56

V. Fig. 1. — Cross section of the midrib of the leaf of Oleaeuropea (Mis-
sion variety) . Fig. 2 . — Cross section of one of the apical interned es

of the stem of Olea europea (Mission variety) 56

VI. Fig. 1. — View in a 500-acre olive plantation near La Mirada, Cal.
Fig. 2. — View in a different part of the plantation shown in
figure 1, where the trees have been thinned by removing alternate
diagonal rows 56

TEXT FIGURES.

Fig. 1. Map showing the points in Arizona and southern California where dry-
land olive growth was studied 11

2. Diagram showing the mean monthly rainfall at Casa Grande, Maricopa,

Phoenix, and Mesa, Ariz., as presented in Table 1 12

3. Diagram showing the mean monthly relative humidity at Phoenix,

Ariz., as presented in Table II 12

4. Diagram showing the mean monthly rainfall at Palm Springs station,

Cal., as presented in Table III 19

5. Diagram showing the relative percentages of fine gravel, coarse sand,

medium sand, fine sand, very fine sand, silt, and clay in dry-land
olive plantations in northern Africa and in Arizona and southern
California 21

6. Olive trees which have died through competition with a row of cotton-

wood trees on the Pope olive plantation, near Palm Springs, Cal 26

7. Diagram showing the distribution of superficial roots and deep roots of

a Manzanillo olive tree on the Pojx' olive plantation 29

192 7

8 ILLUSTRATIONS.

Page.
Fig . 8 . Diagram showing the root system of a typical dry-land olive tree on the
Pope olive plantation, showing the position and distribution of the

roots in the soil 29

9. Diagram showing the annual rainfall at Los Angeles, Cal., as presented

in Table VI - ----- 31

10. Diagram showing the monthly means and summation of heat units of

places in the olive-growing regions, illustrating the seasonal activ-
ity and heat requirements of the olive, arranged from Table IX 40

11. Transverse section of a young lateral root of the third order of an olive

tree from Palm Springs, Cal., showing a very hairy epidermis and
cortex '* '

12. Inner portion of the same transverse section of the olive root shown in

figure 11 "^^

13. Transverse section of a lateral root of the first or second order of an

olive tree, showing the development of phellogen and cork 48

14. The same transverse section shown in figure 13 of the root of an olive

tree, showing the development of a secondary cortex and paren-
chyma rays from the cambial strata 48

15. Diagram of the root of an olive tree, showing the general arrangement

of tissues described in figures 11 to 14, inclusive 48

16. One of the peltate hairs from the surface of an olive leaf - - 50

17. A sunken stoma and the uneven dorsal surface of an olive leaf 50

18. Ventral face of an olive leaf, showing the thickened walls of epidermal

cells and palisade cells 51

19. Pneumatic tissue of the dorsal side of a blade traversed by stereome

cells ^1

20. Development of cork layers in the cortex of an olive stem 52

192

i

J

B. p. I.— 596.

DROUGHT RESISTANCE OF THE OLIVE IN
THE SOUTHWESTERN STATES.

INTRODUCTION.

Olive culture in the United States has passed through many vicis-
situdes. Hence, for the fullest knowledge of this industry to-day
we should study not only those cases where olive planting has been
a financial success, but the frequent instances where a more or less
successful growth of olive trees has been obtained without a remuner-
ative production of fruit. The olive tree may maintain life and even
make considerable growth under conditions of drought and heat so
severe that only the most hardy types of desert trees are able to survive
them, yet the margin between such a purely vegetative growth and the
production of fruit in remunerative quantities may be a very wide
one, so wide that to invest money in the planting and care of olive
trees on a commercial scale under such conditions would be sheer

folly.

Again, it may occur that one olive grove is producing bountifully
while another near by, under substantially the same conditions as to
temperature, rainfall, and soil may give but a scant return. Here the
choice of varieties, the distance of planting, and the methods of cul-
ture and pruning, factors all within the control of the grower, may be
quite sufficient to explain the difference between success and failure.

In fact with any given example of olive trees which do not fruit,
especially if they are distant from productive trees for comparison,
only the closest study and thorough experimentation can determine
how narrow the margin may be between thpir present conditions and
those of profitable fruit production.

When any plant of economic value is found to possess great ability
to resist drought or heat that fact in itself becomes a matter worth
close investigation. How does it obtain its supply of moisture ? By
means of deeply penetrating roots or of superficial roots exploring
great areas? Has it some provision for the storage of moisture in
time of surplus? Does it possess peculiarities of stem or leaf struc-
ture by which the small moisture su])ply is conserved to the utmost
and the living cells insulatetl and protected in the most effective
192 9

10 DROUGHT KESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

manner against the desiccating effects of dry air and intense heat?
We may even inquire whether its cycle of growth in rehition to the
seasons does not undergo an adjustment adapting itself to periods of
drought and rainfall.

The present bulletin is an attempt to answer such questions in
relation to the olive, and the material upon which it is based has been
furnished by a number of plantations of olives made in the more arid
parts of Arizona and California, where through failure of the irriga-
tion systems the trees were thrown on their own resources. It is
noteworthy that in all such cases where besides olives other fruit
trees were planted, few of the olives died and almost without excep-
tion all other fruit trees perished.

DRY-LAND OLIVE INVESTIGATIONS.

In the writer's study of the possibilities in dry-land tree growth in
southern Arizona and southern California his attention has been
called to several cases of abandoned plantations where, along with
other fruit and ornamental trees, considerable blocks of olives had been
planted. With the failure of the irrigation canals and the consequent
cessation of care and culture of the trees, almost all kinds died.

The survival of the olives, and not only their survival but continued
growth and luxuriant appearance, was so notable a feature as to
attract the attention of observing ranchmen of the vicinity, for it must
be kept in mind that these were localities where irrigation was not
simply a convenience, but an absolute necessity to the growing of
every crop at present known to them.

The examples given below showing not the results of careful test
and experimentation but results obtained unwittingly and in the face
of disaster seem worthy of careful record when studied in the light
of the remarkable dry-land olive culture in Tunis, for the first time
brought to the attention of this country by Mr. Thomas H. Kearney,*^
of the Bureau of Plant Industry.

EXAMPLES OF DROUGHT RESISTANCE OF THE OLIVE IN THE

UNITED STATES.

AN ABANDONED O^IVE GROVE AT CASA GRANDE, ARIZ.

The first of the abandoned plantations noted was that known as
the Bogart-Degoha ranch, 2 miles south of Casa Grande station in
Pinal County, Ariz. (See fig. 1.) The altitude of the station is
about 1,396 feet, and the olive orchard is only a few feet higher.
The mean annual temperature for the twenty-three years recorded is
72° F., and the average annual rainfall is 6.88 inches.

"Roo " Dry-land Olive Ciiltnro in Northern Afrira," Bnllotin 12,5, Bureau of Plant
Industry, U. S. Dept. of Agriculture, 1908.
192

EXAMPLES OF DEOUGHT RESISTANCE.

11

Table I. — Average rainfall by months and annual average for Casa Grande, Phoenix,
Maricopa, and Mesa, Ariz., for the years from 1897 to 1908, inclusive.^'

Station.

Jan.

Feb.

Mar.

Apr.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

Year.

Casa Grande

In.

61.04

1.10

.78

1.11

In.

0. 80
.90
.72

1.02

In.
60. 36
.51
.38
.80

In.

0.25
.51
.33
.49

In.

0.03
.05
.04
.08

In.

60.19
.11
.16
.12

In.

60.97

1.03

.91

.83

In.

1.03
.98
.83

1.31

In.

60.37
.98
.52
.59

In.
60.13
.32
.25
.35

In.

0.88
.89
.72
.861

In.

0.78
.72
.78
.01

In.

6 6. 88

Phoenix

8.11

Maricopa

6.41

Mesa

8.60

Average

1.01

0.87

0.51

0.39

0.05

0.14

0.93

1.04

0.62

0.26

0.84

0.82

7.52

a The figures of this table were kindly furnished by Mr. L. N. Jesunofsky, section director, Weather
Bureau, Phoenix, Ariz.

6 Ttiese means were obtained by substituting the mean of the month specified in places where the record
was wanting.

Figure 2 shows graj^hically the average rainfall by months for Casa
Grande, Ariz., and adjacent stations, from 1897 to 1908, inclusive.
The two periods of greater rainfall each year, one culminating in

Soefre^fr ar/

Fig. 1.— Map showing the points in Arizona and southern California where dry-land olive growth was

studied.

August and one in November, with ^May aiul June nearly rainless,
are characteristic of the region.

The range of temperature during the year is from a minimum of
25° or 28° F., with occasional years as low as 17°, to a maximum of
117° to 122° F. The mean relative humidity recorded for Phoenix
in Table II and grai)hically illustrated in figure 3 wall not be far
from correct for the Casa Grande region.

Table II. — Mean monthly and mean annual relative humidity of Phoenix, Ariz., for

the years 1905, 1906, and 1907.

Year.

Jan.

Feb.

Mar.

Apr.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

Year.

1905

P.ct.
61
50
66

P.ct.
71

60

58

P.ct.
67
48
51

P.ct.
58
40
30

P.ct.
35
31

28

P.ct.
25
20
24

P.ct.
29
34
36

P. ct.
42

47
44

P.ct.
41
30
36

P.ct.

40
31
55

P.ct.
65
45
55

P.ct.
59
65
42

P.ct.
49

1906

42

1907

44

192

12 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

I

' 1

nil

Fig. 2.— Diagram showing the mean monthly rainfall
at Casa Grande, Maricopa, Phoenix, and Mesa, Ariz.,
as presented in Table I.

The country around Casa Grande is a wide plain, through the
level of which the mountains appear to be thrust up, so abruptly
do the scattering groups and single low peaks break the surface.

These mountains are largely
composed of a soft, rapidly dis-
integrating granite, with much
feldspar in its composition, and
their decay determines the char-
acter of the soil, which is coarse
and gravelly around the moun-
tain base, sandy with more of
clay a little farther awa}^, and
of a stiff clay nature mingled
with bars of sand and gravel
along the drainage courses,
scarcely as 3^et marked as stream
channels, which serve to carry
away the run-off from the occa-
sional torrential rains so char-
acteristic of the region.

The most important of these
water courses, sometimes digni-
fied on the maps by being called the Santa Cruz River, is locally given
the more appropriate name "Santa Cruz Wash." While along its
upper course, from the Mexican boundary down to Tucson, there is
a pretty well-marked channel and a
more or less continuous flow of water,
in the neighborhood of Casa Grande a
slightly cut channel, a broad, well-
marked flood area, and a still broader
belt of mesquite growth mark the course
of the so-called river.

The popular idea that there is a
strong underflow of water the entire
length of this valley is given support by
the heavy belt of mesquite which occurs
with more or less regularity along the
course. This tree is well known through-
out the desert regions of the South-
west as possessing a remarkable root
system, able to penetrate to water-
bearing strata at depths of 30 to 50
feet. The further fact that the railroad wells along the line of
the Southern Pacific Company, particularly those at ]\Iaricopa
and Casa Grande, 2 or 3 miles away from the main channel, afford

192

1 /«=£>? cvr/v7- 1

I 1 1 1 1 1

1 1 i 1 1 1 ;

1 1 1 1 1 rj

■

- — 1 1 1— — 1

I

1 1 1

/V«4>fH^H^HV^H

1

-^^^'^flHHHB

'^'^ *^ Hl^HH^HHH

I

.s-iT/^^rMH^BJ^HH^H

1 1 1 1 1

1 1 1 \ 1

Fig. 3.— Diagram showing the mean
monthly relative humidity at Phoenix,
Ariz., as presented in Table II.

EXAMPLES OF DROUGHT RESISTANCE. 13

an abundant flow of water from deep borings, in which the water
rises to within 40 to 50 feet of the surface, seems to confirm the
impression.

The ranch of which the olive orchard forms a part Hes fully 3
miles south of the main Santa Cruz channel, with a gentle slope
toward it. A heavy mesquite growth had first to be removed as a
preparation for planting, and much growth of the same nature is
still to be found adjacent, indicating the presence of a water supply
at a depth of 30 to 50 feet. The soil contains a large percentage of
coarse granitic sand, but with enough clay to give it considerable
body and cause it to bake when dry. (See Tables IV and V.)

THE BOGART-DEGOLIA OLIVE GROVE.

According to the best testimony available, the Bogart-Degolia
ranch was planted in 1S93. It was at the time of the highest pros-
perity of the so-called Florence canal, which took water from the
Gila River near the town of Florence. About 20 acres of the ranch
were set to Muscat and Thompson seedless grapes, figs, apricots,
prunes, and olives, there being perhaps 5 acres of olives. The sup-
ply of water, while never abundant, was adequate for several years,
and the enterprise gave every promise of success.

Owing to the partial failure of the water for the past seven or
eio-ht vears, the trees have had no water save the rainfall and a little
local run-off that the otherwise dry ditches carried to the orchard.

We have no record of the exact order in which the trees began to
perish. When examined in March, 1907, all the trees planted were
dead except the olives, a few Arizona ash {Fraxinus velutina) which
had been set along the main ditch where they could profit by the
run-off which it could collect, and a few fig trees which still sent
feeble sprouts from the base. Appearances would indicate, however,
that the apricots and prunes were the first to succumb, followed by

the figs.

After the place was deserted, cattle and horses dependent on the
scanty desert herbage broke into the inclosure and attacked the
olive trees, browsing off all of the tender growth within reach. This
fact in itself bears testimony to the scantiness of forage on this plain,
for of all the forms of vegetation brt)Ught forward as forage jjlants
the olive has not so far been considered in the United States." Many
of these trees were browsed and broken till mere prongs and stubs,
3 or 4 feet high, were all that was left of theuL None of the trees
seem to have been pruned from the first, and the greater number of
them had formed several divergent stems from the ground. It was

a Mr. Thomas H. Kearney states that during dry years in Algeria branches cut
from olive trees are a regular forage supply. See Bulletin 80, Bureau of Plant Industry,
U. S. Dept. of Agriculture, p. 80.
192

14 DROUGHT EESISTANCE OF OLIVE IN SOUTHWESTEBN STATES.

usually where the outer stems had formed a sufficient barrier against
the stock that the central ones had attained an adequate growth to
enable them to resist attack. Man}^ of these have reached a height
of 12 to 15 feet, and a few exceptionally strong specimens are 18 to
20 feet high. (See PI. I, fig. 1.)

The foliage is a dark, luxuriant green, and vigorous new growth is
being made, even on those trees that have been most severely cropped
back by cattle. The whole plantation is a notable landmark on the
desert plain and can be seen for a long distance. In fact, unculti-
vated and abandoned to struggle for itself, the olive has made a
winning fight in fair competition with the mesquite of the surround-
ing desert, even though it has lacked the thorny defense against
grazing animals which nature has supplied to the desert tree.

The uniform distance in setting out this entire plantation was in
squares 24 feet apart. This would prove to be rather too close
planting even in an orchard having an abundant supply of water,
but where the supply is as scant as this plain affords experience has
shown that this spacing, which provides for 75 trees to the acre, is
much too close. The luxuriant growth of a portion of these trees
was doubtless made possible by the weakened competition of those
closely cropped by stock. The olive tree has the ability to produce
a system of shallow roots, fully occupying the ground for a wide
radius around each tree. But a few 3 ears are needed for a tree to
completely take possession of the soil over a radius of 12 feet, after
which the struggle must begin with neighboring trees for the avail-
able moisture.

A detailed study of the roots of a typical tree was made — a tree
with a trunk diameter of only 5 inches, enlarged just below the sur-
face of the ground into a burl 12 inches in diameter and 14 inches
in depth, from which radiated 12 roots from a half inch to 2 inches
in diameter. Some of these roots had a length of 12 to 14 feet. So
numerous were the branches and small feeding rootlets originating
from these roots that the soil from a depth of 2 or 3 inches to more
than a foot was filled with them.

The description of "Olive root systems" in this bulletin will afford
details applicable to all of these plantations.

At the remote areas penetrated by branches from the large roots
the ground was contested by feeding roots from the adjacent trees,
so that it was hardly possible to turn up a shovelful of earth in the
orchard without finding evidence of this reaching out for moisture.
Yet there was no taproot and no penetrating to great depths for
water, as is so characteristic of the mesquite, which had been the
natural occupant of this land. It was a most complete and perfect
system for appropriating the moisture in the first 15 or 18 inches of
the soil, just that which would be penetrated by the normal rainfall.

192

EXAMPLES OF DROUGHT RESISTANCE. 15

The soil, greatly deficient in humus, contains clay enough to make
it very hard when dry, and the tramping of grazing stock still further
compacted the surface, preventing the ready absorbing of water
when a rainfall came. Application of the now well-known principles
of thorough cultivation and light furrowing across the slope to secure
water storage and the retarding of evaporation by a dust mulch
would have aided these trees greatly in utilizing the rain which fell.

DRY-LAND OLIVE GROVE NEAR FLORENCE, ARIZ.

Not far from the Casa Grande and Florence road, in the valley of
the Gila River and about 5 miles southwest of Florence (see map,
fig. 1), a ranch was developed and a plantation of olives and other
fruits was made, probabl}^ at about the same time as that at Casa
Grande. An area of about 8 acres was set in olives, the trees being
arranged in squares 20 feet apart each way. This tract has been
kept securely fenced, so that no damage from live stock has occurred.
From the scant information that can be gathered these trees have
received no irrigation for six years.

The soil is a much stiffer clay than that at Casa Grande. A well
near the orchard, now caved in, shows no water for a depth of more
than 40 feet. An inspection of this grove shows that while possibly
5 per cent of the original setting of trees failed to grow, but a very
few died later. The average height of these trees is about 20 feet.
A majority of them grow in the form of stools, sending out several
minor stems from near the ground. Some single trunks from 8 to
12 inches in diameter were noted. The formation of a much en-
larged burl at the surface of the ground was a very common feature.

A most significant fact was that the trees around the borders of
the grove were much larger and of more vigorous and healthy growth
than those where there was a perfect stand in the interior. While
few of the interior trees are dying, the scantier and less healthy foliage
and more slender growth of the branches all testify to the severity
of the struggle for moisture which is taking place. (See PI. II, fig. 2.)

No systematic study of the root development was made, but a
number of holes dug in various parts of the grove showed that, as in
the Casa Grande grove, the extent of roots was such as to occuj^y
the entire area, fine rootlets being disclosed wherever the soil was
turned. Even where missing trees gave a diagonal distance of more
than 45 feet between those standing, the roots hatl extended so as to
occupy this space.

A most significant fact concerning this planting is shown in Plate

II, from photographs taken in March, 1909. A blo(^k of about 3

acres of apricots and almonds ])lanted by the side of the olives is

shown in Plate II, figure 1, on the left. The trees had made an

57054°— Bui. 192—11 2

16 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

excellent growth, but with the failure of the water every one of them
has died. On the right are seen the olive trees still making a good
growth. A few pomegranate bushes and pepper trees planted in the
dooryard adjacent to the olives, while nearly all living, have appar-
ently suffered more seriously from drought than the olives.

DRY-LAND OLIVE TREES NEAR PHOENIX, ARIZ."

A few miles northeast of Phoenix, Ariz., a tract of land was laid off
into a sort of residence park under the name of "Las Palmas."''
Numerous avenues and drives were planted with Canary Island
palms, pepper trees, and other ornamentals, and at the same time a
considerable number of olive trees was set out, a row along the south
side of the southeast quarter being half a mile long. Owing to diffi-
culties about the water supply, cultivation and care ceased over all
but a small part of the tract, so that for the past six years no irriga-
tion has been given the olives and peppers on the south side of the
section and only a small amount to some of the palms.

The soil here, though gravelly, is much richer in clay and fine silt
than that of the Casa Grande tract. This portion of section 22 has
for several years been heavily pastured by horses, cattle, and sheep,
the trampling of this stock being sufficient to render the ground
around the row of olives smooth and compact, so that much of the
rainfall would be turned off instead of being caught and allowed to
percolate to the roots. A much better supply of forage seems to have
prevented the stock in this pasture from browsing the olives as
severely as was done at Casa Grande, though apparently sheep have
fed off the leaves and small twigs to a height of about 4 feet.

We find this to be a case of growth under decidedly adverse condi-
tions, though not the most extreme. The row of olive trees along the
south side of the section is uneven in growth, but many are 12 to
15 feet high, with trunks from 5 to 7 inches in diameter. Here,
as in other droughty situations, the olive has a strong tendency to
put out sprouts from near the base, thus protecting the trunk from
the heat of the sun. This universal habit of olive trees in dry locali-
ties, even those that have been headed high enough to expose the
trunk, points clearly to the desirability of a method of pruning which
will provide a low, spreading head, thoroughly protecting the trunk
and main branches.

That several of the trees in this south row should have fruited in
1907 in the face of such privation and neglect, though producing only
a light crop, is strong evidence of the hardiness and drought resistance
of the olive.

« See map, figure 1. b Comprising section 22, in township 2 north, range 3 east.
192

EXAMPLES OF DROUGHT RESISTANCE. 17

In the northern portion of the ranch oHve trees which had received
a httle irrigation and less tramphng and hardening of the ground
produced fair crops of fruit, thus demonstrating that a small differ-
ence in conditions may be sufficient to decide between a mere holding
on to life and a fair commercial success. The climatic conditions
indicated in Table I for Phoenix will be a close approximation to
those prevailing at this place. Plate I, figure 2, shows a character-
istic tree of the south row in fruit.

THE POPE OLIVE PLANTATION, NEAR PALM SPRINGS, CAL.

DESCRIPTION.

In traveling over the Southern Pacific Railway from Los Angeles
to the east, one leaves the orange groves of Colton and Redlands to
ascend into a cooler region, an altitude of nearly 3,000 feet being
reached in the San Gorgonio Pass. Here, around Beaumont and
Banning, are flourishing orchards of prunes, peaches, and apricots,
watered from the perpetual snows of the San Bernardino Range, and
extensive barley fields moistened by the winter rains. A descent of
2,000 feet in 30 miles to Palm Springs station then brings one seem-
ingly into another country. A sparse growth of desert shrubs and
herbs in torrent-washed gravel and among bowlders replaces the
orchards and harvest fields, and instead of the refreshing breezes
from the snow-capped peaks there is much of the time a sand-laden
gale blowing so steadily down the valley that all the desert shrubs lie
prostrate and the drift of sand to the leeward of each makes it seem
to be marking a nameless grave. Just ahead lies a low range of hills,
their original rock formation barely suggested beneath the mantle of
sand that centuries of winds have heaped upon them. No landscape
could be in more striking contrast with that left behind at Colton and
Beaumont.

Taking the trail to the southward from Palm Springs station for a
few miles carries one out of the sweep of the winds to a sheltered sec-
tion containing the picturesque little village of Palm Springs at the
site of the old Agua Caliente. (See map, fig. 1.) The Mission
Indian village lies on the east side of ''Inclian avenue" and a little
group of homes of the white settlers on the west, all nestling under
the shelter of the towering San Jacinto Mountain, whose two peaks,
San Jacinto and Cornell, are among the highest in southern Cali-
fornia. From a jagged rent in the eastern base of the mountain
issues an ice-cold stream of water, a brawling torrent when the
mountain showers are heavy or the snows are melting rapidly, but
sinking to a tiny rivulet at the end of the long desert summer, barely
sustaining life in the little oasis dependent upon it. In fact, during

192

18 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

a series of extremely dry years it has happened that the flow of 9 or
10 miner's inches, or about 120 gaUons, per minute from the hot
spring pool has been all there was to sustain plant or animal life for
months at a time.

A little way out on the desert one notices rows of pepper trees
(Schiniis moUe), their rich, dark green in sharp contrast with the
desert herbs and shrubs, while a nearer approach shows, perhaps, a
half-dismantled house and a broken fence inclosing a small field.
Gaunt rows of cottonwood trees, a few still keeping up the struggle,
the greater part standing stiff and white, seem ghostlike sentinels
keeping watch along the line of a ditch that has long since ceased to
convey the life-giving water. Acres of grapevine stumps, blocks of
dead a})ricot trees, skeleton branches of bleaching fig trees, a few
green sprouts struggling from their bases — all give eloquent testimony
to the energy and capital invested in the Palmdale settlement in 1889,
when the granite-lined canal brought a supply of water from the
Whitewater River across 7 miles of blowing sand to irrigate this
sheltered spot at the foot of the San Jacinto Range.^

In striking contrast to the impression of desolation offered by the
majority of these abandoned fields is that of a tract lying a mile
northeast of Palm Springs, Cal.,'' where, if one ascends to a little
elevation above the plain, the check rows in dark, rich green of an
olive plantation of 26 acres shows in striking contrast to the brownish
green of the creosote bush (Covillea tridenta), which forms the natural
growth. Here in 1891 was set an olive grove of approximately 3,000
trees, together with some 6 or 7 acres of figs. (See PI. Ill, fig. 1.)

CLIMATE OF PALM SPRINGS.

