Weevil-resisting adaptations of the cotton plant

hi DEPARTMENT | OF. AGRICULTURE.
«= BUREAU OF PLANT INDUSTRY BULLETIN NO. 88.

S . yee O ie B a GALLOWAY, Chief of Bureau,
h Ww *) ae Pe ee s

WEEVIL: -RESISTING ADAPTATIONS —
OF THE COTTON PLANT.

= ; ee FE COOK,
Broxomst IN seven: OF INVESTIGATIONS IN THE AGRICULTURAL
_ Economy « OF TROPICAL AND SUBTROPICAL PLANTS.

ss) 8 Tggump Tanvary 13, 1906-

\

aue. 2 os
f teeth

EP ORAL) 8
Book __’ Cs & B

7 5

aN
+ he
,

ete

"NOLLOD DONILSISSY-MNASAM HLIM SLNAWIYAdXy 40 SN30S SHL ‘VIVWALVNY 'ZVd VESA VLIV ‘WINONVOAS LV AATIVA

PLATE I.

of Agriculture.

Bul, 88, Bureau of Plant Industry, U. S. Dept.

U.S. DEPARTMENT OF AGRICULTURE.
BUREAU OF PLANT INDUSTRY—BULLETIN NO. 88.

B. T. GALLOWAY, Chief of Bureau.

WEEVIL-RESISTING ADAPTATIONS
OF THE COTTON PLANT.

BY

O,- FS COOK,
BIONOMIST IN CHARGE OF INVESTIGATIONS IN THE AGRICULTURAL
Economy OF TROPICAL AND SUBTROPICAL PLANTS.

IssurpD JANUARY 13, 1906.

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
POG:

ey \
es

BUREAU OF PLANT INDUSTRY.

B. T. GALLOWAY,
Pathologist and Physiologist, and Chief of Bureau.

VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS.
ALBERT F. Woops, Pathologist and Physiologist in Charge, Acting Chief of Bureau in Absence of Chief.
BOTANICAL INVESTIGATIONS.

FREDERICK V. COVILLE, Botanist in Charge.

FARM MANAGEMENT.

WS ip SPILLMAN, Agriculturist in Charge.

POMOLOGICAL INVESTIGATIONS.

G. B. BRAcKETT, Pomologist in Charge.

SEED AND PLANT INTRODUCTION AND DISTRIBUTION.

A. J. PretErs, Botanist in Charge.

ARLINGTON EXPERIMENTAL FARM.

L. C. CorBETT, Horticulturist in Charge.

INVESTIGATIONS IN THE AGRICULTURAL ECONOMY OF TROPICAL AND SUBTROPICAL
PLANTS. .

O. F. Cook, Bionomist in Charge.
DRUG AND POISONOUS PLANT INVESTIGATIONS, AND TEA CULTURE INVESTIGATIONS.
RopneyY H. TRUE, Physiologist in Charge.
DRY LAND AGRICULTURE AND WESTERN AGRICULTURAL EXTENSION.
CARL 8. SCOFIELD, Agriculturist in Charge.
EXPERIMENTAL GARDENS AND GROUNDS. -
E. M. BYRNEs, Superintendent.
SEED LABORATORY.

EpGAr Brown, Botanist in Charge.

J. E. ROCKWELL, Editor.

JAMES E. JONES, Chief Clerk.

INVESTIGATIONS IN THE AGRICULTURAL ECONOMY OF TROPICAL AND SUBTROPICAL
PLANTS.

SCIENTIFIC STAFF.
j AN 8 1907 O. F. CooK, Bionomist in Charge.
10 . G. N. CoLuins, Assistant Botanist.
F. L. LEwTon, Scientific Assistant.

H. PITTIER, Special Agent.

LETTER OF TRANSMITTAL.

U. S. DeprartMEentT or AGRICULTURE,
Bureau or Puiant Inpustry,
OFFICE OF THE CHIEF,
; Washington, D. C., September 26, 1905.

Sir: I have the honor to transmit herewith a report on “ Weevil-
Resisting Adaptations of the Cotton Plant,” and to recommend it
for publication as Bulletin No. 88 of this Bureau. This report has
been prepared by Mr. O. F. Cook, bionomist in charge of investiga-
tions in the agricultural economy of tropical and subtropical plants.
It contains an account of his observations and experiments which
show that some of the varieties of the cotton plant have definite
weevil-resisting characters. The establishment of these facts opens
new and unexpected lines of approach to cultural solutions of the
weevil problem. -

The investigation of cotton referred to in this report was begun
in March, 1904, through the Laboratory of Plant Breeding, there
having been set aside for it from the emergency cotton boll weevil
appropriation a part of the funds which had been devoted to the
breeding of weevil-resistant cotton. The existence of a field culture
of cotton in the presence of the boll weevil had been ascertained by
Mr. Cook during a visit to Guatemala in 1902, and it was hoped that
the immunity of the cotton might prove to be due to some weevil-
resistant quality.