Palm Springs has the typical desert climate, modified somewhat
by its proximity to the San Jacinto Range, which cuts off the fierce
sweep of the winds which come down through the San Gorgonio Pass
and spread out over the country above the Salton Sea. The summer's
heat is intense and prolonged, maximum temperatures of 100° F. and
over being leached every month from May to September, inclusive,
and occasionally even in April and October. The absolute yearly
maximum for the ten years from 1897 to 1906, inclusive, ranges from
1 13° to 122° F., only 1904 failing to reach 1 16° F. The lowest recorded
winter temperature is 28°, but more often 32° F. is the record, and
sometimes winters ])ass with scarcely a trace of frost. Although
within 12 miles of the snow-capped San Jacinto peaks, the mean

a Since the studies herein described were made, much of the canal stock and a con-
siderable acreage of land have been acquired by persons who have repaired the canal
and begun again the approi)riation of water from the Whitewater River.

b A portion of section 11, in township 4 south, range 4 east.
192

EXAMPLES or DROUGHT RESISTANCE.

19

annual precipitation is a scant 3^ inches, with a total of only 0.70
inch for 1903 and a maximum of 9.36 inches for 1905. (See Table III.)

Scant as this rainfall is it nearly all occurs in the six months
from October to March, inclusive. During the six summer months
when a temperature of 100° F. is reached almost daily there is
scarcely a trace of rain. (See
fig. 4.) That any vegetation
should be able to pass through
this terrible period of heat and
drought seems beyond belief t o
one accustomed to the behavior
of plant growths of the regions
having abundant rainfall; yet
many species of shrubs and
three species of trees are native
in these hot sands.

That the olive, whose beauti-
ful groves are typical of the most

favored portions of France and Italy, should be able to survive and
even successfully compete with these desert shrubs in their own
habitat, when planted among them and then abandoned, gives us a
new insight into the real character of this tree that makes it worthy
of careful study.

Table HI.— Maximum and viinimum temperatures and preci-pitation at Palm Springs
station, four miles north of the Pope olive plantation, California, elevation 584 feet, for
the years 1897 to 1907, inclusive.

MAXIMUM TEMPERATURE (DEGREES FAHRENHEIT).

ft

1

1

n
1 1
1 1

n

1 1
1 1

t

n m

m ■

\

5 T

1

1

V

^

1

1

^

Fig. 4.— Diagram showing the mean monthly rain-
fall at I'alm Springs station, Gal., as presented in
Table III.

Year.

Jan.

Feb.

Mar.

Apr.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

Annual.

1897

68
73
82
81
78
98
70
78
72
70
74

74
88
84
86
98
105
72
86
70

"'84'

83
95
84
97
96
105
85
92
81
88
91

103

108

102

94

95

98

97

106

78

101

100

108
102

92
106

98
101
111
103
110
102

95

Ill
110
116
111
118
121
112
112
110
112
115

120
116
116
118
111
110
117
113
122
116
118

118
115
114
110
114
106
110
111
115
116

104
112
113
107
106
112
112
107
110
106
102

97

102

96

104

98

95

98

102

98

104

100

89
92
90
90
90
85
88
96
82
94
88

78
78
86
78
82
75
81
81
74
75
78

120
116
110
118
118
121
117
113
122
116

1898

1899

1900

1901

1902

1903

1904

190.5

1906

1907

MINIMUM TEMPERATURE (DEGREES FAHRENHEIT).

1897.
1898.
1899.
1900.
1901.
1902.
1903.
1904.
1905.
1906.
1907.

38
30
30
34
30
32
40
32
45
33
30

32

48
28
38
44
30
32
39
28

'■io'

37

42
46
50
50
42
4(i
49
50
42
42

40
54
56
42
58
50
50
53
46
50
55

39

58
60
52
04
62
54
53
50
58

65
70
66
60
61
59
60
69
60
62
70

77
78
8.5
69
75
66
05
75
75
84
72

81
78
70
70
80
68
68
79
80
70

68
64
70
64
05
(iO
58
61
70
62
60

55
62
50
54

(i5

m

58
62
60
47
60

42
42
50
48
47
.35
50
56
40
32
46

30
32
32
44
30
40
34
48
30
40
35

30
32

28
34
30
30
32
32
28

'30

192

20 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

Table III. — Maximum and minimum temperatures and precipitation at Palm Springs

station — Continued.
PRECIPITATION (INCHES).

Year.

Jan.

Feb.

Mar.

Apr.

May.

T.

0.48

Jiiiie.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

Annual.

1897

0.12

3.50

T.

3.95

'".'47"

0.60

.50

.70

'i.'ee'

3.05
1.27

0.50

T.

.20

.15

T.

0.62

1.00

.10

T.

0.05

1.29

.10
/

1.64

0.50

T.

.70

T.

1.11

.70

1.09

.70

2.86

.70

.56

T.

1.09

1KQR

1899

1.21

.80

T.

.50

T.

2.16

.46

1.27

5.31

1900

2 09

1901

3.50

1902

2.90

1903

.70

1904

1905

9.36

1906

1907

T.=trace.
SOIL AT PALM SPRINGS.

The soil of the oUve orchard is typical of this district. The rock
formation is coarse sandstone and granite. The southern face of the
mountains is broken by canyons of various widths and depths, origi-
nating as rents and fissures in the uplifted rock, but enlarged by the
erosion of the mountain torrents, which were apparently during
glacial times of vastly greater volume than at present. The result
has been an enormous talus of water-worn liowlders from each of the
main canyons extending out into the basin to an unknown distance
and depth and spreading laterally along the mountain base. Over
this is a varying depth of coarse sandy and gravelly soil, in places
mixed with a considerable quantity of finer material from the sorting
action of wind and water. Several square miles in the Palm Springs
and Palmdale region have thus a fair quality of sandy soil, which is
lacking in sufficient clay or fine binding material and because of the
scanty rainfall and sparse vegetation is low in organic matter. Judg-
ing from the quantity of feldspar in the original granitic rock, there
is doubtless a good deal of available potash in this soil.

On the particular 40 acres in the olive orchard there is rather less
of the finer material in the soil than in that of the Indian reservation
lands adjoining on the south. Layers of coarse gravel and cobble-
stones are often encountered at depths of 3 to 4 feet. The longest
winter rains sink so quickly into the soil that there is no trace of
stickiness or mud on the following day.

Table IV. — Mechanical analyses of soils frovi olive orchards at Casa Grande, Ariz.,
and Pcdm Springs, Cal., made by the Bureau of Soils, U. S. Department of Agricul-
ture, from samples collected by Mr. S. C. Mason.

Locality.

Depth

taken.

Fine

gravel,

2tol

mm.

Coarse
sand,

1 to 0.5
mm.

Me-
dium
sand,
0.5 to

0.25
mm.

Fine

sand,

0.25 to

0.1 mm.

Very
fine

sand,

0.1 to
0.05

mm.

Silt,

0.05 to

0.005

mm.

Clav,
0.005 to
mm.

Casa Grande, .Vriz

Inches.
Oto 6
6 to 12

12 to 18
Oto 6
6 to 12

12 to 18

P.ct.
4.0
3.7
4.4
4.0
4.0
3.4

P.ct.
15.1
13.5
14.0
15.2
15.0
14.1

P.ct.
10.4
9.1
9.4
42.0
15.4
14.0

P.ct.
25.0
26.0
2.5.0
17.7
43.4
40.2

P.ct.
11.1
10.0
9.1
13.2
1.3.1
14.9

P.ct.
27.1
32.3
32.1
7.2
8.0
11.3

P.ct.
8.0

Do

,5.0

Do

6.6

Palm Springs, Cal

.8

Do

.9

Do

1.6

192

EXAMPLES OF DKOUGHT RESISTANCE.

21

/

30

20

10

S FAX

OLIVE ORCHARD

OLIVE ORCHARD 20
MILES F ROM SFAX

■ ■ I I

S PAX

OLIVE ORCHARD

xll

1

f

> n:

^ 'o ^: «o ^. s ,

k- U ^ i< S (0 ^

?^-

ID "o 5" «d ;^

«) <o" ^. h i^.

Uj

v

rO/2 / INCHES DE£P

y \

^*.- ^ ^ k ^ <oji/ A- t> ^" V: S <o ^

/2 INCHES DEEP

/ <Z

z/

/3 TO Z^ /NCNES OE£P

50

^0

30

20

I

BOGART OLIVE GROVE

CASA GRANDE ARIZONA

nm

> \

^ "Q. < .
•< ^ i^ (0

\j

O TO 6 /A/Cf^ES DEEP

tTntpr

/ ^k- ^ ^ k ; ^ ^- <o o.

Ml

/

to" "o
.k C5

"9 (o I?:

^ k ^-

J

i^

o.

y

6 TO /2 WCf^ES OEEP

/2 TO /S //I/C//EJ- OEEP

60

5

^0

30

20

10

POPE OLIVE GROVE

PALM SPRINGS CALIFORNIA

zt

It

U

ill

tn

\ to

\

k-

I

^ ^

"\^

/

to- H !3'
\k ^ ^

b- 1^: s:
k-Jjo O
•\y

Ml

to- Id; 'q lo- {^^ .

/ \

to ^6 *^ ^-

M^. Cj ^ k- ^ «oO

A/-

y

O TO S /NCHES 0££P S TO /Z /A/CHES OEEP /Z TO /S /NC^ES DEEP

Fig. 5.— Diagram showing the relative percentages of fine gravel, coarse sand, medium sand, fine sand,
very fine sand, silt, and clay in dry-land olive plantations in northern Africa (Sfax) and in Arizona
and southern California.
192

22 DROUGHT RESISTANCE OE OLIVE IN SOUTHWESTERN STATES.

Table V. — Analyses for potash, phosphoric acid, calcium, and organic matter in soils
from olive orchards at Casa Grande, Ariz., and Palm Springs, Cal., made by the Bureau
of Soils, U. S. Department of Agriculture, from samples collected by Mr. S. C. Mason.

Locality.

Casa Grande, Ariz

Do

Do

Palm Springs, Cal

Do

Do

Depth
taken.

Inches.
Oto 6
6 to 12

12 to 18
Oto 6
G tol2

12 to 18

CaO.

Per cent.
1.18
.53
1.86
1.58
1.58
1.75

KtO.

Per cent.
0.98
1.00
1.00
.81
1.02

PjOs

Per cent.
0.03
.22
.32
.52
.38
.41

Organic
matter.

Per cent.
0.15
.46
.66
.19
.12
.17

Figure 5 shows in a graphic manner the resuUs of a mechanical
analysis of this soil by the Bureau of Soils, as presented in Table IV.
This is placed for comparison below a diagram showing the results
of a similar analysis of the soil from the Casa Grande olive grove and
one from the olive orchards of Sfax. '^ The small quantity of clay
and silt and the large proportion of medium and fine sand distinguish

« See "Dry-land Olive Culture in Northern Africa," by Thomas H. Kearney, Bulle-
tin 125, Bureau of Plant Industry, U. S. Dept. of Agriculture, 1908, pp. IS-l'J, as
follows :

Mechanical analyses of soil samples from the olive orchards ofSfax.

Locality.

Olive orchard, Sfax

Do

Do

Do

Olive orchard, 20 miles north of
Sfax

Me-

Very

Fine

Coarse

dium

Fine

fine

Silt,

Depth

gravel,

sand,

sand,

sand,

sand,

0.05 to

taken.

2 to 1

1 to 0.5

0.5 to

0.25 to

0.1 to

0.005

mm.

mm.

0.25
mm.

0.1 mm.

0.05
mm.

mm.

Inches.

P.ct.

P.ct.

P.ct.

P.ct.

P.ct.

P.ct.

Oto 12

0.2

4.3

7.1

24.1

20.9

14.1

13 to 24

.4

7.7

9.7

33.9

24.0

9.1

25 to 36

.5

7.9

10.3

34.3

24.6

7.1

Oto 12

.2

4.6

6.8

26.4

22.5

13.4

(a)

.3

2.7

3.3

14.9

27.0

22.9

Clay,
0.005 to
mm.

P.ct.
30.0
16.0
15.7
26.2

29.3

a Adhering to olive truncheons, probably about 12 inches.

Chemical analyses of a large number of samples of the Sfax olive soils by the chemist
of the Tunisian government show them to be very rich in lime (calcium carbonate),
of which there is an average of from 5 to 10 per cent. The potash content is also good,
the average being 0.1 to 0.2 per cent. On the other hand, they are rather poor in
nitrogen (0.03 to 0.05 per cent) and in phosphoric acid (0.04 to 0.05 per cent). Accord-
ing to Trabut, a high lime content is a very favorable factor in growing olives for oil
production, as olives produced in limestone regions are richer in oil and the oil is of
better quality then where the soils are deficient in this component. It should be
noted that while the nitrogen and phosphoric acid content of the vSfax soils would be
considered low for most crops, the high yields and good quality of the oil produced at
Sfax are sufficient evidence that the supply of these two elements of plant food must
be amply vsufficient for the requirements of the olive. This can perhaps be explained
by Ihe fact that the roots of this tree occupy so great an area of soil (one-seventh to
one-tenth acre) that, while the percentage of these elements to weight of soil is every-
where low, the total amount available to the roots is actually rather high.
192

EXAMPLES OF DROUGHT RESISTANCE. 23

this Palm Springs soil in a very marked way from that of the Casa
Grande. Both are in striking contrast with samples from the dry-
land olive district of Sfax, in northern Africa, described in Mr.
Kearney's bulletin previously referred to. The much higher per-
centage of clay in the Sfax samples gives a very distinct character to
that soil, which as it exists in nature impresses one as sandy, owing
doubtless to the clay and silt particles being cemented together.

In chemical composition these soils (Table V") show a striking
similarity in the lime content, having only one-eighth to one-fourth
as much of that element as is found at Sfax.

In the amount of potash the Casa Grande and Palm Springs sam-
ples are also very much alike, being five to ten times richer than the
Sfax samples. In the amount of phosphoric acid it is interesting to
note that the Palm Springs soil, though seemingly a desert sand,
contains more than twice as much of this important element as is
found in the Casa Grande samples. In the potash and phosphoric
acid contents either of these samples compares favorably with aver-
age agricultural soils ; for instance, with the soils of the famous Michi-
gan peach belt, ^ while in phosphoric acid the Palm Springs samples,
averaging 0.436 per cent for the entire 18 inches in depth, are ahead
of all but the very richest farm lands of the eastern United States.
This richness of desert soils in phosphoric acid and potash is espe-
cially advantageous to olive culture, as investigations by the Cali-
fornia Agricultural Experiment Station have shown that the olive
makes mucli higher demands upon the soil for these elements than
do grapes, plums, apricots, or oranges. •=

HISTORY OF THE GROVE.

As nearly as can be gathered the greater part of the Pope olive
orchard was set in 1890 and 1891. There was at that time an ade-
quate supply of water available from the Whitewater ditch, which
was conveyed to each block of land by box conduits. Along these
conduits and across the north side of the blocks rows of cottonwood
trees were set 20 feet apart. Their influence on the olive plantation
will be referred to later.

The olive trees were planted 21 feet apart on the hexagonal system,
giving 116 trees to the acre. For the first seven or eight 3'ears there
was a fair supply of water. No Bermuda grass or other serious weed
gained a foothold and the work of irrigating the trees was the chief

a From analyses by Mr. Joseph G. Smith, of the Bureau of Soils, U. S. Dept. of
Agriculture.

6 See Roberts, I. P., "The Fertility of the Land."

c Report of the Director of the California Agricultural Experiment Station, 1894-95,
p. 124.
192

24 DROUGHT KESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

labor. It can not be learned that during that time any fruit was
produced. A resident of Palm Springs who came there in 1896
recalls that they were "expecting the trees to come into bearing
the next year." About this time difficulties with the water supply
began, and as nearly as can be ascertained no irrigation at all has
been given the orchard since 1900.

PRESENT CONDITION OP THE GROVE.

The first fact with which one is impressed on seeing this plantation
is the small size of the trees considering their age. Some trees are
scarcely 4 feet high, and very few more than 7 or 8 feet. Taking
two average rows, the range in height was found to be from 41 inches
to 98 inches, the average for 50 trees being 63.5 inches. The high-
est tree in the 20-acre block was found to be 9 feet, while only 10
trees could be found measuring 8 feet and upward. (See PI. Ill,

fig. 2.)

It is to be noticed that on these trees the branches are retained

clear to the ground and that the breadth of the top exceeds the

height in almost every case, so that in the 50 trees examined only one

was found in which the height was greater than the breadth of top.

The average breadth for the two rows is 79.5 inches as against 63.5

inches of height. These tops, too, are much branched and very

compact. In nearly every case the trunk is concealed. A leafy

canopy protects the trunk and main branches from the dry air and

fierce heat of the desert sun.

In doing battle for their lives in the desert they have sliowTi their
ability to adapt themselves to desert methods of defense. The mes-
quite and paloverde,"^ the largest native trees, may attain a spread
of top of 40 or 60 feet with a height of only 20 or 30 feet. The
desert willow (Chilopsis) and the Dalea spinosa, two species somewhat
less resistant to drought and heat, attain a treelike size by throwing
out a defense of sprouts and low branches, or, failing in this, they are
apt to show scars of severe sun scalding.

The so-called "wild apricot" (Prunus fremontii) , venturmg out a
little way along the bowlder talus from the canyon's mouth, has a
top so densely branched, angled, and interlocked as to well merit the
name Emplectocladus, signifying interlocked branches, which now
applies to the whole subgenus to which it belongs.

Similar proportions of height to spread of top will be found in
nearly all of the characteristic desert shrubs, the effort seeming to be
to throw as much shade and insulation as possible around the trunk
and main branches.

o-Cercidium torreyanum (Wats.) Sargent.
192

EXAMPLES OF DROUGHT EESISTANCE. " 25

This purpose is accomplished most effectively and in the most
characteristic way of all by that typical desert tree, the majestic
palm ( Washingtonia filifera) , whose dying lower leaves suspended by
their long petioles form a dense thatch, completely insulating the
tall, columnar, branchless trunk against both the direct and reflected
heat of the sun and the drying winds. Wliere some vandal hand
does not apply a torch, this splendid protection is retained for many
years, perhaps for life.

It is probable that in the case of the olive, as well as of many native
desert plants, this low, spreading canopy of top serves another purpose.
Of the total precipitation for the year in these regions a considerable
proportion is in the form of small showers, so that the monthly record
will often be indicated by such fractions of an inch as 0.12, 0.09, 0.32,
0.06, trace, etc., these usually representing a single precipitation.
Such an amount falling upon the parched soil in the open is so soon
evaporated as to afford little aid to the thirsty plant. Arrested by
the leaves or fine branches and carried to the ground at the base of
the stem, it is so shaded and conserved as to be allowed to sink into
the surface soil, where a system of short, finely branched supei-ficial
roots is ready to appropriate it. In Plate IV, figure 2, such rootlets of
the olive tree are shown in natural size.

Inspection of the whole 26 acres of the plantation shows that sev-
eral varieties were set, just what they were being difficult to decide
with accuracy, no plat or planting list so far having been discovered.
The block in which the most trees are alive and in the best condition,
though not making the largest growth, has the dense, compact habit
and broad top most completely developed, and here any exposure of
trunk or main branches to the sun is hard to find. These trees are
noticeable for the complete absence of any sun scald on the bark.

The northern seventeen rows of this block are ranker in growth and
more coarsely branched, and while the leaves are larger the whole
canopy is much thinner. Of this variety, probably Manzanillo, a
quarter of the trees are dead and others have suffered severe sun scald.
In other cases a portion of the top has died back, to be followed by a
vigorous sprouting from below. Of a block of four rows adjacent to
this, not 10 per cent of the trees are alive, but these appear to be of a
variety little adapted to these conditions.

The cottonwoods already referred to, bounding the 20-acre block
on the west and north sides, are all dead, but so also are the olive
trees next to them. Of the Manzanillo olives, the two rows on the
north and next to the cottonwoods are two-thirds dead, while the
third row is in bad condition. 01" the trees on the west ends of the
rows next to the cottonwoods in the larger block not so large a propor-
192

26 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

tion is dead, but those alive are small and in bad condition. Figure
6 shows very distinctly the effect of the cottonwood growth on the
olives. The struggle has been so intense for a bare survival on the
part of the whole plantation that the competition with a powerful
feeder like the cottonwood has proved fatal, though the cottonwoods
probably, survived the olives but a few years.

Crossing the conduit to the next 20-acre block, only half of which
was set, are two small blocks of olives, 6 acres in all, with 4 acres of
figs between them. Here the contrast between the green of the olives
on either side and the figs, which are dead save a few struggling
sprouts, illustrates in a most marked way the comparative drought
resistance of the two. Indeed, of exotic trees on this ranch only the

Fig. 6.— Olive trees which have died through competition with a row of cottonwood trees on the Pope
olive plantation, near Palm Springs, Cal. (From a photograph.)

pepper trees bordering one field show an ability to endure these
extreme conditions equal to that of the olive.'*

While trees of this slow growth and evergreen nature are conse-
quently slow in forming what the foresters call dominant and sup-
pressed classes, a close inspection of this grove shows such a work to
be in progress, not as is generally the case in a forest by the process
of dominant trees overtopping and shading the weaker ones, but by
means of dominating root systems by which once a tree has gained

n A visit was made to this plantation on April 13, 1908, at which time about 20 per
cent of the trees of the more resistant variety of olives was in blossom, but at a later
visit, June 11, not a single fruit could be found to have set. On the same date two
olive trees in Dr. Wcllwood Murray's irrigated garden in Palm Springs village were
carrj'ing fair crops of fruit.
192

OLIVE BOOT SYSTEMS. 27

the ascendancy in water appropriation it will sooner or later have
three or four adjacent trees in the suppressed class. This suppression
of the weak trees by the stronger rooted dominant ones begins as soon
as the roots meet in the intermediate territory, which has happened
in many instances in this grove and seems to account for the death of
many of these trees and the weak condition of others. This affords
conclusive proof that olive trees can not be grown successfully 2 1 feet
apart under light rainfall without ample irrigation, and, what is more
significant, that when given wide planting they are capable of extend-
ing their root systems and collecting their water supply from a very
wide area.

OLIVE ROOT SYSTEMS ADAPTED TO UTILIZE LIMITED RAINFALL.

The remarkable endurance of drought displayed by the olive trees
of which an account is given in this paper, but especially by those at
Palm Springs, Cal., must be explained (1) by unusual ability to collect
moisture from a soil supply normally deficient and (2) by an ability
to conserve that moisture and perform their physiological work on a
supply that would prove totally insufficient for ordinary trees. For
the first we must look to the roots, and as these were uncovered and
plotted it became evident that the deeply penetrating system pos-
sessed by the mesquite for bringing up water from a subterranean
source was not possessed by the olive, nor would it have availed much,
as on near-by land a well had been sunk to a depth of 80 feet, disclos-
ing only dry cobblestone and gravel. No penetrating taproots were
found, but usually each tree had a deeply-seated burl or swelling two
or three times the diameter of the trunk above ground, from which
radiated evenly in all directions a strong set of roots running off nearly
horizontally. Plate IV, figure 1, shows the trunk, burl, and main
roots of a tree which was selected for study from the most resistant
variety of the Pope plantation.

This tree was barely 6 feet in height, with a top spread of 7 feet and
a trunk diameter of 3f inches ; yet we find a root system radiating to
10 and 1 1 feet in nearly all directions and having a total length of
roots of one-eighth of an inch in diameter and upward of about 185
feet. The length of roots was at least double that of the twigs and
branches of similar diameter, while the area occupied by the roots was
nine thnes that of the spread of the branches.

The strongly gnarled burl was a foot in depth, and from this the roots
issue at depths of 2 to 10 inches. With but a few exceptions they
all break up into fine rootlets at depths of 5 to 8 inches, the greatest
number being at 6 inches. In two cases small laterals penetrate to
18 inches in depth, and there was a curious case of branches from
two separate roots going down at the same ])oint — possibly an old
burrow of some rodent affording a more mellow soil — to 3G and 42

192

28 DROUGHT EESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

inches, respectively, beyond which point they were not excavated
and were still one-eighth of an inch in diameter.

The block of the Manzanillo variety at the north end of the 20
acres showed a different behavior from that of the main body of the
grove. The wood growth averaged much ranker, but the branches
were coarser and the tops more open to the sun. Far less adapta-
bility to conditions is evident. Dead trees, trees with dead tops but
with live sprouts from below, dead branches, and sun-scalded spots
on exposed places are to be seen on every side. In this block the tree
selected for study was 8 feet high, with 8 feet spread of top and a
trunk 5 inches in diameter. A still stronger root system was found
here, there being ten roots of from three-fourths of an inch to 1^
inches in diameter springing from the burl at the following depths
below the surface: Two at 2 inches, one at 3 inches, one at 12 inches,
three at 14 inches, two at 16 inches, and one at 18 inches. It being
evidently impossible to keep track of all of these at one excavation
the surface roots were excavated by themselves. These comprised
three strong roots, issuing at 2 and 3 inches below the surface, and a
circle of short fine roots, which the writer called the shade roots from
the fact that they occupy the space immediately beneath the spread
to the top.

Figure 7 shows these superficial roots represented in solid lines,
while the deeper roots are shown by dotted lines, but it should be
noticed that a number of the shallow roots figured came up to join
this class from roots of deep origin. These shallow roots taken
together may be regarded as a very important part of the equipment
of the tree. Their rootlets reach to quite near the surface, so that
they are prepared to gather moisture from a small rainfall. The shade
roots appear to collect also the water which is arrested by the top
and runs oft' to the ground from the trunk. It must be remembered
that the medium in which these trees grow is so nearly pure sand as
scarcely to be called a soil. There is a good deal of fine material in it,
but it does not bake or pack, and cracks never occur. It is very doubt-
ful whether any method of soil culture, dust mulch, or subsurface
packing would be of value here. All that such treatment is expected
to accomplish is already insured by the nature of this soil, and,
furthermore, any cultivation would only destroy these delicate root-
lets so nicely adapted to taking advantage of the lightest rainfall.
Referring to the deeper roots in figure 8, we notice first the large area
occupied by them as compared with the spread of the top. The roots
of this tree over one-eighth of an inch in diameter have a total length,
including the upper layer, of approximately 376 feet. The area of
the root spread, as compared with the spread of the top, would be a
little more than 7 to 1.

192

OLIVE ROOT SYSTEMS.

29

9

The depth of the course followed by these large roots of 12 to 18
inches is a very marked feature. Most interesting is the deep pene-

24\ ; 12'

S.

Fig. 7.— Diagram showing the distribution of superficial roots (solid lines) and deep roots (dotted lines)
of a Manzanillo olive tree on the Pope olive plantation, near Palm Springs, Cal.

tration, almost vertically, of branches from many of these roots to
depths of 2, 3, 4, and even 5 feet, where they were left, owing to the

mm

Fig. 8.— Diagram showing the root system of a typical dry-land olive tree on the Pope olive plaiitat
near Palm Springs, Cal., showing the jjosition and distribution of the roots in the soil.

difficult nature of the digging. In most cases gi-avel and cobb
stones of considerable size were encountered at these depths, and

192

ion,

le-
as

30 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

these were all okl, hard roots it seems probable that they had gone
down to these depths during the years when the orchard was still
irrigated. The rootlets branching from these and all the deeper
lying roots were much fewer than those nearer the surface.

A point previously referred to of special interest in this study is
that of a number of deep-lying roots at points several feet from the
tree sending off branches which rise suddenly to the level of 4 to 8
inches, along which levels they make a growth of several feet, sending
off numerous branchlets and small feeding rootlets. These ascending
laterals were found to show but three or four rings of annual growth
while the main root (though it was impossible to count the rings accu-
rately) was several years older. Evidently the upper growth had been
made since irrigation ceased in an efiort to reach the more favorable
conditions for moisture and air at the upper level. In both trees
studied, as well as in many others where small excavations were made,
fine-feeding rootlets were found in considerable numbers at 2 to 24
inches in depth, Init the zone of their greatest abundance was at
4 to 10 inches. Plate IV, figure 2, shows a section of a long root
from a depth of 6 inches, with lateral branches and feeding rootlets,
from a photograph of exactly natural size.

MOISTURE ECONOMY AIDED BY THE STRUCTURE OF THE OLIVE

LEAF AND STEM.

In addition to the elaborate arrangement of olive roots for collecting
the last particle of moisture possible from a sandy desert soil, there
must still exist a remarkable economy in tissues and functions to
enable a tree to survive, not to say to make growth, under such con-
ditions.

It is to the leaves that we must look chiefly for this work. Their
narrow form, reflexcd margins, thickness, and tough leathery texture,
as well as the densely hairy, almost felted under surface, all indicate
that they are prepared to resist to the extreme the drying influence
of the desert air. The minute anatomy of the leaf and stem of the
olive has received considerable attention from botanists, but ap-
parently no attempt has hitherto been made to ascertain to what
extent difl'erent environments aft'ect modifications of structure. That
some light might be had on this most interesting point, material was
procured by the writer of this bulletin from olive groves of California
and Arizona, the samples being obtained from such widely diverse
environments as the moist, fog-laden air and ample irrigation of
Niles, near the San Francisco Bay, and the extreme of desert dryness
and heat of Palm Springs, Cal. These were placed in the hands of
Dr. Theodore Holm, whose study of them, illustrated in Plate V,
figures 1 and 2, and five text cuts, is given in the Appendix to this
bulletin.

192

DKY-LAND OLIVE CULTURE IN C'ALIFOKNIA.

31

SUCCESSFUL DRY-LAND OLIVE CULTURE IN CALIFORNIA.

In contrast with the mere endurance test of wliich the preceding
examples are very instructive ilhistrations, there is in the so-called
''inside" region of southern California, between the ocean and the
mountains, an ohve industry based on the local rainfall on lands above
canal lines or lacking a sufficient water supply. Excellent examples
of this type of ohve culture may be found in the neighborhood of
Beaumont, Riverside County; La Mirada, Orange County; Chats-
worth and San Fernando, Los Angeles County; in Santa Barbara
County; and also in the more northerly part of th(^ State near Oroville.

■^5
JO

'O

o

■

-

•■

\

1

1

1

1

-

1

1

1

-

1

1

1

1

Fig. 9. — Diagram showing the annual rainfall at Los Angeles, Cal., as presented in Table VI.

While varying considerably in their climatic conditions they all
agree in these general features: A minimum temperature never below
20° and seldom lower than 28° or 30° F. ; a maximum summer temper-
ature of 105° in cooler seasons to 114° F. in extremely hot years,
but with a monthly mean temperature not below 48° in winter and
seldom exceeding 80° ¥. in summer. From a study of Table VI,
represented graphically in figure 9, we may see that the annual
rainfall at Los Angeles has exceeded 12 inches during more than half
of the years recorded, occasionally rising to 22 or 23 inches, or even
higher, and only in rare years of drought falling as low as 7^ inches,
with the minimum of 4.83 inches during the thirty years recorded.

57054=— BuL 192—11 3

32 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.
Taijlk VI. — Annual rain/all at Los Angeles, Cal., 187S to 1907, inclusive.^

Year.

Inches.

Year.

Inches.

1878

20.86
17.41
18.65
5.53
10.74
14.14
40.29
10.53
16.72
16.02
20.82
33.26
12.69
12. 84
18.72

1893

21 96

1879

1894

7.51

1880 .

1895

12 55

1881

1896

11 80

1882

1897

14 28

1883.

1898

4 83

1884

1899. . ..

8 69

1885 .

1900

11 30

1886

1901

11 96

1887

1902

13.12

INSS

1903

14 77

1SX9

1904

11.88

1893

1905.

19 19

1891

1906

21 31

1892

1907

15.30

a For the data usel on the c-limale of California, the writer is indebted to Mr. A. 15. Wallaber, jf the
Climate and Crop Service of the United Stites Weather Riireau at Lo.s .Vnjieles. Cal.

Table V'II. — Mean relative humidity at Los Angeles, Cal."

Month.

January.
February
March . . .
April...

May

Julie

July

5 a.

m.

5 p. m.

67

64

73

C3

80

65

82

13

87

(5

87

61

90

C2

Month.

August

September
October. . .
November.
December.

Year

5 a. m.

o p. m.

82
78
64
61

78

63
63
68
65
64

64

a For the data used on the climate of California, the writer is indebted to Mr. A. B. Wallaber, of the
Climate and Crop Service of the United States Weather Bureau at Los .Vngeles, Cal.

The rainfall of this region is enhanced by frequent coast fogs. The
mean relative humidity from month to month is an important factor
in all such cultural problems, but this is obtainable only for Los
Angeles, with which point we may fairly compare Los Angeles County
and Orange County. This, it will be seen from Table VII, ranges
from 61 to 90 per cent for the 5 a. m. observation, and from 61 to 68
per cent for the 5 j). m. observation. This condition of atmospheric
moisture would give orchards in these locahties a great advantage,
for instance, over the one studied at Palm Springs in the edge of the
Colorado Desert, except that the trees suffer more from the attacks
of parasites in the more humid climate.

One of the most extensive examples of olive culture without irriga-
tion in this region is to be found on a large ranch in the southern part
of Los Angeles County, near La Mirada, Cal. Here are 500 acres in
olives, the oldest set sixteen years ago and others as recently as seven
or eight years ago. The planting distance was only 20 feet, giving
108 trees to the acre. The olives occupy rolling hillside land for the
most part, difficult of irrigation even if a water supply were at hand.
The soil is as a rule a rather strong adobe, with some admixture of
sand in i)arts of it. The nature of the hills nearest would indicate an
abundance of lime in this soil, wdiich is so important for olive produc-
tion. Some degree of cultivation is given between the rows, but with

10-2

DKY-LAND OLIVE CULTURE IN CALIFOENIA. 33

the older trees the spread of the branches prevents reacliing all of the
surface.

The original plan was to remove half of the trees as they began to
crowd by cutting out every other row on the diagonal. The effect of
this is to leave one-half, or 54 trees to the acre, in rows 20 feet apart,
and trees 40 feet apart in the row alternating. This has been done
with some blocks of the older trees and is a very evident gam. Wliere
the original stand of the older trees still remains there is evidence of
crowding and lack of thrift in many cases, and the writer is convinced
that a stand of only 27 trees to the acre, or 40 by 40 feet, would be
still better as the trees advance in age. The great vigor and pro-
ductiveness of the trees along the draws and low places where any
surplus of rain would flow give evidence that water famine had been
felt by the small trees.

A notable feature of this orchard was the prevalence of the common
black scale, a parasite found on olive trees all along the range of the
ocean fogs unless vigorously combated, and not found to a harmful
extent in the interior valleys of California or Arizona. How seriously
this scale interferes with the functions of the tree is a matter upon
which olive growers differ widely, but there is no difference of opinion
as to the scale preventing the production of an olive of good pickling
qualities.

Of the varieties planted, the Mission is the most prominent and
satisfactory, though considerable blocks of the Nevadillo, the Pendu-
lina, and the Columbella are also grown.

Plate VI, figure 1, shows a general view across a small valley in
this orchard, and figure 2 a view among the rows of older trees thinned
by removing alternate diagonal rows.

In comparison with this orchard stands the case of a ranch 2 or 3
miles away, the soil and location being practically the same. Here
400 or more acres of olives, probably differing little at the start, have
for several years been in absolute neglect. Many of the trees v>-ere
never properly headed up, being mere stools of several shoots from
the ground. No evidence of cultivation could be seen, but grass,
weeds, and small shrubs robbed the trees of the needed moisture.
This, with the close planting, had reduced the problem to one of
existence instead of profitable production. There was some fruit,
and occasional trees enjoying some little advantage in space and
moisture were bearing fair crops. These only helped to j)rove the
fallacy of the idea that the olive is a tree that may be planted ujion
dry and barren soil, given absolute neglect, and yet produce profitable
crops of fruit. Here in these contrasted orchards, with soil, rainfall,
and temperature similar, the difference between pruning and culture
on one hand and neglect on the other made the difference between
a profitable industry with a fine product and a poor and scant crop
not worth going over the ground to gather.

192

34 DROUGHT KESISTANCE OF OLIVE IN SOUTHWESTEKN STATES.

AREA OF POSSIBLE DRY-LAND OLIVE CULTURE IN THE UNITED

STATES.

AREA LIMITED BY THE MINIMUM TEMPERATURE.

Of the factors defining the area of ohve culture in the United wStates,
that of minimum temperature is the most important.

It has been claimed by some authors ® and by many olive growers
that an actual minimum temperature of 14° or 15° F. will prove fatal
to the olive tree. It is undoubtedly true, however, that the olive
will endure considerably more cold than this if it is in a thoroughly
dormant condition. This is especially true where the atmosphere
is dry and where the low temperature persists for only a short time,
possibly a few minutes at near daylight, as is so often the case in the
southwestern sections.

As an illustration of these ideas, in 1899,'' from February 11 to 13,
a cold wave of unusual intensity swept over a great portion of the
Southwest, temperatures of -6° to —23° F. being recorded in north-
ern Texas, and as low as 8° F. in the southwest border.

At San Antonio two stations gave minimum records of 4° F. At
Fort Mcintosh, on the Rio Grande near Laredo, a minimum tem-
perature of 5° F., probably for only a brief period, was recorded
on the morning of February 12, and at Fort Ringgold, 90 miles dowQ
the river, a temperature of 7° F. was recorded on the morning of
February 13.

An olive grove of an acre or more about 2 miles from Fort Mcin-
tosh suffered some killing back, though the trees were not seriously
injured and may be seen to-day looking as vigorous as any in the
olive-^rowdno; districts of California or Arizona.

At the dry-land experiment station of the Bureau of Plant Industry,
near San Antonio, Tex., young olive trees of the Chemlali variety
endured a minimum temperature during the winter of 1907-8 of 18°
F., with but a slight killing back at the tips. Yet in 1909 these olive

a A temperature of 5° C. below zero (or 23° F.), followed by a sudden thaw operated
by the sun's rays, is sufficient to kill it totally at the base. With a lower temperature
not followed by sunny days the plant does not suffer as much, as it can stand a cold
of 10° C. below zero (or 14° F.). — Olive Culture, Italy, Annual Report of the State Board
of Horticulture, California, 1890, p. 449.

"A low temperature, say 14° F., is fatal to the tree."— 5. M. Lelong, Investigation
Made by the State Board of Horticulture of California Olive Industry, Sacramento, 1900,
p. 8.

"The olive can grow in all regions where the minimum temperature does not fall
below —7° or —8° C. and does not last more than eight days." — Translation from
Hidalgo Tahlada.

b Annual Summary, 1899, Texas Section, Climate, and Crop Service, Weather
Bureau, U. S. Dept. of Agriculture,
192

AREA OF POSSIBLE DRY-LAND OLIVE CULTURE. 35

trees and trees of several varieties i)laiite(l in 1908 were with one
exception killed to the ground under conditions where the minimum
temperature reached was only 18° F. After mild weather during
the latter part of December and the early part of January, with
maximum temperatures of 76° and 77° on January 9 and 10 and 63°
F. on the following day, a "norther" brought the temperature to
20*^ at 3 p. m. on January 11, with a minimum of 18° F. at night.
On January 12 the minimum was 18° with a maximum of only 22°,
and there was a minimum of 22° on the morning of January 13, the
temperature thus being maintained about forty hours at from 10° to
14° below freezing. These trees were in a plat which in accordance
with the general cultural policy of the farm had been kept under
fine surface tillage, enabling the soil to store abundant moisture from
the season's rains. This arrangement prevented the olive trees from
entering the dormant condition necessary to their resisting the low
temperatures, and the freezing sap burst the bark of most of them
and killed all to the crown, from which they sprouted again freely.

At Boerne, 30 miles northwest of San Antonio and 700 feet higher
in altitude, the temperatures registered were 1° lower each day of this
cold spell than those at the San Antonio farm, yet the olive trees
there sustained much less injury.

A region may have monthly mean temperatures and an annual
mean sufficient to place it high in the scale when compared with well-
known olive regions, yet where high winter means include sudden
drops and low minima the trees will suffer all the more severely. As
an example, the monthly mean temperatures at San Antonio are
higher throughout the year than those of Fresno, Cal., or of Catania,
in Italy, and excepting only the autumn months, liigher than those
of Sfax, in Tunis, three representative olive-producing regions.
Yet the liabihty to the sudden advance of cold waves may upon
experimentation be found to exclude this portion of Texas entirely
from the olive-growing belt.

It seems probable also that there is a considerable difference in
olive varieties in resistance to cold, and an inviting. field for experi-
mentation is here offered.

The high altitudes of the greater portion of New Mexico will
doubtless exclude the olive on account of too severe cold. However,
it seems probable that favored mesa sites may be found in the south-
western portion of the Territory, particularly in Grant and Dona
Ana counties, where the olive may be grown.

French authorities "^ give the maximum range in altitude for the
olive as from 500 meters (1,600 feet) in France and northern Italy to

a Investigation Made by the State Board of Horticulture of the California Olive
Industry, Report to Governor Gage, 1900, p. 8.

192

36 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

700 meters (2,300 feet) in Sicily, it being even affirmed that it ascends
as high as 800 meters (2,600 feet) on that island.

Simmonds, in his "Tropical Agriculture," states that the olive
grows at Quito, under the equator, at a height of 8,000 feet above sea

level."

According to the reports of the Cahfornia State Board of Horti-
culture'' the olive does well at an altitude of 3,000 feet at 37 degrees
latitude in the Sierra Nevadas. In the southern part of Arizona it
is probable that it may thrive at still higher altitudes, possibly at
5,000 feet. Nor could a safety hne of altitude alone be defined, for
some higher spots favorably situated will be found to be more reliable
than lower locations adjacent.

In California the ohve grows well around San Diego, and from
there along the coast northward to the upper end of the State and
up into small valleys of the Coast Range. Farther inland the suc-
cess would be limited by altitude, but it can be depended upon
throughout upland portions of the greater area of the interior val-
leys and to altitudes of about 3,000 feet in the foothills. In Arizona
areas of olive territory may be looked for as far north as the Gila
River in Pinal County and farther west to the north hne of Maricopa
County, with probably the western limit at about the meridian of
Gila Bend, on account of reduced rainfall. (See Table VIII.)

Table YIIl .—Localities in Arizona where dry-land olive culture may be possible, ivith

meteorological record, c

station

Length
of record.

Altitude.

Mean an-
nual tem-
perature.

Mini-
mum for
1908.

Date of killing frost,
1908.

Precipi-
tation,

Spring.

Fall.

1908.

Congress

Years.

12

10

7

12

9

6

19

14

18

28

25

16

10

Feet.
3,668
1,900
3,362
4,743
2,300
3,525
2,456
1,108
2,360
2,390
3,523
4,500
4,550

" F.

67.2
68.2
61.2
60.8
63.9
62.9

° F.
29
29
22
22
23
24
23
30
24
22
21
10
25

Feb. 4
Feb. 16
June 4
Apr. 17
Apr. 9
Mar. 28
Apr. 4
Mar. 8
Mar. 23
...do....
..do

Nov. 9
Nov. 25
Oct. 18
Sept. 29
Oct. 24
Oct. 19
Oct. 21
Dec. 21
Oct. 22
Oct. 19
...do....

Inches.
13.15

Columbia

15.40

Kingman

11.77

Jerome

18.32

Cline

15.94

Globe

16.51

San Carlos

12. 78

Phoenix

Dudley ville

Tucson

69.5
65.0
67.5
66.1
62.0
62.1

d7.88

14.00

10.69

9.03

Oracle «

Tombstone

Mar. 29
Feb. 28

Dec. 4
Nov. 18

25.90
14.00

a " In the neighborhood of Quito, situated under the equator, at a height of 8,000 feet above the level
of the sea, where the temperature varies even less than in the island climates of the temperate zone, the
olive attains the magnitude of the oak, yet never produces fruit."— P. L. Simmonds, Tropical Agricul-

tUT€ 7). 39-i •

b Investigation Made by the State Board of Horticulture of the California Olive Industry, Report to
Governor Gage, 1900, p. 8.
c Annual Summary, 1908, Arizona Section of the Climatological Service of the Weather Bureau.
d Mean annual, Weather liureau, U. S. Dept. of Agriculture.
e Climatology of the United States, Bulletin ",Q," Weather Bureau, U. S. Dept. of Agriculture.

192

AREA OF POSSIBLE DRY-LAND OLIVE CULTURE. 37

AREA LIMITED BY HEAT REQUIREMENTS.

While the Pope ohve grove has been studied as a case of survival
without fruiting in spite of extreme adverse conditions, yet in the
garden of Dr. Wellwood Murray at Palm Springs Hotel, with an
ample shelter belt of trees around the border, two trees. of the Pendu-
lina variety have made a good growth and ripen fair crops of fruit
with only scant irrigation, though there is scarcely a summer when
a temperature of 120° to 122° F. is not recorded.

As to the maximum temperature which the olive will withstand, it
is hard to find a locality in the United States where a fair degree of
success may not be met with.

Contrary to the often-expressed opinion that it is only successfully
grown in regions adjacent to the seacoast " the olive thrives and
produces abundantly in such hot interior locahties as Biskra, Algeria;
Fresno, Cal.; and Phoenix, Ariz.

At Phoenix, Ariz., maximum summer temperatures of 112° to 116°
F. are matters of record, with a July mean of 90° F. The mean
temperatures for the months of June, July, August, and September
are 6 to 9 degrees higher than those of Catania, the warmest olive-
growing station of Italy,* and compare quite closely throughout the
year with the mean of Biskra, Algeria. (See fig. 10.)

There is near Phoenix a small but flourishing olive industry under
irrigation, the trees making a rapid, healthy growth and bearing good
crops of olives, yielding oil of an excellent quality. This affords
proof of the high temperature which the olive will sustain when that
factor alone is taken into account.

There is an area through the more wind-exposed portions of the
Colorado Desert where it is possible that the hot, dry winds of the
early spring prevent, as a rule, the setting of the fruit, though the few
trees to be found there make a fair growth with a minimum of
irrigation.

For the development of the olive fruit a rather constant number of
heat units above the dormant or zero point of the olive tree is needed
during the active or growing season. For convenience in transcrib-
ing the data from weather records, however, these heat units are here
assumed in degrees above zero, Fahrenheit. Thus, as the mean tem-
perature of Phoenix, Ariz., has been determined after a number of
years of recorded observations to be 52° F. for the month of January,
multiplying 52 by 31, the number of days, gives 1,612, representing
the number of heat units for that month. Computing each month
in the same manner, their sum amounts to 25,607, the number of
heat units for the year.

tt Caruso, G. Dell' Olivo, Turin, 1883, p. 34.
192

DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

Tabic IX shows the mean nioiilhly and mean annual temperatures,
with the sums of heat units for twelve localities of the olive-growing
regions of Europe, Africa, and the United States, selected to show a
range of temperatures from that at Bologna, Italy, with an annual
mean of 57.16° F. and 20,895 heat units, which is slightly too cool, to
that of Palm Springs, Cal., where there is probably about the extreme
of heat which the olive will endure, it having an annual mean of
72.1° F. and a summation of 26,349 heat units.

Table IX. — Mean temperatures and summation oj temperatures, by months, at points
in Algeria, Tunis, Sicibj, Italy, Arizona, and California.

Month.

January

February

March..!

April

May

June

July

August

September. .

October

November. .
December. . .

Year..

Palm
Springs, Cal.

03

°F.
56.20
57. i:0
63.96
68.02
74.19
85.06
91.55
88. 23
83.73
76. 48
63.93
55.88

72.10

c
2

03
g

3
m

°F.
1,742
1,010
1,983
2,059
2,300
2,552
2,838
2,735
2,512
2,371
1,918
1,729

26, 349

Biskra.
Algeria."

a

C3

"F.
50.5
53.0
60.5
68.0
75.0
82.0
93.2
90.0
87.5
75.0
61.0
53.0

70.7

02

°F.
1,565.5
1,584.0
1,875.5
2,040.0
2,325.0
2, 460.
2,889.0
2,790.0
2,625.0
2,325.0
1,830.0
1,643.0

25,952.0

Phoenix,
Ariz.

°F.

52

56

60

67

75

85

90

89

83

71

61

52

"F.
1,612
1,568
1,860
2,010
2, 325
2,550
2,790
2,759
2, 490
2,201
1,830
1,612

25,607

Tucson,
.'Vriz.

°F.

50

54

59

66

74

82

88

86

81

70

59

52

08

a
o

B
E

°F.
1,550
1,512
1,829
1.980
2,294
2,460
2,728
2, 666
2,430
2,170
1,-770
1,612

25,001

Sfax,
Tunis. h

C3

°F.
51.3
54.4
59.1
03.2
68.8
72.8
78.5
79.3
78.4
72.8
61.8
54.0

66.2

c
_o

E
S

3

°F.
1,590.3
1,523.2
1,832.1
1,896.0
2,132.8
2,184.0
2,433.5
2,458.3
2,352.0
2, 256.
1,854.0
1,674.0

24, 186. 2

Catania,
Sicily. c

c
o

c3

°F.

50

52

56

60

68

76

81

82

77

68

60

54

66

°F.

1,550

1,456

1,736

1,800

2,108

2,280

2,511

2.542

2,310

2,108

1,800

1.074

23.875

Month.

January

Fresno,
Cal.

Los Angeles,
Cal.d

"F.
45

I'"ebruarv : 51

March.

April

May

June

July

August

September.

October

November.
December..

Year .

c
2

E
E

c

cS

"f

'F.
1,359
1,428
1,674
1,800
2,077
2,250
2,542
2,511
2,220
1,984
1,650
1,426

63 22,921

°F.

54.2

55 .'5

56

59

62

66

68

71

69

64

60

56.5

62.3

3
M

"F.
1,070.
1,554.
1,703.
1,782.
1,937.
2,001.
2,135.
2,213.
2,085.
2,005.
1,812.
1,751.

22, 712. 1

San Diego,
Cal.

°F.

54

55

56

00

02

65

OS

70

66

64

59

56

61

c

a
E
E

3

"F.
1,074
1,540
1, '36
1,800
1,922
1,950
2, i08
2,170
1,980
1,984
1,770
1,736

22,370

Pisa, Italy. f^

a

C3

°F.

44
49
52
00
05
71

62
52
50

60.75

a
o
'^

C3

E
g

3

o jp

1,364

1,.372
1,012
1,800
2,015
2, 1,30
2, 387
2,325
2,100
1,^82
1,.500
1,550

22,257

San Jose,
Cal.

Bologna,
Italv.c

°F.

48"

51

54

50

60

66

07

67

65

60

54

50

a

03

E
E

3
W

o jp

1,488
1.508
1,674
1,680
1,860
1,980
2,077
2,077
1,950
1,860
1,020
1,550

58 21,384

°F.

36
42
48
58
65
72
78
74
69
58
46
40

57.16

■d

03

E
S

3
02

o jp

1,110
1,176
1,488
1,740
2.015
2,160
2,418
2,294
2,070
1,798
1,380
1,240

20,895

a From Bulletin 53, Bureau of Plant Industry, U. S. Dept. of Agriculture, p. 64.

bFrom Bulletin 125, Bureau of Plant Industry, U. S. Dept. of Agriculture, p. 14.

cFrom "The Olive, Its Culture in Theory and Practice," by A. T. Marvin, San Francisco, 1888.

d Computed from data furnished by Mr. A, B. Wallaber, United States Weather Bureau, Los .\ngeles,
Cal.

eMean temperatures from "Climatology of the United States," Bulletin "Q", Weather Bureau, U. S.
Dept. of .Vgriculture.

192

Akea of possible dey-land olive culture. 30

Caruso" states that the olive sap begins to stir at a temperature
of 10.50° to 11° C. (which is equivalent to 51° to 52° F.) and flowers
at 18° to 19° C. (equivalent to 64.4° to 66.2° F.). Accor(hng to this
author, we must regard the zero point of the olive as about 51° to 52°
F., but the temperature figures in Table IX indicate that for such
localities as Palm Springs and Los Angeles in California and Phoenix
and Tucson in Arizona the zero point must be somewhat higher,
probably 55° to 56° F.

To ripen the fruit within a period of safety from autumn frosts,
there must be a sum of about 16,400 heat units within six or seven
months from the starting of vegetation. Allowing seven months
this would be equivalent to about 16,400 units from, say, the middle
of March. In order to correlate this seasonal estimate with the
summation of average annual heat units, as shown in Table IX,
we will add to the above sum the number of heat units from January
1 to March 15 for Pisa, Italy, a typical olive locality, and we have a
summation of 20,070 units, which would throw the olive ripening at
Pisa to about November 20.

Hidalgo Tablada '' gives the temperature for the flowering of the
olive at 19° C. (66.2° F.) and states that at Seville this is reached about
]\Iay 1. From that statement, the accumulation of 3,978 units C.
(12,376 F., allowing one hundred and sixty-three days) is sufficient to
mature the fruit, which will be accomplished early in October, after a
growing season of 27.3° C. (81.14° F.) mean temperature. These
dates of seasonal activity of the olive can be regarded only as
approximations, there being variations due to localities as well as to
varieties of fruit.

Data regarding the olive in relation to climate in the United
States are rather meager, but wduit we have coincide in a very inter-
esting way with the European observations.

Figure 10 is a graphical showing of the data of Table IX, summing
up the heat units in columns for each locality, the monthl}^ sumrna-
tions being carried between the heavy black lines across the chart.
The heavy dotted horizontal lines show approximately the seasonal
activity of the olive as it relates to these summations.

The phenological records for the olive at Phoenix, Ariz.,'^ for the
year 1907-8 show the average date of full bloom of the olive to be

a Caruso, G. Dell' Olivo, Turin, 1883, p. 34.

& Hidalgo Tablada, Jose de. Tratado del Cultivo del Olivo en Espana y Modo de
Mejorarlo, Madrid, 1899, p. 74.

cSee the phenological records for Phoenix, Ariz., for December, 1907 and 1908,
in the Arizona section of the Climatological Service of the Weather Bureau, U.S. Dept.
of Agriculture.
192

to

40 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

about May 1, at mean temperatures of 66° to 71° F., shown by line
(7, figure ]0.

The ohve harvest is noted as beginning from October 8 to 10 and
as completed during the latter part of December. The growing
period from flower to earliest ripe fruit averages one hundred and
sixty-three days at a mean temperature of 81.6° F., giving a sum-
mation of 13,314 units, which corresponds very closely with the fig-
ures of Caruso and Tablada. Adding the means, 7,050 units from
January 1 to May 1, we have a total of 20,364 units.

For the full maturing of the crop of medium varieties, 24,000 to
25,000 units will be needed at this station, while late-maturing sorts
will not ripen till well into the winter. Ileferring to the diagram
(fig. 10) the line I) indicates 20,364 units, which occur early in October

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Fig. 10.— Diagram showing the monthly means and summation of heat units of places in the olive-growing
regions, illustrating the seasonal activity and heat requirements of the olive, arranged from Table IX.

for Phoenix, late in November for Los Angeles and Fresno, and barely
within the year at Bologna, Italy. Caruso states that the latter place
is too cool for the olive, on account of the frosts of December and Jan-
uary, but that the fruit matures in sunny localities on the hillsides not
far from the town. In localities having low summer means but with
little or no frost in the winter months, such as San Jose and Santa
Barbara, Cal., where the re([uisite number of heat units for the first
ripening of the fruits will barely be accumulated b}^ the end of
December, the olives may remain on the trees throughout the suc-
ceeding winter months. Where the summation of about 21,000 de-
grees can not be reached before such low autumn temperatures prevail
as will injure the fruit, olive growing should not be undertaken.

192

AREA OF POSSIBLE DRY-LAND OLIVE CULTURE. 41

AREA LIMITED BY RAINFALL.

Taking up the consideration of rainfall, the industry must be con-
sidered from a different standpoint from that in which olive growing
has been viewed in this country in the past. The usual planting dis-
tance has been from 20 to 24 feet. With abundant water the trees
might prosper and produce remunerative crops with this area to draw
from. Wlien dependent upon local rainfall they have shown signs
of failure.

In the valuable pamphlet on olive culture entitled "Investigation
Made by the State Board of Horticulture of the California Olive
Industry, Report to Governor Gage," 1900, page 29, is found a very
significant discussion of the water problem by the Hon. Frank A.
Kimball, the substance of which is as follows: Olive trees set at the
ordinary orchard distance in this region, usually about 116 trees to
the acre, gave during their earlier years very excellent results with-
out irrigation. The growth was vigorous and the fruit large and
fine.

Mr. Kimball gives a graphic account of their condition a few years
later, as follows:

The trees on becoming large required the necessary moisture to develop their growth,
which had now assumed immense proportions. The soil could not furnish the require-
ments of the trees, and in the summer they lost the larger portion of their leaves. They
remained in this semidormant condition until the rainy season set in or moisture
from the soil began to rise. Most of the fruit dropped, and what did not fall did not
attain a size suitable for picking. This condition of affairs continued until the growers
resolved to apply water. After a season or more of demonstration they found irri-
gation to be one of the essential means through which a crop of fruit can be assured.

The reason why we do not get olives is, the trees are starved, if want of water can
be called starvation. For lack of water the soil can not furnish the material from which
the olive is made.

The idea that the olive trees need a certain minimum volume of
water for the performance of their physiological work is a fundamental
one, but it does not seem to have occurred to these growers that by
reducing the number of trees to the acre, thereby giving to each tree
a sufficient area to afford the needed moisture, the same results
might be secured as by irrigation. The olive has shown its ability to
send out a root system that will secure the needed moisture from the
larger area of soil and maintain a high productiveness. This has
been shown by Mr. T. H. Kearney's study of the dry-land culture of
the olive in Tunis, now accessible in Bulletin 125 of the Bureaii of
Plant Industry. From this publication we learn that a great olive-oil
industry is carried on in Africa on lands receiving normally only
from 9.3 to 15 inches of rainfall annually, while several good cro})s
were produced during a period of seven years when the rainfall
averaged only 6 inches, according to the French records.

192

42 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

The secret of this Hes in wide planting, not nioi-c than 11 trees to
the acre, and in clean cultivation, keeping the soil in a condition
to receive every drop of rainfall and to conserve it to the utmost, the
varieties used, chiefly Chemlali, being especially adapted to such
conditions and affording a high percentage of oil.

The examples presented in this paper are those of the endurance
of extremes of drought and neglect by varieties of the olive com-
monly grown in the south of Europe under conditions of sufficient,
if not abundant, moisture. Their growth as trees in these arid
situations in Arizona and California, interesting and suggestive as
it is, would not warrant their maintenance as a commercial oil-
producing enterprise. But the Chemlali and other varieties of the
olive are profitably grown for oil production in the north of Africa
without irrigation, and under conditions of soil and climate fairly
comparable with those endured by the Arizona groves herein described.
Whether the Chemlali variety will make the profitable growth in
Arizona, California, and other sections of the Southwest that it has
in Tunis can only be determined by careful experimentation.

The possibility that large areas of land within the proper tempera-
ture limits and having an ideal soil for the olive, yet without the
rainfall or irrigation water necessary for ordinary crops, may be
utilized for an olive-oil industry makes it worth while to institute
experiments of sufficient extent to thoroughly test the matter. Plant-
ings of more than an experimental character are not warranted by
the present extent of our information, and the production of pickling
olives is not contemplated.

In each of the instances cited where olive trees have remained
alive and growing in spite of the failure of water it is necessary to
remember that the plantation was established under irrigation.
Likewise, in Tunis the truncheons by which the orchards are propa-
gated are carefully watered by a supply carried from wells until
sufficiently rooted to maintain themselves, three waterings usually
being sufficient during the first summer. In making selections of
tracts for olive culture over the drier areas indicated in Texas,
Arizona, and California it inust be a further condition, of success that
a small supply of water from some source can be assured to establish
the young trees, after which a local rainfall of 7 to 12 or 15 inches
annually may be expected to support the plantation and enable
it to produce fair yields of fruit — perhaps enough to render dry-land
olive culture profitable on a commercial scale.

SUMMARY.

In several localities in southern California and Arizona olive groves
have been planted along with apricots, figs, grapes, and some other
fruits. The irrigation projects under which these plantings were

102

SUMMARY. 43

made subsequently failed, leaving the fruit trees without any water
other than the rainfall.

The local rainfall of 3^ to 8 or 10 inches annually has proved
insufficient to maintain life in any of these plants except the olive,
which has been found in many instances green and flourishing after
six or eight 3'ears of abandonment and lack of irrigation.

Under these conditions the olive has shown the characteristics of a
desert plant, competing with the mesquite, cat's-claw, and grease-
wood in their own territory. The plantations which have been
studied are the Bogart-Degolia grove near Casa Grande, Ariz., a grove
near Florence, Ariz., and "Las Palmas" trees in the olive belt north-
east of Phoenix, localities having a mean annual rainfall of 7 to 9
inches; and in California, the Pope olive grove near Palm Springs,
in the upper end of the Colorado Desert, where, with an annual
average rainfall of only 3^ inches, 20 acres of olives have survived six
years without irrigation and are still growing.

The soils of the localities are sandy and gravelly clays derived
from the disintegration of the soft granitic rocks of the adjacent
mountains. They are low in organic matter, but fairly rich in avail-
able phosphoric acid and potash. The soil at Palm Springs is a
nearly pure granitic sand and gravel, very low in silt, clay, and
humus, but showing by analysis percentages of potash and phos-
phoric acid equal to the better agricultural soils of the Mississippi
Valley.

A study of the olive trees growing under these conditions has
shown that unlike the mesquite and some other desert trees they do
not survive by sending roots down to subterranean supplies of mois-
ture, but develop instead a very elaborate system of roots occupying
the soil at from 2 or 3 to 18 inches in depth and adapted to gathering
moisture from the lightest rainfall.

The remarkable drought resistance of the olive is made possible
(1) by the power these trees possess of extending their roots so as to
gather moisture from a large area; (2) by their habit of growth in
forming low spreading tops which protect the trunk and main branches
from the burning heat of the sun; and (3) by the character of their
leaves, which are constructed in a manner calculated to check evap-
oration and conserve the moisture obtained by the roots.

The plantations studied were made according to irrigation stand-
ards and contained originally from 75 to 114 trees to the acre. These
plantings have proved too thick for successful growth without
irrigation.

The varieties usetl in these orchards are the ones commonly grown
under conditions of sufficient rainfall in France and Italy or with an
abundance of irrigation in California.

192

44 DEOUGHT RESISTANCE OF OLIVE IN SOUTHWESTEEN STATES.

The publication in 1908 of Bulletin 125 of the Bureau of Plant
Industry, entitled "Dry-Land Olive Culture in Northern Africa,"
by Mr. Thomas H. Kearney, has brought to our attention the existence
of a great oil-olive industry many centuries old, in the north of
Africa, dependent on an average annual rainfall of 9.3 inches. The
principal varieties grown are probably of local origin, adapted to
these conditions through years of selection.

Very wide planting allows a great spread of roots for moisture
gathering, while a system of clean cultivation and dust-mulch form-
ing in vogue in that country before it was occupied by Europeans
conserves to the utmost the meager rainfall.

The most drought resistant of these varieties, the Chemlali, has
been imported by the Bureau of Plant Industry, and is being tested
at a number of localities in the Southwestern States.

In view of the remarkable drought resistance shown by European
olive varieties accustomed to abundant moisture, as shown in this
bulletin, it is believed that with the planting of this desert-bred
variety from Africa and the adaptation to our conditions of the
Tunisian methods of planting and culture, large areas of land in
the Southwestern States possessing a suitable soil and climate but
now undeveloped from lack of irrigation water are adapted to pro-
duce olive oil.

Trial plantations are now being made at various points in this
region to determine whether such dry-land olive culture will prove
profitable on a commercial scale under American conditions.

192

APPENDIX.

192

45

ANATOMICAL STRUCTURE OF THE OLIVE

(OLEA EUROPEA)."

By Dr. Theo. Holm.

Fig. 11.— Transverse section of a young
lateral root of the third order of an olive
tree from Palm Springs, Cal., showing
a hairy epidermis(Ep.) and cortex(C.).

ROOT STRUCTURE OF THE OLIVE.

Characteristic of the root structure of the genus Olea is the presence
of stereome on the inner face of the pericambium and the prevalence
of cambial cell divisions on the inner face
of the leptome. Otherwise, the arrange-
ment and development of the various tis-
sues is not different from that of many
other dicotyledons.

The structure is as follows: In the
young lateral roots of the third order (figs.
11 and 12) the epidermis (Ep.) is very
hairy and covers an exodermis (Ex.) of
thin-walled cells in a single layer; this
exodermis is not contractile. The cortex
(C.) is compact and thin walled; it con-
sists of eight layers, more or less filled
with starch; a thin-walled endodermis (End.) is plainly visible, bor-
dering on the pericambium (P.) which shows isolated strands of
St. stereome (St.) outside the leptome. The

stele is tetrarch, there being four strands of
leptome (L.) alternating with four rays of
hadrome (H.), which extend to the center
of the stele. Increase in thickness begins
even in these thin roots, since cambial
(Camb.) divisions are noticeable on the inner
face of the leptome, although the increase
does not extend beyond the formation of
these few layers.

In lateral roots of the first or second order, on the other hand, the
increase in thickness attains mucli larger dimensions, due to the

a This description of the anatomy of olive roots, leaves, and stems, with ten illus-
trations, was prepared at the writer's request by Dr. Theo. Holm, of Brookland,
D. C, from material collected from several California groves.

57054°— Bui. 192 11 4 47

Fig. 12.— Inner i)ortion of the same
transverse section of the olive root
shown in figure 11, (X210.)

48

ANATOMICAL STEUCTUEE OF THE OLIVE.

activity of the pericambium in developing phellogen (Ph.) and cork
(Co.) (fig. 13), besides a secondary cortex (C*) (fig. 14), to say
notliing of the continued cambial cell divisions on the inner face of
the leptome, as observed already in the much thinner lateral roots.

The result of these various in-
creases (fig. 14) is the develop-
ment of a broad zone of cork, the
development of a secondary cor-
tex (C*), the development of a
closed sheath of pericambial
stereome (St.), and finally from
the cambial strata the develop-
ment of secondary leptome and
hadrome (L. and H.) with rays
of parenchyma (P.).

The diagram (fig. 15) shows
the arrangement of all these tissues except the epidermis and the
exodermis, which have, of course, been thrown off before this stage is
reached. The center of the root possesses remnants of the primitive
root stele, from which rays of parenchyma extend toward the sec-

FiG. 13.— Transverse section of a lateral root of the first
or second order of an olive tree, showing the develop-
ment of phellogen (Ph.) and cork (Co.). (X 120.)

Camb^

Fig. 14.— The same transverse section shown
in figure 13 of the root of an olive tree,
showing the development of a SM-ondary
cortex (C*) and parenchyma ( F . ) rays from
the cambial (Camb.) strata, (x 120.)

Fig. 15.— Diagram of the root of an olive tree, showing
the general arrangement of tissues described in figures
11 to 14, inclusive. (X 22.\.)

ondary cortex (C*). The I'oot of the genus Olea shows the arrange-
ment of the several tissues in a remarkably regular way, and the
presence of pericambial stereome is interesting.

192

LEAF AND STEM STRUCTURE OF THE OLIVE. 49

LEAF AND STEM STRUCTURE OF THE OLIVE.

The structure of the olive leaf is that of a xerophyte; in other
words, it shows in a high degree pecuharities of structure that char-
acterize most woody plants that grow in situations where both air
and soil normally contain a relatively small amount of moisture.
On the upper surface of the leaf the cuticle and outer walls of the
epidermis cells are greatly thickened, stomata are absent, and shield-
shaped hairs are scattered over the surface. On the lower face the
outer walls of the epidermis cells are very thick (though less so than
on the upper surface), the stomata are placed at the bottom of nar-
row pits, and shield-shaped hairs form a dense continuous covering.
The interior, chlorophyll-bearing tissue (chlorenchyma) consists of
three or four very compact layers of palisade cells (i. e., narrow cells,
elongated at right angles to the epidermis) beneath the upper epi-
dermis, and between the palisades and the lower epidermis many
layers of so-called pneumatic tissue, the cells of which are very irreg-
ular in shape, not much longer than wide, and inclose numerous air
spaces. Prosenchymatic cells with very thick walls (the stereome),
either singly or in groups, are scattered through the mesophyll and
occur here and there directly beneath the epidermis, as well as in
several continuous layers adjoining the midrib. Between the mid-
rib and the sheath of stereome there is no chlorenchyma, but extend-
ing to the epidermis on both sides are several layers of collenchyma,
of which the cells contain no chlorophyll and have their walls greatly
thickened, especially at the angles.

Of the foregoing characters, those which may be pointed out as
especially xerophytic are: Thickness of the cuticle and outer cell
walls of the epidermis, absence of stomata on the upper surface and
their situation in pits on the lower face, and the dense covering of
flat, shield-shaped hairs on the lower face. These characters are
supposed to be especially useful to plants that inhabit dry climates
or that grow in soils from which their roots obtain moisture with
difficulty, by protecting the leaves from excessive loss of water
through transpiration. The development of the chlorenchyma be-
neath the upper face of the leaf into several layers of compact pali-
sade tissue is also characteristic of many xerophytes.

In leaves of the olive developed in the shade or in a moist atmos-
phere, the cell walls of the epidermis are much thinner, the stomata are
level with the surface instead of being situated in pits, and the midrib
is embedded in chlorenchyma, with a much smaller development of
collenchyma.

Leaves and young twigs of olive trees were collected in abandoned
orchards at Phoenix, Ariz., and at Palm Springs, Cal. In the former
case the tree had been without irrigation for six years and in the latter
193

50

ANATOMICAL STRUCTURE OF THE OLIVE.

Fig. 16.— Ofle of the peltate hairs
from the surface of an olive leaf.
(X 150.)

case seven years. Since in both cases the ground water was out of
reach of the roots and since the average yearly rainfall in Phoenix is
but 8.11 inches and at Palm Springs only 3.5 inches, it is evident that
these leaves were produced under extremely arid conditions. In fact,
the conditions at Palm Springs probably represent the extreme of
drought that the olive tree can endure. In both cases the varieties
were not identified. For purposes of comparison, similar material of
the Mission olive, the variety most widely grown in California, was

obtained at Niles, Cal., where the trees are
irrigated at least once during the season
and where the average yearly rainfall is
14.8 inches, with a low evaporation due to
the cool summer climate. The leaf and
stem structure of the last, which may be
regarded as typical of Olea europea in the
western United States, is as follows:

On the upjjer (ventral) face the cuticle
is smooth and thick; the lateral walls of
the epidermis cells, viewed superficially,
are straight and very much thickened; stomata are wanting and
peltate hairs (fig. 16) are scattered over the surface. On the lower
(dorsal) face the cuticle is similar; the radial walls of the epidermis
cells are almost straight, but not so much thickened as on the upper
face; the numerous stomata (fig. 17) are sunken, with narrow and
not very deep air chambers, and are surrounded by a variable
number of undifferentiated epidermis cells; peltate hairs (fig. 16) are
abundant, forming a continuous covering over the blade. The outer
walls of the epidermis cells (figs. 17 and 18) are very thick on both
faces of the leaf and show an increase in
thickening very plainly. On the dorsal
face they show many deepenings caused
by the irregular thickening of the cell
wall (fig. 17). The inner and radial cell
walls of the epidermis are rather thin as
compared with the outer walls. The
unicellular stalks of the lai-ge shield-shaped hairs are located in cir-
cular cavities, the peltate part of the hair, which consists of numerous
radially arranged cells, resting upon the outer wall of the epidermis.
The chlorenchyma is difi'erentiated into palisade and pneumatic
tissues. The former (fig. 18) consists of three compact layers of very
high cells containing chlorophyll and small needle-shaped crystals of
calcium oxalate. It extends from the margins of the blade to the
midril), where it ceases, being broken by the hypodermal collenchyma.
On the dorsal side of the blade there is a thick pneumatic tissue of
many layers. The cells which, like those of the palisade, contain

eq...

Fig. 17.— a sunken stoma and the un-
even dorsal surface of an olive leaf.

LEAF AND STEM STRUCTUKE OF THE OLIVE.

51

Fig. 18.— Ventral face of an olive leaf, showing the
thickened waUs of epidermal cells and palisade cells,
(X 150.)

numerous needle-shaped crystals of calcium oxalate, are of a very
irregular shape and the intercellular spaces are very wide (fig. 19).
The pneumatic tissue, like the palisade tissue, is broken at the midrib
by hypodermal collenchyma.

The stereome is thick walled and very unequally distributed. It
occurs hypodermally (immediately beneath the epidermis) as single
cells or a few cells together on
both faces of the blade (fig. 18),
as scattered cells in the col-
lenchyma (PL V, fig. 1), and as
a pericycle of several continuous
layers in the midrib (PI. V, fig.
1). It is characteristic of the
genus Olea that the stereome
cells traverse the pneumatic
tissue in all directions (fig. 19).
The pericylic stereome is thick
walled only on the hadrome side
of the midrib; on the leptome
side it is thin walled with a very

few thick-walled cells interspersed. The collenchyma (PI. V, fig. 1) is
hypodermal above and below the midrib and extends to the pericycle;
it is generally thick walled, especially near the epidermis.

The mestome strands are, with the exception of the midrib (PI. V,
fig. 1), embedded in the chlorenchyma, and all the lateral strands
are surrounded by thin-walled parenchyma sheaths, sometimes with

a few adjoining stereome cells.
The midrib has no parenchyma
sheath and no endodermis, but, as
previously described, it is surround-
ed by a thick sheath of stereome.
All the mestome strands are col-
lateral. The leptome forms an
arch underneath the shorter but
broader arch of hadrome. In the
latter, each double row of vessels is
separated from the next by a single
row of parenchyma cells (parencliy-
matic ray).
The petiole, examined at the characteristic point (where the mes-
tome strands enter the leaf blade), shows a hemicylindric outline in
cross section. It is covered with shield-shaped hairs, as is the blade,
and the outer walls of the epidermis cells are extremely thick. The
cortex is a solid mass of collenchymatic tissue and contains an arch-
shaped collateral mestome strand in the center. This mestome

192 X

FiG. 19.— Pneumatic tissue of the dorsal side of a
blade traversed by stereome cells. From a leaf
of the Mission olive. (X 150.)

52 ANATOMICAL STKUCTUKE OF THE OLIVE.

strand has no support of stereome in the stricter sense of the word,
but is simply surrounded by a small collenchymatic tissue. Lep-
tome and hadrome show the same structure as in the midrib of the
blade.

The arrangement of the tissues of the stem is shown in Plate V,
figure 2. The cross section of the young twig is quadrangular and
/minutely four winged. The thin, smooth cuticle covers an epidermis
with hairs similar to those of the leaf, and the outer cell walls are
very thick; inside the epidermis are about twelve layers of cortical
parenchyma, collenchymatic in the peripheral layers but more thin
walled around the stele. Phellogen appears in the outermost layer
of the cortex and soon develops several layers of cork, of which about
three develop during the first summer. (Fig. 20.)

There is no endodermis, but a stereomatic and very thick-walled
pericycle surrounds the stele. This pericycle, however, is not con-
tinuous, but consists of many strands of
stereome separated by a few parenchy-
matic cells. The leptome presents a
circular zone bordering on the pericycle,
and is separated by cambium from the
^ ^^ hadrome. The vessels (the scalariform

^oOdor^^O^P^ ones especially) are thick walled and

"^Ooo^j-^^^QO ^°"' separated from each other by paren-
^ ^'^^-^ ^--^ chymatic rays, each of a single row of

Fig. 20.-Development of cork layers in rather tllin-Wallcd Cclls. The Cells of
thecortexof an olive stem. (X 150.)

the pith (which is solid) have thick
porous walls and contain much starch.

As compared with the preceding (the Mission variety from Niles,
Cal.), the unknown variety of olive of which material was collected
in the orchard at Phoenix, Ariz., is noteworthy for the extremely
thick-walled epidermis on both faces of the leaf; thick- walled collen-
chyma extending from the epidermis to the pericycle of the midrib;
more stereome in the pericycle; palisade and pneumatic tissues more
compact but containing less stereome. In the petiole all the tissues
are extremely thick walled. Cork develops very early in the stem,
since even in the apical internode there are seven layers. The epi-
dermis of the apical internode is extremely thick walled.

The two unidentified varieties collected in the abandoned orchard
at Palm Springs appear to be identical in anatomical structure.
From the variety growing at Phoenix they differ only in the much
narrower midrib.

192

LEAP AND STEM STEUCTUKE OF THE OLIVE. 53

To summarize: The leaf and stem structure of the ohve are such
as to protect it admirably against excessive loss of water by trans-
piration and hence adapt it to growing in very dry soils and climates.
The scanty evidence here presented would seem to indicate that the
considerable difference in aridity represented by the two environ-
ments at Niles (where the average yearly rainfall is 14.8 inches, where
moisture-laden winds blow in from the ocean, and where occasional
irrigation is given) and of Palm Springs (where the average yearly
rainfall is only 3.5 inches, where the air is excessively dry, and where
the trees had received no irrigation for seven years) has a distinct,
though comparatively slight, effect upon the anatomical structure
of this plant, for even at Niles the olive exhibits in a high degree the
characteristics of a xerophytic plant.

192

P L AT E S.

192

55

DESCRIPTION OF PLATES.

Plate I. Fig. 1. — One of the larger olive trees on the Bogart-Degolia plantation
near Casa Grande, Ariz. Fig. 2. — Olive trees in the "Las Palmas" section, near
Phoenix, Ariz., after six years of neglect and lack of water.

Plate II. Fig. 1.— View in the Florence, Ariz., olive grove, about 16 years old, which
has had no irrigation for the past six years. At the left, dead apricot and almond
trees of the same age; at the right, olive trees in vigorous condition. Fig. 2. —
Interior view in the grove shown in figure 1, showing a fine growth but thinner
foliage than in the outer row shown in figure 1, due to the crowding of the trees.

Plate III. Fig. 1. — Viewin the Pope olive plantation, near Palm Springs, Cal., after
six years of neglect. Mean annual rainfall only 3 J inches. Fig. 2. — One of the
larger trees, 8 feet high, in the Pope olive plantation, showing the low habit of
growth and the protection of the trunk and main branches from heat by a canopy
of foliage.

Plate IV. Fig. 1. — Characteristic burl at the base of an olive tree on the Pope olive
plantation, near Palm Springs, Cal. Fig. 2.— Feeding rootlets, natural size, from
6 inches in depth, on the same plantation shown in figure 1.

Plate V. Fig. 1. — Cross section of the midrib of the leaf of Olea europea (Mission
variety), showing the epidermis, palisade tissue, massively developed coUen-
chyma, pericyclic stereome, hadrome, leptome, and pneumatic tissue. Mag-
nified 180 times. Fig. 2. — Cross section of one of the apical internodes of the
stem, showing the epidermis, hypodermal collenchyma, stereome ring, leptome,
hadrome, and pith. Magnified 112 times.

Plate VI. Fig. 1. — View in a 500-acre olive plantation in southern Los Angeles
County, near La Mirada, Cal., grown without irrigation. The planting distance
of 20 feet each way is much too close for the full development of the trees.
Fig. 2. — View in a different part of the plantation shown in figure 1, where the
trees have been thinned by removing alternate diagonal rows. The conditions
are consequently much improved.
192
56

Bui. 192, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate I.

Fig. 1.— One of the Larger Olive Trees on the Bogart-
Degolia Plantation, near Gasa Grande, Ariz.

Fig. 2.— Olive Tree at "Las Palmas," near Phoenix, Ariz., After Six

Years of Neglect.

Bui. 192, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate II.

Bui. 192, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate III

Fig. 1.— View in the Pope Olive Plantation, near Palm Springs, Cal., After Six

Years of Neglect.

>

K

,

B^JH^KfllP

^

--

HR^i

^:

,

t

K

1/ .■' '■

-

Fig. 2.— One of the Larger Trees in the Pope Olive Plantation, Showing the
Low Habit of Growth of the Trees.

Bui. 192, Bureau of Plant Industry, U. S. Dept. of Agiiculture.

Plate IV.

Fig. 1 .—Characteristic Burl at the Base of an Olive Tree on the Pope Plan-
tation, NEAR Palm Springs, Cal.

■«^*'; i. j^

Fig. 2.— Feeding Rootlets, from 6 Inches in Depth, on the Pope Olive Plan-
tation. 'Natural Size.)

Bui. 192, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate V.

Coll.

Ep.

W~

1^ -I

■■;:-.; 'x'^^JU.

Ep:..(

;o-y^®oT)oOg^059^

^O-oo.

^\-'

m

Coll.- ■

Fig. 1.— Cross Section of the Midrib of the Leaf of Olea europea (Mission

Variety).

Coll.

..St.

-Cross Section of One of the Apical Internodes of the Stem of Olea
europea (Mission Variety).

Bui. 192, Bureau of Plant Industry, U. 5. Dept. of Agriculture.

Plate VI.

Fig. 1.— View in the 500-acre Olive Plantation near La Mirada, Cal.

Fig. 2.-VIEW in a Different Part of the Plantation Shown in Figure 1, where
THE Trees have been Thinned by Removing Alternate Diagonal Rows.

INDEX.

' Page.

Africa, olive culture 10, 13, 21-22, 37, 38, 41, 42,44

Algeria, factors relating to olive culture 13, 37, 38

Almond, behavior under arid conditions 15-16, 56

Altitude, relation to olive culture 10, 17, 19, 35-36

Appendix, anatomical structure of the olive 47-53

Apricot, cultivated, behavior under arid conditions 13, 15, 17, 18, 23, 42-43, 56

wild, adaptation to arid conditions 24

Arizona, climatic records 11-12, 36, 37-40, 50

olive culture 10, 17, 30, 33, 36-38, 39, 42

Asb, Arizona, behavior under arid conditions 13

Beaumont, Cal., dry-land olive culture 17, 31

Benson, Ariz., climatic record 36

Black scale. See Insects.

Boerne, Tex., altitude and temperatures 35

Bogart-Degolia olive grove. See Olive, abandoned grove at Casa Grande.
California Agricultural Experiment Station. See Soils, tests in California.

olive culture 10,17-27,29^3

State Board of Horticulture, report 34, 35, 36, 41

Caruso, G., on effect of temperature on the olive 37, 39, 40

Casa Grande, Ariz., dry-land olive culture 10-13, 15, 16, 20-23, 56

Cercidium torreyanum, adaptation to arid conditions 24

Chatsworth, Cal., dry-land olive culture 31

Chemlali olive. See Olive, varieties.

Chilopsis, adaptation to arid conditions 24

Climate, relation to olive culture. . 9, 10-13, 16, 18-19, 24-25, 31-32, 34-42,43-44, 50, 53

Cline, Ariz., climatic record 36

Colorado Desert, possibility of olive growing 38

Columbella olive. See Olive, varieties.

Columbia, Ariz., climatic record 36

Congress, Ariz., climatic record 36

Cottonwood, behavior under arid conditions 18, 25-26

Covillea tridenta, natural desert growth 18

Creosote bush. See Covillea tridenta.

Culture and neglect, contrast of effects 33, 56

Dalea spinosa, adaptation to arid conditions 24

Distance of planting. See Olive, trees, spacing in orchard.

Drought, power of resistance, factors of investigation 9-10, 43

Dry-land olive grove, abandoned. See Olive, abandoned grove.

Dudleyville, Ariz., climatic record 36

Emplectocladus, subgeneric name of wild apricot 24

Environment, effect upon modifications of structure 30, 43, 47-53

192 57

58 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

Page.

Fig, behavior under arid conditions 13, 18, 26, 42

Florence, Ariz., abandoned dry-land olive grove 15-16, 56

irrigation canal 13

Flowers. See Olive, flowers.

Foliage of the olive, browsing by live stock. See Stock, live.

Forage, use of foliage and twigs of the olive 13-14, 16

Fort Mcintosh, Tex., climatic record 34

Fort Ringgold, Tex., climatic record 34

France, factors relating to olive culture 19, 35, 43

P^axinus velutina, behavior under arid conditions 13

Fresno, Cal., climatic data ^ 35, 37, 39

Fruit. See Olive, fruit.

Gila River, diversion of water for irrigation 13

Globe, Ariz., climatic record 36

Grape, behavior under arid conditions 13, 18, 23, 42

Heat. See Temperature.

Hidalgo Tablada, Jose de, on factors of temperature in olive culture 34, 39, 40

Holm, Theodore, study of anatomy of leaf and stem 30, 47-53

Humidity, relative, relation to olive culture 11-12, 32

Insects, occurrence on the olive 33

Introduction to bulletin 9-10

Irrigation, relation to dry-land olive culture 10,

13, 15-18, 23, 24, 26, 27, 30, 32, 37, 38, 41, 42-44, 49-50, 53, 56

Italy, factors relating to olive culture 19, 34, 35, 37, 38, 39, 40, 43

Jerome, Ariz., climatic record 36

Jesunofsky, L. N., on rainfall at places in Arizona 11

Kearney, T. H., on features of dry-land olive culture 10, 13, 22, 41, 44

Kimball, F. A., on relation of water supply to successful olive culture 41

Kingman, Ariz., climatic record 36

La Mirada, Cal . , dry-land olive culture 31-32, 56

Las Palmas, dry-land olive grove in Arizona 16, 43, 56

Leaves of the olive. See Olive, anatomical structure.

Lelong, B. M., on cold endurance of the olive 34

Los Angeles, Cal., climatic features 31-32, 37, 39, 40

Manzanillo olive. See Olive, varieties.

Maricopa, Ariz., climatic records 11-12

Marvin, A. T., on climatic features 38, 39

Mason, S. C, collection of soil samples for analysis 20-22

Mesa, Ariz., climatic records 11-12

Mesquite, adaptation to arid conditions 12, 13, 14, 24, 27, 43

Mission olive. See Olive, varieties.

Moisture, conservation features. . . . 9-10, 14, 15, 16, 24-25, 26, 27-30, 33, 41, 43-44, 49, 53

Murray, Wellwood, irrigated garden at Palm Springs 26, 37

Nevadillo olive. See Olive, varieties.

Niles,.Cal., material obtained for study of structure 30, 50, 52, 53

Olea europea, anatomical structure 47-53, 56

Olive, abandoned grove at Casa Grande 10, 13-15, 43, 56

Palm Springs 17-27, 29, 43, 49-50, 52-53, 56

near Florence, Ariz 15-16, 43

Phoenix, Ariz 16-17, 49

adaptation to arid conditions 10, 13-15, 16, 24-25, 27-30, 43, 49-53

anatomical structure 30, 47-53, 56

192

INDEX. 59

Page.

Olive, competition with desert shrubs 14, 19

culture, at a distance from the seacoast 37

dry-land area in United States, limitations 34-42

in California 31-33

flowers, temperature requirements for development 26, 39, 40

fruit, factors in profitable production 9, 16, 17, 26, 33, 36-38, 40-42

leaves, roots, and stem. See Olive, anatomical structure.

root systems 9-10, 14, 15, 25, 27-30, 41-42, 43-44

trees, shape of top modified for desert life 13-14, 24

spacing in' orchard 9, 14, 23, 26-27, 32-33, 41-44, 56

varieties, Chemlali 34, 42, 44

Columbella 33

Manzanillo 25, 28, 29

Mission 33, 50, 52, 56

Nevadillo 33

Pendulina 33,37

xerophytic characters 13-14, 15, 16, 24, 27-30, 33, 37, 41, 43, 49-53, 56

See also Climate, Drought, Irrigation, Moisture, Pruning, Soils, and Weeds.

Oracle, Ariz., climatic record 36

Orange, demands upon soil 23

Oroville, Cal., dry-land olive culture 31

Palm, behavior under arid conditions 16, 24

Palm Springs, Cal., dry-land olive culture 17-27, 32, 37-38, 49-50, 52-53, 56

Palmdale, Cal., olive culture 18, 20

Paloverde, adaptation to arid conditions 24

Peach, growth in Michigan, comparison of soils 23

Pendulina olive. See Olive, varieties.

Pepper, behavior of tree under arid conditions 16, 18, 26

Phoenix, Ariz., climatic records 11-12, 37-39, 50

dry-land olive culture 16-17, 49, 52, 56

phenological records for the olive 39, 40

Plates, description 56

Plum, demands upon soil 23

Pomegranate, behavior under arid conditions 16

Pope olive plantation. See Olive, abandoned grove at Palm Springs.

Prune, behavior under arid and other conditions 13, 17

Pruning, methods under arid conditions 9, 13-14, 16, 24, 33

Prunus fremontii, adaptation to arid conditions 24

Quito, Ecuador, South America, growth of olive 36

Rainfall, relation to olive culture 9-12, 13, 19, 25, 31-32, 33, 40-42, 43, 44, 50, 53, 56

Relative-humidity. See Humidity, relative.

Roberts, I. P., on fertility of soils 23

Roots of the olive. See Olive, anatomical structure.

San Antonio, Tex., climatic data 34-35

San Carlos, Ariz., climatic record 36

San Diego, Cal., climatic data 30, 37, 39

San Fernando, Cal., dry-land olive culture 31

San Gorgonio Pass, relation to olive-culture projects 17, 18

San Jose, Cal., temperature data 37, 39, 40

Santa Barbara, Cal., temperature data 40

Santa Cruz River (Wash.), character of watercourse 12

Schinus molle, behavior under arid conditions .,.,,,., 18

J92

60 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES.

Page.

Seville, Spain, date of blossoming of olive 39

Sfax, Africa, factors relating to olive culture 21-22, 35, 37, 38

Sicily, factors relating to olive culture 36-38

Simmonds, P. L., on altitude of growth of olive at Quito 36

Smith, J. G., on analyses of soils. 22

Soils, analyses 20-23

relation to olive culture 9, 12, 13, 15, 16, 20-23, 27, 32, 33, 43

tests in California 23

Spacing of trees. See Olive, trees, spacing.

Spain, cultivation of olive 39

Stem of the olive. See Olive, anatomical structure.

Stock, live, relation of browsing habits to olive culture.'. 13-14, 15, 16

Summary of bulletin 42-44

Temperature, relation to olive culture 9-10, 16, 18-19, 24-25, 31, 33, 34^0, 43, 56

Texas, dry-land olive culture 34-35, 42

Tombstone, Ariz., climatic record 36

Topography, typical localities 12, 13, 17, 32

Trabut, L., on soils favorable to olive growth 22

Tucson, Ariz., climatic record 36, 37, 38, 39

Tunis, factors relating to olive culture 10, 35, 38, 42, 44

Underground water. See Water.

Varieties of the olive. See Olive, varieties.

Wallaber, A. B., on climatic data 32, 39

Washingtonia filifera, adaptation to arid conditions 24

Water, underground, relation to olive culture 12-13

Weather Bureau, on climatological data 32, 34, 36, 39, 40

Weeds, relation to olive culture 23, 33

Whitewater River, diversion of water for irrigation 18

192

o

(Continued from page 2 of cover.)

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148. Seeds and Plants Imported. Inventory No. 16. 1909. Price, 10 cents.

149. Diseases of Deciduous Forest Trees. 1909. Price, 15 cents.

150. Wild Alfalfas and Clovers of Siberia. 1909. Price, 10 cents.

151. Fruits Recommended for Cultivation. 1909. Price, 15 cents. ;;

152. The Loose Smuts of Barley and Wheat. 1909. Price, 15 cents. •;

153. Seeds and Plants Imported. Inventory No. 17. 1909. Price, 10 cents.

154. Farm Water Supplies of Minnesota. 1909. Price, 15 cents. s

155. The Control of Black-Rot of the Grape. 1909. Price, 15 cents. 1

156. A Study of Diversity in EgM)tian Cotton. 1909. Price, 15 cents.

157. The Truckee-Carson Experiment Farm. 1909. Price, 10 cents.

158. The Root-Rot of Tobacco Caused bv Thielavia Basicola. 1909. Price, 15 cents. ■

159. Local Adjustment of Cotton Varieties. 1909. Price, 10 cents. .;

160. Italian Lemons and Their By-Products. 1909. Price, 15 cents. ;
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162. Seeds and Plants Imported. Inventory No. 18. 1910. Price, 10 cents. ;

163. Varieties of American Upland Cotton. 1910. Price, 25 cents.

164. Promising Root Crops for the South. 1910. Price, 10 cents. ,„,„ t, . ,n ♦

165. Application of Some of the Principles of Heredity to Plant Breeding. 1910. Price, 10 cents.

166. The Mistletoe Pest in the Southwest. 1910. Price, 10 cents. j

167. New Methods of Plant Breeding. 1910. Price, 20 cents. ,

168. Seeds and Plants Imported. Inventory No. 19. 1909. Price, 5 cents. ;j

169. Variegated Alfalfa. 1910. Price, 10 cents.

170. Traction Plowine. 1910. Price, 10 cents. . or *

171. Some Fungous Diseases of Economic Importance. 1910. Price, 25 cents. !

172. Grape Investigations in Vinifera Regions. 1910. Price, 25 cents.

173. Seasonal Nitriflcation as Influenced by Crops and Tillage. 1910. Price, 10 cents. *

174. The Cx)ntrol of Peach Brown-Rot and Scab. 1910. Price, 10 cents. :

175. The Historv and Distribution of Sorghum. 1910. Price, 10 cents. •;

176. Seeds and Plants Imported. Inventory No. 20. 1910. Price, 5 cents.

177. A Protected Stock Range in Arizona. 1910. Price, 10 cents. i

178. Improvement of the Wheat Crop in California. 1910. Price, 10 cents. ;

179. The Florida Velvet Bean and Related Plants. 1910. Price, 10 cents.

180. Agricultural and Botanical Explorations in Palestine. 1910. Price, 15 cents.

181. The Curly-Top of Beets. 1910. Price, 15 cents. ,..„.,„ 4. '

182. Ten Years' Experience with the Swedish Select Oat. 1910. Price, 10 cents. :

183. Field Studies of the Crown-Gall of the Grape. 1910. Price 10 cents. x,,.^ m -

184. The Production of Vegetable Seeds: Sweet Corn and Garden Peas and Beans. 1910. Price, 10

Cents

185. Cold Resistance of Alfalfa and Some Factors Influencing it. 1910. Price, 15 cents. ;

186. Field Studies of the Crown-Gall and Hairy-Root of the Apple Tree. 1910. Price, —cents. ;

187. A Study of Cultivation Methods and Crop Rotation for the Great Plains Area. 1910. Price, 15 ,

cGnts

188. Dry Farming in Relation to Rainfall and Evaporation. 1910. Price, 15 cents. ,,,,.,,,. I
1.89. The Source of the Drug Dioscorea, with a Consideration of the Dioscorea Found in the Unilea ,

States. 1910. Price, — cents. \

190. Orchard Green-Manure Crops in California. 1910. Price, 10 cents. 1

191. The Value of First-Generation Hybrids In Corn. 1910. Price, 10 cents. i

192 ■

U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF PLANT INDUSTRY—BULLETIN NO. 193.

B. T. GALLOWAY, Chief of Bttreau.

EXPERIMENTS IN BLUEBERRY CULTURE.

BY

FREDERICK Y. COVILLE,
Botanist in Charge of Taxonomic and Range Investigations.

Issued NovEjrBRR 15, 1910.

WASHINGTON:

GOVERNMENT PRINTING OFFICE.
1910.

BULLETINS OF THE BUREAU OF PLANT INDUSTRY.

^

The scientific aud technical iniblications of tlic Bureau of Plant Industry, which was i

organized July 1, 1901, arc issued in a single series of bulletins, a list of which. follows. :

Attention is directed to the fact that the publications in this series are not for general i
distribution. The Superintendent of Documents, Government Printing Office, Washington, /i
I). C, is authorized by law to sell them at cost, and to him all applications for these bul- ]
letins should be made, accompanied by -a postal money order for the required amount or

by cash. Numbers omitted from this list can not be furnished. ^

No. 2. Spermatogenesis and Fecundation of Zamia. 1901. . TPrice,- 20 cents,
y. Macaroni Wheats. 1901. Price, 20 cents.

4. Range Improvement, in Arizona. I'JOl. Price, 10 cents. .i

8. A Collection of Fungi Prepared: for Distribution. 1902. Price, 10 cents. '
0. The North American Species of Spartiua. ' 1902. Price, 10 cents.- ,,

10. Records of Seed Distribution, etc. 1902. Price, 10 cents.

11. .lohnson Grass. 1902. Price, 10 cents. •;
IS. Range Improvement in Central Texas. 1902. Price, 10 cents. *■

14. The Decay of Timber and Methods of Preventing It. 1902. Price, .55 cents. *

15. Forage Conditions ^>n Northern Border of Great Basin. 1902. Pri'ce, 15 cents. i
17. Some Diseases of the Cowpea. 1902. I'rice, 10 cents. ,1
20. Manufacture of Semolina aud Macaroni. 1902. Price, 15 cents. i
22. Injurious Effects of Premature I'ollinktion. 1902. Pi'ice, 10 cents. '-i
2o. Berseem : The Great Forage and Soiling Crop of Nile Valley. 1902. Pi-ice, 15

cents. '

24. T'nfei-mented Grape Must. 1902. Price, 10 cents.

25. Miscellaneous I'apers. 1903. Price. 15 cents. ■
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29. The Effect of Black-Rot on Turnips. 1903. Price, 15 cents. ':

31. Cultivated Forage Crops of the Northwestern States. 1902. Pricey. 10. Cents.

32. .\ Disease of the White Ash. 1903. Rriee, 10 cents. : -■ "^ ' i

33. North American Species of Leptochloa. 1903. Price, 15 cents. ■ ',1
35. Itecent Foreign Explorations. 1903. Price, 15 cents; i

30. The "Bluing" of the Western Yellow Pine, etc. 1903. Price, 30 cents.

37. Formation of Spores in Sporangia of- Rhizopus N'lgricans. etc. 190.3. Price, 15 cents.

38. Forage Conditions in Eastern Washington, etc. 1903. Price, 15 cents. J

39. The Propagation of the Easter Lily from Seed. 1903. Price, 10 cents.

41. The Commercial Grading of Corn. 1903. -Price, 10 cents. '

42. Three New Plant Introductions from Japan. 1903. Price, 10 cents. ■■'.^

47. The Description of Wheat Varieties. 1903. Price, 10 cents. ,

48. The Apple in Cold Storage. 1903." Price, 15 cents. '- 1

49. Culture' of the Central American Rubber Ti;ee. 1903. Price, 25 cents. '

50. Wild Rice : Its Uses and Propagation. 1903. Price, 10 cents. ]

51. Miscellaneous Papers. 1005. Price. 5 cents. ;
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59. Pasture, Meadow, and Forage Crops in Nebraska.' 1904. Price, 10 cents. j

00. -V Soft Rot of the Calhi Lily. 1904. Price, 10 cents. . -

61. The Avocado in Florida. 1D04. Price, -5 cents. . ,

62. Notes on Egyptian Agriculture. 1904. Price, 10 'cents. ■'

67. Range Invosllgations in .irizona. 1904. Price. 15 cents. \

68. North American Species of .\gr6stis. 1905. I'rice. 10 cents. '

69. American Varieties of Lettuce. 1904. Price, 15 cents.

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71. Soil Inoculation for Legumes. 1905. Price, 15 cents. ;

72. Miscellaneous I'apers. 1905. Price. 5 cents. j

73. The Development of Single-Germ Beet "Seed. 1905. Price, 10 cents.

74. I'rickly Pear and Other Cacti as Food for Stock. 1905. I*i-rce, 5 cents. ;

75. Range Management in the State of Washington. 1905. I'rice. 5, cents. .•

76. Copper as an Algicide and Disinfectant in Water Supplies. 1905. Price, .5 cents. , ,;

77. The .\vocado : .V Salad Fruit from the Ti-opics. 1905. Price, 5 cents. ' 'J

79. Variability of Wheat Varieties In Resistance to Toxic Salts. 1905. Price, 5 cents, "v

80. Agricultural Explorations in Algeria. 1905. Price, 10 cents. j

81. Evolution of Cellular Structures. 1905. Price', 5 cents. -

82. (irass Lands of the South Alaska Coast. 1905. Price, 10 Gen;ts. 1

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85. Principles of Mushroom Growing and Spawn Making. 1905. Price, 10 cents. i

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89. Wild Medicinal Plants of the United States. 1906. PWce, 5 cents.

90. Miscellaneous Papers. 1906. Price, 5 cents. '■ • ;

91. Varieties of Tobacco Seed Distributed, etc. 1900.* Price, 5 cents. .;

94. I'^arra Practice with Forage Crops in Western Oregon, etc. 190G. I'rice, 10 cents. '

95. .\ New Type of Red Clover. 1906. Price, 10 cents. !

96. Tobacco Breeding. 1907. Price. L5 cents. .

97. Seeds and Plants Imported. Inventory No. 11. 1907. Price, 15 cents. ^

98. Soy Bean Varieties. 1907. I'rice, 15 cents. i

99. Quick .Method for Determination of Moisture in Grain. 1007. Price, 5 cents. ^
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102. Miscellaneous Papers. 1907, Price, 15 cents. -
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104. The I^se of Feldspathic Rocks as Fertilizers. 1907. Price, 5 cents. '■

105. Relation of I'omposition of Leaf to Burning of Tobacco. 1907. Price, 10 eenls. J

106. Seeds and I'lants Imported. Inventory No. 12. 1907. I'rice, 15 cents. . :

[Continued on page 3 of cover.] •/

193 J

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 193.

B. T. GALLOWAY, Chief of Bureau.

EXPERIMENTS IN BLUEBERRY CULTURE.

BY

FREDERICK V. COVILLE,
Botanist in Charge of Taxonomic and Range Investigations.

Issued Xove-M1',ek .15, 1910.

LIBRARY
NEW YORK
BOTANICAL

GARDEN.

WASHINGTON:

government printing office.

1910.

BUREAU OF PLANT INDUSTRY.

193
2

Chief of Bureau, Beverly T. Galloway.
Assistant Chief of Bureau, G. Harold Powell.
Editor, J. E. Rockwell.
Chief Clerk, James E. Jones.

Taxoxomic and Range Ixvestioations.

SCIEXTIFIC staff.

Frederick V. Coville, Botanist in Charge.
A. S. Hitchcock, Systematic A(jrostolo(jist.
W. F. Wight, Botanist.

A. H. Moore and P. L. Ricker, Assistant Botanii
W. E. SaCford, Assistant Curator.
Agnes Chase, Assistant.
E. L. Greene, Expert.

LETTER OF TRANSMITTAL

U. S. Department of Agriculture,

Bureau of Plant Industry,

Office of the Chief,
Washington, D. C, July 19, 1910.

Sir : I have the honor to transmit herewith and to recommend for
publication as Bulletin No, 193 of the series of this Bureau a manu-
script by Mr. Frederick V. Coville, Botanist in Charge of Taxonomic
and Range Investigations, entitled " Experiments in Blueberry Cul-
ture." Mr. Coville has found by experiment how blueberries differ
from ordinary plants in their method of nutrition and in their soil
requirements, and by means of this knowledge he has worked out a
system of pot culture under which these plants attain a development
beyond all previous expectations. There is good prospect that the
application of the knowledge thus gained will establish the blue-
berry in field culture and that ultimately improved varieties of these
plants will be grov>'n successfully on a commercial scale.

A particularly interesting and significant feature of these experi-
ments is the light they shed on the possible utilization of the natu-
rally acid lands that occupy extensive areas in the eastern United
States. These lands are generally valued at a low price, and the
chief expense involved in their utilization for ordinary agricultural
crops is the cost of correcting their acidity and its effects by liming,
fertilizing, and cultural manipulation. The question presents itself,
'' May we not more effectively utilize such lands by growing on them
crops which, like the blueberry, thrive in acid soils ? "

Some of the experimental methods and equipment utilized by Mr.
Coville are commended to other plant experimenters, especially the
use of darkened and drained glass pots for the intimate observation
of the behavior of roots, and the plunging of pots in moist sand to
maintain equable moisture and aeration conditions.
Respectfully,

Wm. a. Taylor,
Acting Chief of Bureau.

Hon. James "Wilson,

Secretary of Agriculture.

193 3

CONTENTS.

Page.
Introduction 11

Peculiarities of growth in the blueberry plant 14

Soil requirements 14

(1) The swamp blueberry does not thrive in a rich garden soil of the

ordinary type 14

(2) The swamp blueberry does not thrive in a heavily manured soil . 17

(3) The swamp blueberry does not thrive in a soil made sweet by

lime 19

(4) The swamp blueberry does not thrive in a heavy clay soil 24

(5) The swamp blueberry does not thrive in a thoroughly decomposed

leaf mold, such as has a neutral reaction 24

(6) The swamp blueberry does not thrive in soils having a neutral or

alkaline reaction, but for vigorous growth it requires an acid

soil 26

(7) The favorite type of acid soil for the swamp blueberry is peat. . . 31

(8) Peat suitable for the swamp blueberry may be found either in

bogs or on the surface of the ground in sandy oak or pine woods. 32

(9) For active growth the swamp blueberry requires a well-aerated

soil. Conversely, the swamp blueberry does not continue in
active growth in a soil saturated with water 35

(10) Aeration conditions satisfactory for the swamp blueberry are

prevalent in sandy soils 36

(11) Aeration conditions satisfactory for the swamp blueberry are

found in drained fibrous peat 37

(12) Aeration conditions satisfactory for the swamp blueberry are

found in masses of live, moist, but not submerged, sphagnum.. 38
Peculiarities of nutrition 40

(13) The swamp blueberry is devoid of root hairs, the minute organs

through which the ordinary plants of agriculture absorb their
moisture and food 40

(14) The rootlets of healthy plants of the swamp blueberry are in-

habited by a fungus, of the sort known technically as an endo-
trophic mycorrhiza 42

(15) The mycorrhizal fungus of the swamp blueberry appears to have

no injurious effect, but rather a beneficial effect, upon the
blueberry plant 44

(16) The acid peaty soils in which the swamp blueberry thrives are

deficient in "available" nitrogen, although containing large
amounts of "nonavailable" nitrogen 45

(17) The deficiency of available nitrogen in the acid peaty soil in

which the swamp blueberry grows best is due to the inability
of the nitrifying bacteria to thrive in such a soil because of its

acidity 46

193 5

CONTENTS.

Peculiarities of growth in the blueberry plant — Continued.
Peculiarities of nutrition — Continued.

Page.

(18

(19

A method o

(20

(21
(22
(23
(24

(25

(26

(27

(28

(29

(30
(31

(32

(33

(34

(35
(36

193

From the evidence at hand the presumption is that the mycor-
rhizal fungus of the swamp blueberry transsforms the nonavail-
able nitrogen of peaty soils into a form of nitrogen available
for the nourishment of the blueberry plant 48

It is possible that the mycorrhizal fungus of the swamp blue-
berry transforms the free nitrogen of the atmosphere into a
form of nitrogen suited to the use of the blueberry plant 48

pot culture 51

Seeds of the swamp blueberry sown in August from fresli berries
germinate in about 5 weeks 51

The seedlings are first transplanted at the age of about 6 weeks,

when they are approaching an inch in height 54

When about 10 weeks old and nearly 2 inches in height the
seedlings begin to send out basal branches 57

When the seedlings are about 4 months old and about 3 inches
in height the growth of the original stem terminates 58

When the plants are about 5 months old and 4 to 6 inches in
height they are potted in 4-inch pots in the best peat or peat
mixture - - - 59

Blueberry plants potted in peat may be made to grow more rap-
idly if they are watered occasionally during the growing season
with water from a manure pit 62

Pots containing blueberry plants should be plunged in sand or
other material that will furnish constant moisture and good
aeration 65

Plants of the swamp blueberry sometimes lay down flowering
buds at the age of 7 months 67

In the spring after the danger of frost was past the plants were
repotted and placed out of doors, in half shade, plunged in
sand 67

By the use of the cultural methods already described, seedlings
of the swamp blueberry have been grown into robust plants
of a maximum height of 27 inches at 12 months from germi-
nation 68

The flowering buds of the blueberry are produced l)y the trans-
formation of dormant leaf buds in the latter part of the season . 71

At the end of their first year 70 per cent of the blueberry plants
had laid down flowering buds for the next spring's blossoming. 73

Plants of the swamp blueberry are exceedingly hardy and pass
the winter in good condition outdoors when the soil is covered
merely with an oak-leaf mulch, but when not exposed to out-
door conditions they do not begin their growth in spring in a
normal manner 74

Dormant plants make their early spring twig growth before new
roots begin to develop 76

Unless pollinated by an outside agency, such as insects, the
flowers produce little or no fruit 76

The fruit matures about 2 months after the flowering 78

So far as observed, the swamp blueberry when grown in acid
soils is little subject to fungous diseases or insect pests 79

CONTENTS. 7

* Page.

Improvement and propagation 80

(37) The parent plant of the swamp blueberry seedlings, the culture

of which has been described, bore berries over half an inch in
diameter 80

(38) There is every reason to believe that the blueberry can be

improved by breeding and by selection 82

(39) The swamp blueberry has b?en propagated by grafting, by bud-

ding, by layering, by twig cuttings, and by root cuttings 83

(•10) The most desirable method of propagating the swamp blueberry

is by cuttings 84

Field culture 86

(41) Experiments have been begun in the field culture of the swamp

blueberry - 86

Conclusion -■ 88

Index 91

193

ILLUSTRATIONS

PLATES.

Page.
Plate I. Fio. 1. — Root growth of a blueberry plant in clay mulched with

leaves. Fig. 2. — Root growth of a blueberry plant in peat 24

II. Blueberry seedlings in peat and leaf mold 26

III. Fig. 1.— Formation of kalmia peat, top layer. Fig. 2.— Formation

of kalmia peat, second layer 34

IV. Fig. 1.— Formation of kalmia peat, third layer. Fig. 2.— Formation

of kalmia peat, fourth layer - - - 34

V. Fig. 1.— Formation of kalmia peat, fifth layer. Fig. 2.— Formation

of kalmia peat, sixth layer 34

VI. Fig. 1. — Swamp blueberries from the parent bush of the seedlings of

1908. Fig. 2. — Seeds of the swamp blueberry 52

VII. Blueberry seedling four and a half months old 60

VIII. Cold frames containing one-year-old blueberry seedlings 68

IX. Large one-year-old seedlings of the swamp blueberry 70

X. Fig. 1. — Flow'eringbudsandleaf buds on blueberry twigs. Fig. 2. —
Flowering buds on a blueberry cutting. Fig. 3. — Flowering buds

on blueberry cuttings 72

XI. Yearling blueberry plant with 42 flowering buds 74

XII. Fig. 1. — Blueberry plant which was wintered indoors beginning
growth in the spring. Fig. 2.— Blueberry plant which w'as win-
tered outdoors beginning growth in the spring 76

XIII. Fig. 1. — Blueberry plant which was wintered indoors continuing

growth in the spring. Fig. 2. — Blueberry plant which was win-
tered outdoors continuing growth in the spring 76

XIV. Irregular flowering of a blueberry plant wintered indoors 78

XV. Berry ripened on a blueberry seedling at the age of 19 months 80

XVI. Fig. 1. — Grafted blueberry. Fig. 2. — Blueberry seedling success-
fully budded 84

XVII. Blueberry plants from twig cuttings 86

XVIII. Blueberry plant from a twig cutting 88

TEXT FIGURES.

Fig. 1. Rose cutting in rich garden soil 16

2. Rose cutting in peat mixture 16

3. Alfalfa seedlings in rich garden soil 17

4. Alfalfa seedlings in peat mixture 17

5. Blueberry seedling in rich garden soil 18

6. Blueberry seedling in peat mixture 18

7. Blueberry seedling in peat mixture limed » 23

8. Blueberry seedling in peat mixture unlimed 23

9. Blueberry seedling fed with alkaline nutrient solution 30

10. Blueberry seedling fed with acid nutrient solution 31

193 9

10 ILLUSTRATIONS.

Page.

Fig. 11. Root of a wheat plant, showing the root hairs 40

12. Portion of a wheat root, with root hairs 40

13. Tip of the root hair of a wheat plant 40

14. Root of a blueberry plant 41

15. Root of a blueberry plant, enlarged 41

16. Blueberry rootlet 41

17. Mycorrhizal fungus of a blueberry plant densely crowded in two

epidermal cells of the root 43

18. Mycorrhizal fungus of Kalmia latifolia in an epiilermal cell of the root. 44

19. Section of a blueberry seed 53

20. Blueberry seedlings in the cotyledon stage 53

21. Blueberry seedling about 6 weeks old, with five foliage leaves 54

22. Normal tip of stem in a blueberry seedling 57

23. Bract and young leaf at the end of the original stem in a blueberry

seedling 58

24. Blueberry seedling with diffuse type of branching 59

25. Blueberry seedling of the type with few branches 59

26. Spores of a supposedly injurious fungus in the epidermal cells of blue-

berry roots 64

27. Flowers of the blueberry, from 1908 seedlings of the large-berried

New Hampshire bush of Vaccinium corymbosum 77

28. Stamens of the blueberry 77

29. Compound pollen grain of the blueberry 78

30. Pistil and calyx of the blueberry, sh6wing the style and stigma 78

31. Blueberry plant grown from a root cutting 86

193

B. P. I. — 598.

EXPERIMENTS IN BLUEBERRY CULTURE.

INTHODUCTION.

In the grounds of the Smithsonian Institution at Washington are
two blueberry bushes of large size and great age. The taller is about
9 feet high. The largest stem is nearly 3 inches in diameter. It is
known that these bushes were growing prior to 1871, thirty-nine years
ago, and all the evidence indicates that they were planted at a much
earlier date. They are probably over 50 years old." In the Arnold
Arboretum, near Boston, are many blueberry bushes 30 years old
or more, grown from the seed by Mr. Jackson Dawson or trans-
planted from their wild habitats prior to 1880.

The two cases here cited demonstrate the fallacy of the popular
idea that the blueberry can not be transplanted or cultivated. This
idea rests on the unsuccessful experience of those who have taken up
Avild bushes and set them in a rich, well-manured garden soil. These
are exactly the conditions, as shown by experiments described in this
publication, under which blueberry plants become feeble and unpro-
ductive.

Four agricultural experiment stations, those of Maine, Rhode
Island, New York, and Michigan, have attempted to grow the blue-
berry as a fruit, but none of these attempts has resulted in the com-
mercial success of blueberry culture, and the experimental results
have been chiefly of a negative character. This outcome appeiirs to
have been due to a misunderstanding of the soil requirements of the
blueberry, which, as will be shown later, are radically different from
those of our common cultivated plants.

"The plants are Vaccinium atrococcum, a species closely related to Vaccinium
corymhosum, the well-known swamp or high bnsh blueberry of the Northern
States. In a list of the trees and shrubs of the Smithsonian crrounds prepared
by Arthur Schott in 1871, these bushes are included, but identified, however,
as Vaccinium fuscatum. The late Mr. George H. Brown, for more than a gen-
eration the superintendent of planting in the parks of Washington, also as-
sured the writer that these plants were not set out since he first became
responsible for the Smithsonian grounds, in 1871. The present plan of the
grounds was made by Mr. Andrew J. Downing, but the actual planting was not
done until after his death, in 1S52. It is possible that tlie I)lueberry bushes
may have been set out as early as 1848, in which year a partial planting of the
Smithsonian grounds was made by Mr. John Douglass.

193 " 11

12

EXPEEIMENTS IN BLUEBEEEY CULTURE.

In the Boston market there is a wide variation in the wholesale
price of blueberries. Shipments begin in early June from North
Carolina, followed in the latter part of the month by blueberries from
Pennsylvania, New Jersey, and New York. In early July, or in
some years in the last days of June, Massachusetts and New Hamp-
shire shii^ments begin to arrive, succeeded in late July or early
August by berries from Maine, Nova Scotia, and New Brunswick.
Receipts from these last two localities continue until late September.
The blueberries that bring the highest price are those from Massa-
chusetts and New Hampshire. At the time when other berries are
selling at 8 to 15 cents per quart wholesale, the first shipments of
New Hampshire berries often bring 20 to 23 cents.

The owner of a blueberry pasture in southern New Hampshire
who superintended the picking of his own berries and shipped
them to one of the secondary New England cities has courteously
shown his shipment records, from which the following data have
been compiled :

Records of shipments from a blnchcrry pasture in southern New Hampsliire,

1905-1909.

Year.

Date of shipment.

Total
ship-
ments.

Highest and
lowest price
per quart, a

Average

price per

quart, a

1905

July 1 to Aug. 14

July 17 to Aug. 15

July 20 to Aug. 15....

June 29 to Aug. 15

July 15 to Aug. 16....

Quarts.
2,233

2,756
2,538
3,602
1,255

Cents.
12i to 8

15 to 8
141 to 11

16 to 9i
14 to 9

Cents.
10 7

1906

9.6

1907

12 2

1908

10 8

1909

10 7

« This is the net price that the shipper received after deducting express charges.

The average net price for the five years was 10.8 cents per quart.
The record indicates the substantial returns that are secured from
ordinary wild berries picked and sent to market in rather better than
ordinary condition.

That the market would gladly pay a high price for a cultivated
blueberry of superior quality there can be no doubt. From the
market standpoint the features of superiority in a blueberry are large
size; light-blue color, due to the presence of a dense bloom over the
dark-purple or almost black skin ; " dryness," or freedom from super-
ficial moisture, especially the fermenting juice of broken berries;
and plumpness, that is, freedom from the withered or wrinkled ap-
pearance that the berries begin to acquire several days after picking.
While the connoisseur in blueberries who picks his own fruit knows
the widely varying flavors in the berries of different bushes, the buyer
in the city market is content to select his fruit according to its ap-
pearance, knowing that the flavor will be good enough in any event.

193

THE PICKING OF BLUEBEEEIES. 13

The size of the seed gives the buyer in New Enghmd markets very
little concern, for there the name blueberry is restricted to plants of
the genus Vaccinium, all of which have seeds so small as to be unno-
ticeable when the berry is eaten, while the name huckleberry is applied
with nearly the same precision to the species of the genus Gaj'lus-
sacia, in wliich the seed is surrounded b}^ a bony covering like a
minute peach pit, which crackles between the teeth. In southern cities
the fruits of both Vaccinium and Gaylussacia are called huckleberries,
and it is i^robable that the low estimation in which the fruit of Vac-
cinium is there held is largely due to the lack of a distinctive popular
name. To distinguish the two berries by their appearance is difficult
for any but an expert, for while huckleberries are mostly black and
blueberries mostly blue, some of the blueberries, or species of Vac-
cinium, are black, and some of the huckleberries are blue, notably
Gaylussacia frondosa., a species often abundant in the sandy soils of
the Atlantic Coastal Plain, which has a large, handsome berry of a
beautiful light-blue color and passable flavor, but with the disagree-
ably crackling seed pits characteristic of the other true huckleberries.

The blueberry withstands the rough treatment incident to ship-
ment so much better than most other berries that with proper han-
dling it should always reach the market in first-class condition.
But its good shipping qualities are often abused, and the fruit not
infrequently is exposed for sale partly crushed and the berries cov-
ered with soured juice and made further olfensive by the presence of
flies. This is the prevailing condition of blueberries and huckle-
berries in the markets of Washington, in striking contrast with the
dry, plump berries of the Boston market. This bad condition is due
usually to improper picking.

The small size of the blueberry, compared with other berries, ren-
ders the picking of it expensive. The owners of blueberry pastures
commonly pay two-thirds the net price of the berries to their pickers.
In order to reduce the cost of picking, various devices have been
employed. The most widely used of these is an implement known
as a blueberry rake, a scoop shaped somewhat like a deep dustpan,
provided in front with a series of long, pointed fingers of heavy wire.
With this implement an ordinary picker in the blueberry canning
districts of Maine, for example, gathers 3 to 5 bushels a day, for
which he receives If to 2 cents per quart. Blueberries can be picked
with a rake at about a fourth the cost of picking by hand. For this
reason many of the berries that go to market are picked with a
rake, and it is these berries Avhich, broken and fermenting, make
up the greater part of the low-grade stock so otfensive to the eye
and the taste. Blueberries intended for the market should never be
picked with a rake.

193

14 EXPEEIMENTS IN BLUEBEREY CULTURE.

AVliat has been said regarding the high cost of picking ordinary
bhieberries by hand indicates the importance of securing a berry of
large size if the plant is to be cultivated. Large size and abundance
mean a great reduction in the cost of picking. Large size means
also a higher market price, and when taken in connection with good
color and good market condition it means a much higher price.

The writer's interest was attracted to the subject of blueberry cul-
ture in 1906. In the autumn of that year some experiments were
made for him by Mr. George W. Oliver to ascertain a suitable method
of wrminatine: the seeds. In the autumn of 1907 special cultural ex-
periments were taken up. In 1908 experiments were begiui in the
propagation of bushes bearing berries of large size, the most satis-
factory of these being a Xew Hampshire bush of the swamp blueberry
{Vaccinium corymbosum) having berries a little more than half an
inch in diameter. The largest berries tried, a little more than five-
eighths of an inch in diameter, were from Oregon bushes of Vac-
cinium membranaceum. Except where otherwise stated, the experi-
ments described in this paper were made with Yaccinium corym-
hosurw. The principal results of the experiments are given under
brief numbered statements, each followed by a detailed explanation.

PECULIARITIES OF GROWTH IN THE BLUEBERRY PLANT.

SOIL REQUIREMENTS.

(1) The swamp blueberry does not thrive in a rich garden soil of the
ordinary type.

Although the statement just made might well rest on the direct
observation of experimenters who have failed to make blueberries
grow luxuriantly, or sometimes even remain alive, in rich garden
soils, nevertheless the citation of one of the writer's experiments may
serve to accentuate the fact. The soil chosen for the purpose was the
one used at the United States Department of Agriculture for grow-
ing roses. A sample of this soil, as mixed by the rose gardener, con-
sisted, according to his specifications, of " five shovelfuls of loam, one
shovelful of cow manure, and a handful of lime." The loam used
was a rotted grass turf grown on a rather clayey soil. The cow
manure was well rotted, having lain in the pile for several months,
with almost no admixture of straw. The lime was of the ordinary
air-slaked sort.

The pots used in the experimei*t were of glass, small 5-ounce drink-
ing glasses, about 2 inches in diameter at the bottom, 2^ at the top,
and 25 inches deep. A small hole bored through the bottom gave the
necessary drainage to the soil in the pot. Since the walls of these
pots were transparent, the normal growth of the roots and the pre-

193

THE USE OF GLASS POTS. 15

vention of an obscuring green growth of microscopic algse required
some arrangement for keeping the light away. This was accom-
plished either by sinking, or, as gardeners say, " plunging," the pots
nearly to the rim in sand, moss, or soil, or, when the pots were not
plunged, by fitting closely to the outside of each a removable cuff, as
it were, made of the opaque gray blotting paper used in pressing
specimens of plants. The use of a pot with transparent walls was
found to be of very great importance in the study of these plants, for
plants identical in appearance so far as the parts above ground were
concerned sometimes showed the most pronounced differences in the
growth and behavior of the roots, differences which otherwise would
not have been observed but which were in reality responsible for the
conspicuous changes that later took place in the growth of the stems
and leaves. The use of such glass pots, drained and darkened, is
strongly recommended to plant experimenters who use pot cultures,
as they afford a means of acquiring easily an intimate knowledge of
the great variations in the behavior of the feeding organs, the roots,
under different conditions.

On December 22, 1908, six glass pots were filled with the garden
soil described above, and a seedling blueberry about an inch in height
was transplanted into each. The seed bed from which the seedlings
were taken had been allowed to become partially dry before the
transplanting was done. In this condition there was no difficulty in
removing all of the sandy soil adhering to the roots of a seedling, so
that after it was transplanted it must derive its soil nourishment
from the new soil exclusively. In potting, the roots of the plant
were laid against the glass on one side of the pot so that their
behavior could be observed from the very first.

A transplanting of six other plants was then made, similar in all
respects to the first except that the soil used was a peat mixture known
from earlier experiments to be productive of vigorous growth in
blueberry plants. The exact character of this soil will be discussed
later in this publication.

This peaty blueberry soil is ill suited to the growth of ordinary
plants, while in the garden soil ordinary plants flourish luxuriantly.
In order to bring out this fact clearly by an experiment six glass pots
containing this garden soil were planted with five alfalfa seeds each,
and six more with one rooted rose cutting each. An identical
planting was made in twelve pots of blueberry soil.

Average examples of the growth that took place in these plantings
are shown in figures 1 to 6, reproduced from drawings carefully made
from actual photographs. In the garden soil the rooted rose cut-
ting, which was of the variety known as Cardinal, made vigorous
growth of both root and stem, and in forty-four days, when the

193

16

EXPERIMENTS IN BLUEBERRY CULTURE.

photograph was taken, had about quadrupled its leaf surface. In the
blueberr}^ soil the cutting was barely alive, the roots it had at the
time it was potted were nearly all dead, no new stem growth had been
made, and the leaflets it bore were only those still persisting from
the parent plant.

The alfalfa seeds began to germinate in both soils in three days.
At the end of a week a distinct difference in the color of the plants
was discernible. In the blueberry soil the seed leaves were darker
green in color, the midrib, which shows on the back of the leaf, was

Fir.. 1. — Rose cutting in rich garden soil.
(One-lialf natural size.)

Fig. 2. — Rose cutting in peat mix-
ture. (One-half natural size.)

purple, the stem was purple, and in some of the seed leaves the whole
under surface was purple. In the garden soil the seed leaves were
lighter green in color, and in only a few were the stems, and in still
fewer the midribs, somewhat purplish. At the end of forty-four days,
when the photographs reproduced in figures 3 and 4 were taken, the
alfalfa plants in the garden soil were 3 inches in height and vigorous,
Avhile the soil was crowded with roots on which nitrogen tubercles
had already begun to develop. In the blueberry soil the plants were
small leaved and sickly, about a third the height of the others, and

193

INJURIOUS EFFECTS OF RICH GARDEN SOIL.

17

the roots though long were slender and otherwise weak and bore no
tubercles.

In the case of the blueberry plants the relative growth in the two
soils took exactly the opposite course. At the end of the first week new
root growth had begun in all the pots containing blueberry soil, while
in those containing garden soil new root growth was apparent in only
one. At the end of forty-four days vigorous root growth had taken
place in the blueberry soil pots, and stem growth, which had been
interrupted at the time of transplanting, was well under way again.
In the garden soil, however, almost no root growth Avas discernible,
the old leaves were strongly purpled and stem and leaf growth had
not been resumed. Little attention was paid to these cultures during
the summer of 1909, but the relative condition of the two is fairly

Fig. 3. — Alfalfa seedlinjrs in rich garden soil.
(Oue-lialf natural size.)

Fig. 4.

-Alfalfa seedlings in peat mixture.
(One-half natural size.)

illustrated in figures 5 and G, from photographs taken November 22,
1909, after the leaves had fallen. The garden-soil pot contained only
a few stray roots, and the slender stems were only 2 inches high.
The pot containing blueberry soil was filled with a dense mass of
roots, and although the plant had not been repotted when it needed
repotting, the largest stem was nevertheless 11 inches long and the
weight of that part of the plant above ground was fifty-one times
that of the corresponding part of the garden-soil plant.

(2) The swamp blueberry does not thrive in a heavily manured soil.

In May, 1909, two healthy and vigorous blueberry seedlings were

sent for trial to one of the agricultural experiment stations. They

were set out in a soil that was known to be suitable for these plants,

for old blueberry bushes had been growing there for several years.

54708°— Bull. 193—10 2

18

EXPERIMENTS IN BLUEBERRY CULTURE.

The man who put the bhieberry seedlings in
the ground, however, misunderstanding the
directions sent him, filled in the holes in which
he set the plants with alternate layers of soil
and Avell-rotted stable manure. The writer ex-
amined the plants on August 27, 1900. when
they should have been either growing vigor-
ously or, with mature foliage, ripening their
Avood for the winter. Instead they had lost
nearly all their older leaves though still main-
taining a feeble and spindling growth at the
ends of the larger stems. The adjacent old
bushes growing in precisely the same soil, ex-
cept that it had not received the heavy appli-
cation of manure, bore at the same time vigor-
ous dark-green foliage and were ripening the
wood of their stout twigs and laying down
their flowering buds for the following year.
The manured plants when dug up and exam-
ined showed no new root growth whatever in
the manured soil outside the old earth ball, and
most of the roots on the surface of the ball
itself were dead.

Another experiment may be cited to show
the injurious eifect of heavy manuring. On
December 22, 1908, six blueberry seedlings were
transplanted into as many glass pots in a good
blueberry soil, and six
other seedlings w^ere
potted in the same
manner, except that to
each two parts of blue-
berry soil one part of
well-rotted but un-
leached cow manure
was added. At first
the manured plants
appeared, superficially,
to be doing better than
those not manured, for
in the former the pro-
duction of ncAv leaves
and the continued
growth of the stem tip

193

f¥^\M^::-'

D

Fig. 5. — Bhieherry seedling
in rich garden soil. (One-
half natural size.)

//

Fig. 0. — Blnolu'rry seedling
in peat mixture. (One-
half natural size.)

BLUEBEREIES WANTING IN LIMESTONE SOILS. 19

were not interrupted by the potting, while in the plants not mamired
there was a temporary but definite stopping of stem growth imme-
diately after the potting. The apparent superiority of growth in the
manured plants, above ground, continued for about three weeks. Be-
low ground, the roots of the two cultures shoAved directly opposite
results. In the plants without manure, new root growth began a few
dnjs after potting. At the end of three weeks the development of an
extensive root system was well under way and the plants were nearly
ready for a period of vigorous stem growth. In the manured plants,
however, either no root groAvth took place or only a slight amount,
the new rootlets being fewer, shorter, and stouter than in normal
plants. The old rootlets turned brown and appeared to be dead or
dying. (See p. 64.) At the end of five weeks the growth of the
tops was very sIoav. About ten days later, on February 6, a bright
Avarm day, the loAver lea\'es on three plants Avithered, and Avithin a
feAv Aveeks all six of the manured plants Avere dead.

(3) The swamp blueberry does not thrive in a soil made sweet by lime.

In its natural distribution the blueberry, like almost all plants
of this and the heather family, aA'oids limestone soils. The fertile
limestone areas of western Xew York, of Ohio, of Kentuclns and
of Tennessee lack the blueberry, the huckleberry, the laurel {Kalmia
JatifoUa), and the trailing arbutus {Epigaea repens). The State
of Alabama, as described by Charles Mohr in volume 6 of Contri-
butions from the United States National Herbarium, is traversed
from east to west in the general latitude of Montgomerj^ by a strip
of dark calcareous soil, 35 to 45 miles in Avidth, the so-called " black
belt," Avhich constitutes the great agricultural region of the State.
The noncalcareous areas north and south of this strip have in their
forests a characteristic undergrowth of blueberries and closely re-
lated plants, including huckleberries, farkleberries, and deerberries.
In the intermediate belt of black limestone soil, just described, the
plants of blueberry relationship are almost wholly wanting.

In an article entitled " The Soil Preferences of Certain Alpine
and Subalpine Plants," "' Mr. M. L. Fernald discusses the natural
distribution of over 250 species of plants found in the cold parts
of the northeastern United States and Canada. All the blueberries
he enumerates, five species, avoided calcareous soils, and the other
l)lants of the blueberry and heather families almost without excep-
tion occurred likewise on noncalcareous formations.

The Avriter's own experiments in groAving blueberries in limed
soils haA^e not proceeded Avith the same smoothness as some of his
other experiments, but the results, though at first misleading, have
uniformlv been exceedingly instructive, though not ahvaA's in the

^Rhodora, vol. 9, 1907, pp. 149-193.
193

20 EXPERIMENTS IN BLUEBERRY CULTURE.

direction originally contemjjlated, and in the end have been fully
conclusive.

On May 26, 1908, six blueberry seedlings were potted in six 14-
ounce drinking glasses in a good i^eaty blueberry soil, in which,
however, 1 per cent of air-slaked lime ° had been mixed immediately
before the potting was done. Six other plants were similarly potted,
but without the addition of lime. The unlimed plants grew
normally. The younger leaves of the limed j^lants, however, began
to wilt the same day on which they were potted. On June 1 all
the leaves on all six plants were withered, though parts of the stems
were still green and i^lump. Tlie leaves did not turn purplish or
yellowish, as is usual with sickly blueberr}' plants, but either re-
tained their green color after withering or turned brown. No new
root growth took place in any of the limed pots, and by July 10 all
the plants were dead.

Another series of six plants, also potted on May 26, 1908, but m
a sterile soil containing no peat, by accident received a very small
amount of lime. Most of the leaves on these plants withered during
the first few days, but the plants subsequently recovered and made
as good growth as could have been expected from the general char-
acter of their soil.

From these experiments the writer concluded that the blueberry
was exceedingly sensitive to lime and that the slightest admixture
of it in the soil would be immediately fatal to the life or at least
the health of a blueberry plant. This conclusion, however, was
erroneous, as subsequent experience showed. This first experiment
may therefore be dismissed with tlie explanation that in all proba-
bility the immediate collapse of the plants was due to a caustic effect
of the lime used. In none of the later lime experiments did this
immediate collapse occur and in none was the lime so applied that
it came into contact with the blueberry roots while in a caustic
condition.

Still laboring under an erroneous conception of the supersensi-
tiveness of the blueberry plant to minute quantities of lime, the
writer, desiring to produce fresh examples of this phenomenon, in
November, 1908, placed a very small quantity, a few milligrams, of
air-slaked lime on the surface of the soil in each of three 2-inch
pots containing a small blueberry plant. No effect was produced
either at first or for several weeks. On December 19, 1908, a large
surface application of carbonate of lime was made to the same three
plants, a gram to each pot, and the lime was washed down with
water. The expected collapse did not occur. The limed plants con-
tinued to grow as luxuriantly as their unlimed neighbors. The con-

° Computed ou the dry weight of the soil.

193

SLOW PERCOLATION OF LIME THROUGH PEAT. 21

elusion was reached that the reason why the growth of the plants had
not been affected was because the lime had not penetrated sufficiently
into the soil. Another and more drastic experiment was therefore
determined upon.

On March 10, 1909, six blueberry plants in 4-inch pots containing
a good blueberry soil were set apart from their fellows and watered
^Yith ordinary limewater, a saturated solution of calcium oxid, 1.25
grams per liter of water. The af)plications made*were of such an
amoimt that the soil in the pot was thoroughly wetted each time, and
usually a small excess quantity ran through the hole in the bottom
of the pot.

For more than seven months, until October 22, 1909, these pots
received no other water than limewater. During this period the
plants continued to grow in a normal manner, their average height
increasing from 4| to 14 inches. The lime appeared to have no
deterrent etfect whatever on the growth of the plants. A computation
based on the total amount of limewater used showed that each pot
must have received about 18 grams of lime. An analysis of the soil
in one of the pots after the limewater applications had ceased gave
14 grams. This amount was enormous, considered from the stand-
point of agricultural usage. The soil, which had about one-third
the weight of a*i ordinary soil, was over 8 per cent lime. This is the
equivalent of about 25 tons of lime per acre mixed into the upper
6 inches of the soil.

Now, it was already known from the experiment described on page
23 that in this soil when containing as much as 1 per cent of lime
blueberry plants should either die or barel}^ remain alive. As a
matter of fact these limewater plants were making excellent growth.
A careful examination of the contents of one of the pots was then
made. The surface of the soil was covered with a hard gray crust
of lime. Immediately underneath for a depth of about half an inch
the soil was black and contained no live blueberry roots. There was
a zone of the same black rootless soil along the wooden label that
reached from the top to the bottom of the pot. In all other parts
of the dark-brown peaty soil there was a dense mass of healthy
roots, which reached down also into the open spaces among the
broken crocks in the bottom of the pot. The lime appeared to have
penetrated only into the superficial portions of the soil. A chemical
test showed that the black rootless layer was densely impregnated
with liuie, while the brown peaty portion containing the growing
roots still o'ave the acid reaction that was characteristic of the whole
potful of soil before the limewater applications began.

Since all the water that the limeless root-bearing portion of the
soil had received during the preceding seven months had come from
the limewater applications, it was evident that the lime contained

193

22 EXPERIMENTS IN BLUEBERRY CULTURE.

in the limewater had been deposited in the upper laj'ers of the soil.
The following laboratory experiment confirmed this. A small quan-
tity of the acid peaty soil used in growing blueberries was placed
in a o-lass vessel and moistened. Then dilute limewater reddened by
the addition of phenolphthalein, a substance giving a delicate color
test for alkalies such as lime, was stirred into the soil and the mixture
poured into an ordinary paper filter. The water came through the
filter without a trace of red color, showed none after boiling, to drive
off any possible carbonic acid, and when tested with ammonia and
ammonium oxalate showed not a trace of lime. The precipitation
of the lime had been complete and practically instantaneous. Only
ten seconds had elapsed between the time when the limewater was
added to the soil and the time when the liquid entirely free from lime
began to drop through the filter.

In order to ascertain whether a large part of the lime in the lime-
water used on the plants may not have passed through the pots by
running down the partially open channel along the label, some lime-
water was poured upon the surface of one of the pots. The excess
water that soon began to drip through tlie bottom of the pot was
tested for lime. It was found that while the limewater poured into
the pot contained 0.1014 per cent of lime, the water that came
through contained only 0.004(3 per cent. In other w:ords a pot of soil
that for over seven months had been used essentially as a limewater
filter still continued to extract over 95 per cent of the lime contained
in the limewater that was passed through it, notwithstanding the
fact that there was a partially open channel down one side of the
pot. It is believed that had the soil been evenly compacted in the
pot no lime whatever would have been able to pass through, bu.t that
all would have been precipitated in the uppermost layers.

While the experiment has no important bearing on the subject of
blueberry culture it is of very great significance in its bearing on the
method of applying lime to acid soils in ordinary agricultural prac-
tice. A surface application of lime would have no appreciable effect
in neutralizing the acidity of a soil unless the soil was so sandy or
gravelly or otherwise open that the rain water containing the dis-
solved lime could run down through it practically without obstruc-
tion. A surface dressing of lime would have little effect in neutraliz-
ing the acidity of an old meadow or pasture. To secure full action
of the lime, as now generally recognized in the best agricultural
practice, requires its intimate mixing with the soil, such as can be
accomplished by thorough harrowing, especially after joutting the
lime beneath the surface Avith a drill. A full discussion of the phys-
ical reasons for the deposition of the lime in the upper layers of the
soil, when not worked into it mechanically, is given in Bulletin 52 of
the Bureau of Soils, published in 1008.

193

INJURIOUS EFFECT OF LIME.

23

Among the experiments with bhieberry seedlings in different soil
mixtures started on December 22, 1908, was one in which six plants
were set in glass pots in a peaty soil thoroughly intermixed with
1 per cent ofcarbonate of lime. The first difference that showed be-
tween these and unlimed plants in the same soil was the much feebler
root growth of the limed plants. This w^as followed by an evident
tendency toward feebler stem growth. The relative condition of the
two cultures on April 13, 1009. is shown by photographs of represent-
ative plants reproduced as figures T and 8. The later progress of this

Fig. 7. — Bhielien-y seedling in peat mixture Fig. 8. — Blueberry seedling in peat mixture
limed. (One-half natural size.) unlimed. (Oue-half natural size.)

experiment was interrupted, hoAvever, and its average results vitiated
because the roots of some of the limed plants found their way through
the holes in the bottom of the pots and obtained nourishment from
the unlimed material in which the pots were plunged. Such plants
made nearly as good growth as the unlimed plants. On November
27, 1009, there remained only one of the limed plants whose roots
Avere all inside the pot. This plant was feeble and small, its stem
being only 2^ inches high. Its inferiority to the unlimed plants was
almost as conspicuous as that of the garden-soil plants described on
page IT and illustrated in figure 5.

193

24 EXPERIMENTS IN BLUEBERRY CULTURE.

(4) The swamp blueberry does not thrive in a heavy clay soil.

In its natural geographic distribution the blueberry shows an
aversion to clay soils. Its favorite situations are swamps, sandy
lands, or porous, often gravelly loams. When a blueberry plant
grows upon a clay soil it is usually found that its finer feeding roots
rest in a layer of half-rotted vegetable matter overlying the clay.
Often in such situations the dense covering of interwoven rootlets
and dark peatlike soil may be ripped from the surface in a layer
little thicker than a door mat and of much the same texture. The
roots of the blueberry do not penetrate freely into the underlying clay.

In greenhouse cultures the blueberry shows the same aversion to
clay soils. Various series of blueberry seedlings were potted on May
26, 1908, in different soils in ordinary large drinking glasses. For
one set of six plants a stiff clayey soil was used, such as is common
in the neighborhood of Washington, D. C. The soil in the glass was
mulched to the depth of nearly an inch with half-rotted leaves. In
another six glasses were set six similar plants in a peat soil, the sur-
face mulched in the same way as the others.

In other experiments with this clay soil in earthen pots, the growth
of the plants had always been poor. The present experiment was no
exception. But the feature of greatest interest was the behavior of
the roots. Plate I, from photographs taken October 5, 1908, shows
the root systems of typical plants in the two soils. In the clay soil
almost no root development took place, and in the illustration no
roots are visible. The interrupted black lines in the clay are tunnels
made by larvae or other animals. In the moist leaf mulch covering
the clay, however, the plant developed its roots extensively. Some of
the plants, probably because they were set too deeply in the clay
when the potting was done, failed to send their roots up into the
mulch, and such plants were much inferior in their growth to those
that found the rotted leaves. In the other glass is shown the normal
root growth of a blueberry in a soil suited to it.

(5) The swamp blueberry does not thrive in a thoroughly decomposed leaf

mold, such as has a neutral reaction.

It had been found in earlier experiments that certain soils com-
posed in part of imperfectly rotted oak leaves were good for growing
blueberries. On the supposition that the more thoroughl}^ rotted this
material was the better suited it would be for blueberry growing, a
quantity of old leaf mold was secured for an experiment. The mold
was black, mellow, and of fine texture. The mixed oak and maple
leaves from which it was derived had been rotting for about five
years, until all evidences of leaf structure had disappeared. It had
the same appearance as the black vegetable mold that forms in rich
woods where trilliums, spring beauty, and bloodroot delight to grow.

193

Bui. 193, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate I.

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INJUEIOUS EFFECT OF LEAF MOLD. 25

On February 20, 1909, 25 blueberry seedlings were potted in 3-inch
earthenware pots in a mixture consisting of eight parts by bulk of
the leaf mold just described, one part of clean sand, and one part of
clayey loam derived from rotted grass turf. Fifty other plants were
potted in the same manner except that in place of the mold a peat
was used known from earlier experiments to be well suited to blue-
berry growing. The plants were kept in the greenhouse until warm
weather when they were placed outdoors. All were given the same
treatment, a treatment favorable to good growth.

It had been expected that the plants in the leaf mold would show a
vigorous growth, and it was hoped that the mold might prove even
superior to the peat for blueberry soil mixtures. The experiment as
it progressed, however, showed that such was not the case. The leaf
mold proved to be not merely not a good soil for blueberries but an
extremely poor one, as the following particulars will show.

A\Tien the plants were potted they averaged about 2^ inches in
height. On May 29 the peat-soil plants had an average height of 7{
inches, while the leaf -mold plants averaged 4j inches. At this time
the herbage of the leaf -mold plants was decidedly purpled and yel-
lowish, a coloration which they had taken on soon after they were
potted and from which they never fully recovered. At the end of the
season, after the leaves were shed, the peat-soil plants averaged 13;^
inches in height and the leaf-mold plants Tf inches. On November 29,
1909, five average plants from each lot were cut otf at the surface of
the ground and weighed. The weight of the stems from the leaf -mold
plants was less than one-fifth that from the plants in the good blue-
berry soil.

When these plants were removed from their original seed bed to
be transplanted to the 3-inch pots, such of the original soil as clung
to their roots Avas not shaken off. It is believed that the leaf-mold
plants fed in part on this original soil in making their new growth,
and that without it they would have shown still less increase in
height than they did. The peat-soil plants, moreover, were badly in
need of repotting, even in early summer, and had they been placed in
larger pots the difference in the growth of the plants in the two soils
w^ould have been much greater than it was.

That the influence of the leaf mold was directly deleterious and
that the poor growth of the blueberry plants in it was not due to the
lack of some element that might have been furnished b}^ the addition
of a small amount of the good blueberry soil is show^n by certain inter-
mediate experiments. Along with the cultures described above were
carried two others in which the soil mixtures contained both peat and
leaf mold. In the first, in which the proportion was peat 5, mold 3,
sand 1, and loam 1, the average height of the plants on May 29

193

26 EXPERIMENTS IX BLUEBEEEY CULTUEE.

was 6 inches, and at the end of the season 12^ inches. In the second
lot, in which the proportion was peat 3. mold 5. sand 1, and loam 1,
the average height on ]May 29 was 44 inches, and at the end of the
season llf inches. It will be observed that these two lots of plants
are intermediate in their growth between the first two and that in all
four lots the povert}" of growth is roughly proportional to the amount
of leaf mold used in the soil.

That the weak growth of the plants in leaf mold was not caused by
a compacting of the soil and a lack of aeration, due to too small a
proportion of sand in the mixture, is shown by still another lot of 25
plants which were potted in a soil mixture having the proportion of
mold 6, sand 3. and loam 1. These plants averaged only 4 inches in
height on May 29 and 6^ inches at the end of the season. They grew
even less, therefore, than the plants with only 1 part of sand and 8
parts of mold.

In Plate II. from a photograph made in the winter of 1909-10. is
shown a flat divided into three parts and set on February 10, 1909,
with blueberr}' seedlings of uniform size. The soil in the middle
compartment is a mixture of leaf mold 8 parts, sand 1 part, and loam
1 part. In the compartment to the left the soil is in the proportion
of kalmia peat 8. sand 1. and loam 1: and in the right-hand com-
partment, kalmia peat 4. leaf mold 4, sand 1. and loam 1. It will be
observed that the greater the amount of leaf mold the poorer the
growth of the blueberry plants.

The reason for the unexpected deleterious effect of leaf mold, as
shown by these experiments, is given on page 29 and further discussed
on page 35.

(6) The swamp blueberry does ^*0T thrive in soils having a neutral or

ALKALINE REACTION, JiVT FOE VIGOROUS GROWTH IT REQUIRES AN ACID SOIL.

The consideration of this statement requires first an understanding
of the means used to determine whether a soil is acid or alkaline.
The simplest means is the litmus test.

While one may become sufficiently expert in the use of the litmus
test to form a fair judgment of the degree of alkalinity or acidity in
a soil, an exact determination requires some different method. It
was found that for the weak acids prevalent in the peat soils to the
examination of which the present experiments led. the phenol-
phthalein test was the most satisfactory. If a few drops of phe-
nolphthalein indicator be added to a solution, the solution, if
alkaline, turns instantly pink, and if acid or neutral its color does
not change. The application of this phenomenon to the determina-
tion of the degree of acidity of an acid solution is as follows: A
definite amount of the solution, usually 100 cubic centimeters, is
placed in a beaker, a few drops of an alcoholic solution of phenol-

193

Bui. 1 93, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate II.

CD

r
c
rn

CD

in
3)

<

CO

m
m
o

r_
^

o
en

X
m
>

>

z

D

m
>

o

r
o

METHOD OF TESTING SOIL ACIDITY. 27

phthalein are added, and into this is stirred drop by drop from a
graduated glass tube provided with a stopcock, known as a burette,
a measured amount of some alkaline solution of known strength,
commonly a one-twentieth normal solution, as it is known to chem-
ists, of sodium hydrate. When a sufficient amount of the sodium-
hydrate solution has been dropped into the beaker, the acidity of the
acid solution becomes neutralized and it turns pink. A reading is
made on the burette showing the exact amount of the sodium-hydrate
solution used in elfecting the neutralization. From this reading is
computed the degree of acidity expressed in fractions of a normal
acid solution. Now 100 c. c. of a normal acid solution would require
for its neutralization 100 c. c. of a normal solution of sodium hydrate,
or 2,000 c. c. of a one-twentieth or 0.05 normal solution. In a test of
one of the acid nutrient solutions used in the blueberry cultures,
18 c. c. of a 0.05 normal solution was required to neutralize the acidity
of 100 c. c. of the acid solution. Since 18 c. c. of a 0.05 normal
solution is the equivalent of one-twentieth that amount, or 0.9 c. c. of
a normal solution, the degree of acidity of this acid solution is 0.009
normal. It requires an equal amount of a 0.009 normal alkaline
solution to neutralize it.

In applying this phenolphthalein test to soils the same scale is
used. A soil is regarded as having normal acidity when the acid ex-
isting in a gram of the soil if dissolved in 1 c. c, of water gives a nor-
mal acid solution. If a soil were described as having an acidity of
0.02 normal, it would mean that the extract of 100 grams of it in 100
c. c. of water would be a 0.02 normal acid solution ; that is, that 100
c. c. of the solution would contain 2 c. c. of a normal acid solution.

The method of extraction followed for all the soil acidity tests
given in this paper is as follows : The soil is first air dried at an ordi-
narj'^ room temperature. Ten grams are then weighed out, shaken thor-
oughly with 200 c. c. of hot water, and allowed to stand over night.
In the morning 100 c. c. is filtered otf and boiled to drive away any
carbon dioxid present. The solution is then titrated with a 0.05 nor-
mal solution of sodium hydrate, using phenolphthalein as an indi-
cator. All the tests were made by Mr. J. F. Breazeale. of the Bureau
of Chemistry, to whom the writer is greatly indebted for many cour-
tesies and suggestions on the chemical side of the experiments.

The expression " normal solution " used in this paper, it must be
understood, is the normal solution of chemists, not of surgeons.
Surgeons use the expression " normal salt solution " to describe a cer-
tain weak solution of common salt in water which has the same
osmotic pressure as the blood. A normal solution in chemistry is a
solution of certain fixed strength, or concentration, based on the
molecular Aveight of the substance under consideration. Normal solu-

193

28 EXPERIMENTS IN BLUEBERRY CULTURE.

tions of the various acids have the same degree of acidity. Normal
sohitions of alkaline substances are equal to each other in alkalinity.
A measured amount of a normal solution of an acid will exactly
neutralize an equal amount of a normal solution of an alkaline sub-
stance.

In considering the degree of acidity from the standpoint of the
sense of taste it is convenient to remember that the juice of an ordi-
nary lemon is very nearly a normal solution of citric acid. The juice
of the lemon contains usually from 6 to 7 per cent of citric acid. A
normal solution of citric acid is 6.4 per cent. When the juice of a
lemon is diluted to about ten times its original bulk, as in a large
drinking glass, one has approximately a 0.1 normal acid solution.
When diluted to 100 times, making about a 0.01 normal solution,
there remains only a faint taste of acidity. The acidity of water
after standing long in contact with peat in a barrel sometimes reached
0.005 normal. Bog water, or peat water, is sometimes appreciably
acid to the taste.

Returning now to a consideration of the statement that the swamp
blueberry does not thrive in a neutral or alkaline soil an experiment
in this direction may first be cited. The experiment was made with
twelve small glass pots, each containing a blueberry seedling. The
soil in the pots was a clean river sand. The plants had been in these
pots for eight weeks, watered with tap water. The amount of
nourishment they had received during this time was therefore very
small, especially since, when transplanted into the pots, all the soil
of the original seed bed had been carefully removed from the roots.
Nevertheless during these eight weeks all the plants had made exten-
sive, even luxuriant, root growth. The tops, however, had made no
growth. There had been complete stagnation or withering of the
youngest leaf rudiments, and the mature leaves became and remained
deeply purpled.

Beginning on February 17, 1909, eight weeks after the plants had
been potted in the sand, as already stated, five of the pots were wa-
tered with an acid nutrient solution made up, in accordance Avith the
advice of Mr. Karl F. Kellerman, of the Bureau of Plant Industry, as
follows :

Potassium nitrate (KNO3) 1. gram.

Magnesium sulphate (MgS04) 0.4 gram.

Calcium sulphate (CaS04) 0. 5 gram.

Calcium monophosphate (CaH4P20s) 0.5 gram.

Sodium chlorid (NaCl) 0. 5 gram.

Ferric chlorid (FeCU) Trace.

Water 1' <500 c. c.

This solution gave an acidity test of 0.012 normal.

193

INJURIOUS EFFECT OF ALKALINE SOILS. 29

Five other plants from the same twelve were watered with an alka-
line nutritive solution of the following composition :

-Potassium nitrate (KNO3) 1. gram.

Magnesium sulphate (MgSOi) 0.4 gram.

Calcium sulphate (CaS04) 0. 5 gram.

Potassium diphosphate (KH2PO4) 0. 4 gram.

Sodium chlorid (NaCl) 0. 5 gram.

Ferric chlorid (FeCla) Trace.

Water 1, 000 c. c.

By the addition of a sufficient quantity of sodium hydrate the re-
action of this solution was made alkaline to the degree of 0.006
normal.

Two of the twelve plants were left as checks, being still watered
with tap water.

On March 25, thirty-six days after the watering began, the five
plants fed with the acid nutritive solution were restored to a nearly
normal green color, and all had begun to put out healthy new growth.
The two check plants watered with tap water were still red-purple
and stagnant. Of the five plants watered with the alkaline nutrient
solution, three were stagnant and somewhat purplish, one was dying,
and one was dead.

Figures 9 and 10, from photographs taken on April 15, 1009,
show a typical stagnant plant that had been watered with the alka-
line solution, and a typical plant watered with the acid solution which
had begun to make new growth from the summit of the old stem and
was pushing out a vigorous new shoot from the base. The experi-
ment was terminated not long afterwards, but there was every pros-
pect that had it been continued the acid-fed plants would soon have
made growth comparable with that shown in figure 8 (p. 23).

Looking toward the aciditv or alkalinitv of the other cultures thus
far cited, it may be stated that the rich garden soil described on
page 14, which was so remarkably deleterious to blueberry seedlings,
was alkaline. The rose cuttings and the alfalfa, which grew so well
in that mixture, much prefer a somewhat alkaline soil. Indeed,
alfalfa can not be grown with any degree of success in any soil
except one with an alkaline reaction. AAlien grown in the humid
eastern United States alfalfa is rarely successful, except on calcareous
soils, unless the natural acidity of the soil has been neutralized by
suitable applications of lime.

The limed soil, deleterious to blueberry plants, described on page
23, gave a neutral reaction with phenolphthalein.

The heavy clay soil described on page 24, in which blueberry plants
made very little growth, Avas neutral.

The thoroughly decomposed leaf mold described on pages 24 to 2G,
which was shown by experiment to be markedly deleterious to the

193

30

EXPERIMENTS IN BLUEBERRY CULTURE.

blneberr}^, was distinctly alkaline. A chemical analysis of this mold
showed that it contained 2.86 per cent of calcium oxid.

The good blueberry soils in all the experiments were acid, the acidity
at times of active growth varying from 0.025 normal down to 0.005
normal.

It is of interest and suggestive of utility in indicating the acid or
nonacicl character of soils to record that in the case of the alkaline
leaf mold described on page 24 the surface of the soil in all the pots
became covered in a few months with a growth of a small moss iden-

tified through the courtesy of Mrs. N. L.

Britton as Physcomitrium
iminersum. On the sur-
face of acid kalmia-peat
soils the characteristic
green growth consisted of
microscopic alga^, accom-
l^anied often by fern pro-
thallia and other mosses,
but never Physcomi-
trium.

The natural distribu-
tion of blueberries and
their relatives indicates
their close adherence to
acid soils. They occur in
abundance throughout the
sandy Coastal Plain of the
Atlantic seaboard. They
occur generally through
the cool humid hill lands
of New England. They
occur in sandy pine bar-
rens and peat bogs
throughout the eastern
United States. They are absent, on the contrary, from limestone
soils, rich bottom lands, and rich woods, where the soils are neutral
or alkaline. In the lower elevations of the whole subarid West, where
acid soils are almost unknown, these plants do not occur. Within
reach of the fogs and heavv rainfall of the Pacific coast or on the
higher mountains of the interior, where conditions favor the devel-
opment of acid soils, blueberries occur again m characteristic abun-
dance.

From an examination of the reports of those who have attempted
at the agricultural experiment stations to domesticate and improve
the blueberry, it is evident in the light of the present experiments
that the primary reason for these failures was that they did not recog-

193

Fig. 9. — Blueberry seedlins fed with alkaline nutrient
solution. (Natural size. )

BENEFICIAL EFFECT OF PEAT.

31

nize soil acidity as a fundamental requirement of these plants. It
was perhaps natural to give the blueberry the same garden culture
that when applied to other bush fruits has resulted in their distinct
improvement. But the ordinary garden operations tend to make even
an acid soil neutral or alkaline, and in such a soil the blueberry does
not thrive.

The death and decay of blueberry roots, with which the injurious
effect of alkaline soils is associated, are discussed on pages 64 and 05.

(7) The favorite type of acid soil for the swamp blueberry is peat.

Although the swamp blueberrj^ sometimes grows on upland soils
its typical habitat, as its name implies, is in swamps or bogs. The
cranberry, it is well
known, is cultivated al-
most exclusively in bogs.
In clearing bog land pre-
paratory to the planting
of cranberries one of the
necessary precautions is to
remove all roots of the
SAvaniiD blueberry. If the
roots are allowed to re-
nuiin in the ground, they
send u]) vigorous shoots,
and these, unless pulled,
develop into robust plants
which occupy the ground
to the great injury of
the cranberries. Large,
healthy, and productive
bushes of the swamp blue-
berry are frequent, almost
characteristic, inhabitants
of the uncultivated bor-
ders of cranberrv boo:s.

Peat bogs, in the con-
ception of geologists, are
incipient coal beds. The
transformation of peat
into coal occupies very
long periods, perhaps some
uiillions of years. Peat is made np chiefly of vegetable matter,
the dead leaves, stems, and roots, of bog plants which are only
partly decayed. Their full decay is prevented primarily by
the presence of w^ater, which keeps away the air. The bacteria,

193

Fig. 10. — Blueberry seedling fed with acid nutrient
solution. ( Natural size. I

32 EXPERIMENTS IN BLUEBERRY CULTURE.

fungi, and other organisms by which ordinary decomposition pro-
gresses can not live under this condition and decay is suspended.
The acids developed by this vegetable matter in the early stages of
its decomposition are also destructive to some of the organisms of
deca}^, especially bacteria. These acids act therefore as preserva-
tives and greatly assist in preventing decomposition. So effective
are these conditions of acidity and lack of oxygen, assisted in north-
ern latitudes by low temperature, which is also inimical to the organ-
isms of decay, that bogs sometimes preserve for thousands of years
the most delicate structures of ferns and mosses.

Tests have been made of the acidity of typical peat bogs in New
England where swamp blueberries are growing. These peats were
always found to be acid and the degree of acidity was within the
range found satisfactory for blueberr}^ plants in pot cultures.

The reason why peat is a particularly satisfactory type of acid soil
for blueberries is, apjjarentW , because the acidity of peat is of a mild
type, yet continually maintained.

Not all peats are acid. About the larger alkaline (but not destruc-
tiveh^ alkaline) springs of our southwestern desert region are
deep deposits of rather well-decayed vegetable matter that must
be classed as peat. The characteristic vegetation growing on these
peats is tule {Scirpns occidentalis and S. olneyi). The water of
one of the great tule swamps of the West (Lower Klamath Lake in
southern Oregon), which contains thick beds of peat formed chiefly
from Scirpus occidentalis, has been examined recently by Mr. J. F.
Breazeale, at the request of Mr. C. S. Scofield. It was found to con-
tain sodium carbonate, and the peat gave a distinctly alkaline reaction.

The peat formed about marl ponds in the eastern United States
is also, in all probability, alkaline unless formed at a sufficient dis-
tance from the lime-laden water to be beyond the reach of its acid-
neutralizing influence.

Such alkaline peat-s, while not actually tried, are believed from
other experiments to be quite useless for groAving blueberries. Cer-
tain it is that neither blueberries nor any of their immediate relatives
are found on these soils in a wild state. In the eastern United
States, however, such alkaline peats are comparatively rare, and the
use of the word " peat " conveys ordinarily the idea of acidity. All
the soils used by gardeners under the name of peat are acid.

(8) Peat suitable for thf swamp blueberry may be found either in bocs or
ON the surface of the ground in sandy oak or pine woods.

In the vicinity of Washington deposits of bog peat are few and of
limited extent, and the peat is thin. As a matter of fact no bog peat
of local origin is used by the gardeners and florists of AA^ashington.
For growing orchids, ferns, azaleas, and other peat-loving plants,
either peat shipped from New Jersey is used or a local product some-

193

FORMATION OF KALMIA PEAT. 33

times known as " Maryland peat." This material is not a bog peat at
all, and since it is of very great interest in connection with these blue-
berry experiments, for it was the principal ingredient in a majority
of the successful soil mixtures used, it is desirable that the reader
have a comprehensive idea of its character.

Maryland peat, as brought to the greenhouses of the United States
Department of Agriculture, consists of dark-brown turfs or mats, 2 to
4 inches thick, made up of partially decomposed leaves interlaced with
fine roots. It is found in thickets of the American laurel {Kalmia
latifol'id) where the leaves of this shrub, usually mixed with those of
various species of oak, have lodged year after year and the ac-
cumulated layers have become partly decayed.

The nature of the deposit may be easily comprehended by means
of the accompanying illustrations. The photographs from which the
illustrations were made were secured through the courtesy and skill
of Mr. G. N. Collins, of the Bureau of Plant Industry. The photo-
graphs were made in the month of April, 1908, in a laurel thicket at
Lanham, Md. After one photograph was made, the layer of leaves
represented by it was removed and another photograph was taken
showing the layer immediately underneath.

In Plate III, figure 1, is shown the top layer of the leaf deposit aS
it appeared in April, 1908, consisting of oak leaves of various species
which fell to the ground in the autumn of 1907. The next under-
lying layer is shown in Plate III, figure 2. The laurel leaves here
shown are those that fell in the summer of 1907. Laurel being an
evergreen, its leaves are not shed in the autumn like those of the oaks.
They remain on the bush until the new leaves of the following spring
are fully developed and then the old leaves begin to fall. It is this
circumstance of the fall of the oak and laurel leaves at different
periods of the year that enables one to recognize the different layers
and know their exact age. The third layer, shown in Plate IV, figure
1, consists of oak leaves of the autumn of 1906. This layer was moist
and decomposition was well started. The presence of fungous growth
is evident, as is also the excrement of various small animals. Myria-
pods, or thousand-legged worms, and the larvfe of insects must play a
very important part under some conditions in hastening the de-
composition of leaves. The fourth layer, Plate IV, figure 2, consist-
ing of laurel leaves shed in the summer of 1906, is in about the same
condition as the preceding layer. In the fifth layer, Plate V, figure 1,
are shown the leaves of 1905, but the layer of oak leaves is not readily
separable from the laurel. The rotted leaves crumble readily and
decomposition has so far progressed that a few oak rootlets are found
spread out betAveen the flattened leaves. Plate V, figure 2, shows the
rotted leaf layers of 1904 interlaced with the rootlets of laurel and oak.
It is this root-bearing layer, 2 inches or more in thickness, of which
54708°— Bull. 193—10 3

34 EXPERIMENTS IN BLUEBERRY CULTURE.

Maryland peat is composed. The lower portions of it reach a some-
what greater degree of decomposition than is here shown.

In a rich woods of the trillium-producing type, such as a fertile
sugar-maple forest, one may observe that the leaves in rotting sel-
dom retain their form longer than two years and that the line of de-
marcation between the thin leaf litter of the forest and the underlying
w^oods mold is sharp and clear.

In the sugar-maple woods the decomposition of the leaves is rapid.
In the Maryland or kalmia peat, as it ma}" be called with more exact-
ness, the decomposition is slow. The cause of this difference in the
rate of decomposition is the difference of acidity in the two cases, and
this in turn is dependent on the nature of the leaves and of the under-
lying soil, particularly whether the soil is acid or alkaline. A slight
alkalinity in a soil greatly favors the decomposition of the leaves
overlying it. An acidity as strong as that shown to occur in newly
fallen oak leaves (see p. 62) can not help having a pronounced effect
in maintaining the aciditv of the lower leaf lavers; for it must be
remembered that these acids are soluble in rain water, and are there-
fore continually leaching down from the upper through the lower
layers of rotting leaves.

These upland leaf deposits, in which decomposition is retarded for
many years, the writer regards as essentiall}^ peat, and to distinguish
them from bog peats he would call them upland peats. An upland
peat may be described as a nonpaludose deposit of organic matter,
chiefly leaves, in a condition of suspended and imperfect decompo-
sition and still showing its original leaf structure, the suspension of
decomposition being due to the development and maintenance of an
acid condition which is inimical to the growth of the micro-organisms
of decay.

The use of the name '' leaf mold," sometimes applied to this upland
peat, should be restricted to the advanced stages in the decomposition
of leaves, in which leaf structure has disappeared. True leaf mold,
furthermore, is neutral or alkaline, so far as tested.

When kalmia peat is to be used for growing blueberries it should
be piled and rotted for several months. An experience which empha-
sizes the need of this treatment is given on page 60. If stacked
as soon as it is dug it usually retains sufficient moisture to carry the
rotting forward, even if the stack is under cover.

Kalmia peat has proved to be a highly successful soil for grownng
blueberries. It has been tried both pure and in many mixtures, as
will be described in the paragraphs beginning on page 51.

An upland peat formed of the leaves of scrub pine {Pinus virgin-
iana)has also been tried for blueberry seedlings. They grow well in it.

Oak leaves, it is believed, rotted for one or two years would make a
good blueberry soil. In the Arlington National Cemetery is a ravine

193

Bui. 193, Bureau of Plant Industry, U. S. Dept. of Agriculture

Plate III.

Fig. 1.— Formation of Kalmia Peat, Top Layer.
Oak leaves of the preceding autumn. (Natural size.)

Fig. 2.— Formation of Kalmia Peat, Second Layer.
Kiilinia leaves of the preceding summer. (Natural size.)

Bui, 193, Bureau of Plant Industry, U. S, Dept. of Agriculture.

Plate IV,

Fig. 1.— Formation of Kalmia Peat, Third Layer.
Oak leaves 2 years old. (Nattiral size.)

Fig. 2.— Formation of Kalmia Peat, Fourth Layer.

Kalmia leaves '2 years old. (Natural size.)

Bui. 193, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Plate V.

Fig. 1.— Formation of Kalmia Peat, Fifth Layer.
Mixed oak and kalmia leaves 3 years old. A few live rootlets of oak are shown. (Natural size.)

Fig. 2. -Formation of Kalmia Peat, Sixth Layer.

Mixed oak and kalmia leaves 4 years or more old interlaced with live rootlets of oak and kalmia

(Natural size.)

ACIDITY OF BOGS AND SANDY UPLANDS. 35

in whicli large quantities of leaves, chiefl}- oak, have been clumped
for many years. Samples taken there in late November, 1909, show
an acidity in the case of freshly fallen leaves of 0.4 normal; in leaves
apparently 1 year old, 0.006 ; and in leaves about 2 years old, 0.002.

A condition of great interest was found in one of these piles of
leaf mold which was several years old. It was mellow and black, and
the evidence of leaf structure had disappeared. When submitted to
the phenolphthalein test it proved to be alkaline, and upon chemical
examination it was found to contain 3.55 per cent of lime (CaO).
In this case decomposition had progressed so far, it is suggested, that
the lime in the leaves, remaining constant in amount and probably
having been changed to a more soluble state, had neutralized the
remaining acidity. The material, then becoming alkaline, had pro-
ceeded to decompose with greater rapidity, until a real mold had been
formed.

The condition here observed is doubtless the same as that which
occurs in the drained bog, or so-called " muck," lands of Michigan.
When first plowed they will grow only certain acid-resistant crops,
such as buckwheat or potatoes, but later, as their acidity disappears,
they come to attain a very high degree of fertility. It is probably a
phenomenon of similar character Avhich is taking place in the drained
swamp lands of the lower Sacramento River in California, where the
soil, which is already in a state of remarkable fertility, is becoming
increasingly alkaline.

Here allusion may be made to another phenomenon, that of the
occurrence of the swamp blueberry and certain other plants, such
as the purple lady's-slipper {Cypripedivm acaide) and the swamp
honeysuckle {Azalea nndifora)^ in two kinds of situations — one a
peat bog, the other a sandy, well-drained, and often dry upland. The
favorite explanation of this phenomenon among botanists is that these
plants are naturally adapted to the drier situation and that in the bog
they find a situation of " physiological dryness," or vice versa.
While the existence of physiological dryness in peat bogs is not
questioned, the explanation that a bog plant finds an upland situation
congenial because it is dry certainly will not answer for the blue-
berry. Its occurrence in these two habitats is dependent on the
acidity of both situations. These experiments have shown that no
amount of dryness will make a blueberry flourish in an upland soil
if that soil is not acid.

(9) Fob active growth the swamp blueberry requires a well-aerated soil.
Conversely, the swamp blueberry does not continue in active growth
IN a soil saturated with water.

In its natural distribution the swamp blueberry does not grow in
the lower, wetter tyj^e of bog. In a typical leatherleaf {Chamae-
daphne calycidata) bog, for example, the swamp blueberry is found

193

36 EXPERIMENTS IX BLUEBERRY CULTURE.

either about the margin of the bog or on hummocks. In both these
situations most of the roots of the bhieberry bushes stand above the
summer level of the water. ^Vlien a bog has l)een built up bv the
growth of vegetation and the accumulation of the debris until the
surface is above the summer water level, the swamp blueberry' will
occur ofenerallv over the bog.

An examination of blueberry plants occurring on hummocks and
bog margins has shown that such roots as extend beneath the per-
manent summer water level bear few feeding rootlets or none at all.

In one experiment it was attempted to grow blueberry seedlings
in water cultures containing various dissolved nutrients. It was
found that the roots made no new gi'owth. that the new leaves were
few and small, and that the general health of the plants was not
good, whatever the character of the nutrient substances in the solu-
tions. It was frequently observed also in the various soil cultures,
particularly those in undrained glass pots, that the continued satu-
ration of the soil with water reduced the root growth and enfeebled
the Avhole plant. Continued excessive watering of potted blueberry
plants Avas always found injurious.

The observations just recorded must not be understood to mean
that submergence of the roots is always injurious to the swamp blue-
berry. In winter and early spring the water level of bogs containing
blueberries often remains high enough for several months to com-
IDletely submerge the Avhole root system of the plants. On the lower
end of the AVankinco cranberry bog near Wareham, Mass., are some
native bushes of the swamp blueberry, the roots of which have been
submerged in 3 feet of water from December to ^lay each year for
about twenty years. These bushes when observed in September. 1909,
gave every evidence of vigor. Their twig growth was of gcK)d length
and thickness, their foliage was dense and of a healthy color, their
flowering buds for the next vear were fairlv numerous, and the bushes
were said to be as productive of fruit as neighboring bushes on higher
ground.

It would appear from these facts that, while submergence during
the dormant period is not injurious to the swamp blueberry, its roots
during their actively growing period must be kept above the water
level so as to be well aerated.

(10) .^XRATION CONDITIONS S.\TISFACTORY FOB THE SWAMP BLUEBKRBY ARE PREVA-
LENT IN SANDY SOILS.

The experiment cited above on this page showed that blueberry
seedlings having their roots suspended in nutrient solutions failed to
make a normal growth even though the solutions were suitably acidu-
lated. This failure was ascribed to lack of aeration. In another
experiment, described on pages 28 and 29, it was shown that a similar
nutrient solution when used to water a blueberry plant potted in sand
produced a normal growth of both roots and stems. The sand fur-

AERATION CONDITIONS IN SAND AND PEAT. 37

nished no appreciable nourislinient and the only essential difference
in the two cases was the abundant root aeration afforded by the sand
culture. Sand is therefore regarded as having been shown experi-
mentally to furnish conditions suitable for soil aeration.

In all the experiments in which blueberry seedlings were grown in
sard cultures suitably acidulated, the root growth was good, even
when very little nourishment was given the plant, and when fed with
a weakly acid nutrient solution or with peat water the sand-potted
plants always made a luxuriant root growtii.

In their wild state blueberries are especially prevalent on the sandy
soils of the Atlantic Coastal I*lain, as well as on sandy plains and i)ine
barrens in the inlci'ior. The drainage of such soils is good and their
aeration is excellent.

(11) Aeration conditions satisfactokv kou tuk swamp 1!luebekky akk found
in drained emjkous peat.

Kalmia peat when in the original turfs or mats is full of small
roots of oak, kalmia, and other plants. In that condition it is remark-
ably porous and w^ell aerated. Pieces of these turfs were used with
great success in the bottoms of pots, in place of crocks, to afford drain-
age. For a potting soil, however, kalmia peat can not easily be used
until the soil has been shaken from the mass of roots or has been
rulibed through a screen. Even in that condition the fragments of
leaves and rootlets make the whole mass porous. A ])()t containing
pure kalmia peat prepared by such rubbing often remains moist, yet
well aerated, for days at a time wnthout watering. This moisture con-
dition is due to two remarkable properties of peat, its ability to hold a
large amount of water, and the tenacity with which it clings to it.

Kalmia peat taken from the interior of a stack after it has remained
several months under cover ordinarily contains 100 ])er cent of
water, comj)uted on the dry weight of the peat. Even with this very
high water content a i:)eat soil is in a beautiful condition of tilth,
mellow, well aerated, and to the sight and touch apparently only
moderately moist. Ordinary loam in a similar condition contains
only about 18 per cent of water, and sand about .'^ per cent. When
saturated with water the moistui'e content of kalmia peat is about
500 i)er cent of its dry weight.

The ability of peat to retain its moisture depends in part on the
gi-adual drying of the superlicial layers and the consequent formation
of a nudch, but more i)articularly is it dependent on a certain phys-
ical affinity that peat possesses for water. The comparative strength
of this water-holding power in different soils may be tested by sub-
jecting them to a powerful centrifugal force, which tends to throw
the moisture out of the soil. The standard centrifugal force used
is a thousand times the force of gravity. The percentage of moisture

193

38 EXPEETMENTS IN BLUEBERRY CULTURE,

remaining in the soil after this treatment is known as the moisture
equivalent of that soil. A test of kalmia peat made by Dr. Lyman
J. Briggs, of the Bureau of Plant Industry, the originator of this
method of measurement, showed a moisture equivalent of 142 per
cent, as compared with about 30 per cent for clay, 18 per cent for
loam, and 2 to 4 per cent for sand.

From Avhat has been said it is evident that fibrous kalmia peat
has physical characteristics that allow the soil to be amply aerated,
while at the same time holding abundant moisture for the supporting
of plant growth.

In this connection reference may be made to the influence of earth-
worms on potted blueberry plants. Late in the winter of 1908-9
it was noted that among the blueberry seedlings of 190T, which had
been brought into the greenhouse, were several in which the growth
was feeble, although others of the same lot were growing vigorously.
It was noted also that the soil in the pots in which the feeble plants
were growing contained earthworms, as evidenced by the excre-
ment or casts deposited b}^ them on the surface. The worms
themselves were easily found by knocking the earth ball out of the
pot, and the soil was seen to have been thoroughly worked over by
the worms.

It was supposed at first that the soil (a mixture of peat 8, sand 1,
loam 1) in the process of digestion to which it had been subjected
in passing through the alimentary canal of the earthworms might
have become alkaline and for this reason injurious to the blueberry
plants. When tested with phenolphthalein, however, the soil in the
pots containing earthworms and feeble plants was found to be of the
same acidity as that in the pots containing no earthworms and with
vigorously growing plants. Furthermore the fresh casts themselves
were of a similar degree of acidity.

The texture of the soil, however, in the pots containing worms was
very different from that in the others. It was plastic, very fine
grained, almost clayey, the organic portion having been very finely
ground evidently in passing through the gizzard and other digestive
a