The first result of detailed observations was the discovery of the
weevil-eating kelep or so-called Guatemalan ant, which has been
made the subject of previous reports through the Bureau of Ento-
mology. It now appears that the usefulness of this insect is not
limited to the boll weevils which it catches and kills. By making a
regular field culture of cotton possible in the presence of the boll
weevil it has contributed in an important manner to the development
of the weevil-resisting characters here described. The cotton plant,
it seems, has been greatly modified in protecting itself against the
ravages of its insect enemy. Not only has it attracted the kelep to
its service and developed other means of defense which are more

3

4 LETTER OF TRANSMITTAL.

direct, but even the lint, on the peculiar character of which the com-
mercial value of the crop depends, appears to find its chief use to the
plant in excluding the weevil larvee from the seed. Our Sea Island
and Upland varieties have been raised for long periods in regions
where the boll weevil did not exist and, as was to have been expected,
are largely lacking in protective features. The Kekchi cotton, on the
other hand, which has continued its development in a weevil-infested
region under the protection of the keleps, has by far the largest
number of weevil-resisting characters.

The fact that weevil-resisting adaptations really exist, as ‘shown i in
numerous instances in the present report, emphasizes the necessity of
a thorough study of our cultivated cottons for the purpose of taking
advantage of any and all protective characters.

It is possible, as Mr. Cook suggests, that the Guatemalan variety
of cotton which he has discovered, and which has such a surprising
number of weevil-resisting adaptations, may not prove suited to culti-
vation in the United States, but even in that case the value of the
present paper on weevil-resisting characters would not be diminished,
for it will serve as a help to ali who may engage in seeking and
developing such characters in the types of cotton now cultivated in
our country.

Respectfully, B. T. GatLoway,
Chief of Bureau.
Hon. James Wrtson,
Secretary of Agriculture.

CONTENTS.

° Page.
PICO CO nee eer nN oe Sek Mg RE ge (ie th
Seleciyesnnuencerat phevbolleweeyal=2_- 4285 3 oe eke he el se aele 10
Generaliprotective Charactersis-o ss] <5 5 - s So e e 11
Dwarf habit and determinate growth of Kekchi cotton______.________- il
Walrad an GierICOkGhi COpUOR 222 s4-- .- oS 222. ben ceseeedans 15
Effects of Guatemalan conditions on United States varieties. .____- uy
Acclimatization of Kekchi cotton in the United States _____. _____- ily
Early bearing facilitated by long basal branches -_______-________- ts 19
Barly rejection supertiuous squares 4. --.--2--- 2.2. -25.222-2-=-2- 20
Seasonal bearing of perennial varieties _____..._._.______--- ee ah 23
Annual cutting back of perennial varieties__.__..._._.______-_____- ae 24
amaeulks and leak Rheme. 20.2.2. Lb. i222 2S bee) 2 LeeLee esate: 25
inendentwoollsmecd 2 8 SP ee ee Be eats srerehs?. © dpe ore os CS 27
Extrafloral nectaries _____-_.__- Bee ee Nero ean eS = Es 28
INEGhanes Oleh Mes Caves sew tenes re ey Ae el ee Nok ae 30
tisxbernal mectariesjol thoanvolucre. -2. 745... 222. = 2) 8 31
Imnenmectaries Of thenmwoliGres= 2. 222) 22 2e Soe os coe ee 31
Nectaries of Guatemalan Sea Island cotton _____.___._.___-._____- 32
Continnedisecretion of nectar, 2-2 2-- --022. <2 2s ee eee 32
iBractletsisubtendine mnner mectamiess 2-2-2222. 225595 22222 22 8 33
Binciency.of the kelep protection. .=.=- =... 2.52 225.5. 20-22-2582 34
Other nectar-bearing plants visited by the keleps___._____._______- 36
Thewnyol ders as a pEOusGrIVGSLFUCtUTEe - -.. 2.2. -+- 22-24 oes ened eae 37
involucralibracts. crown together.) ._. .-...2-. .s< ee tesee ecb 2- ee 37
PAD PLESsCOhmManroinsiObabracthie=ee2e) eens eae ee Le ee 38
Warcesmnvollenesot Mekehitcottonas= ee 2. teas eee See eet 39
Opening, or flaring, of bracts avoided_..____..__..__._-_- ep Sa. 40
Hairy mere inst mmvoluerdl bracts= <2 82. - on occ eb tee E 41
EXtenpiOL prorechol by Involuere _. .222. 5.826. Se Se ee eek 41
thyailiaee Ob Openeiniy OlUGTEN (226) .08 sua. wR eae Soe oo ote 42
Bohai Ol) PAarasthiZzeG Wudss..- Bees h—e Sak es eed. ool s ache ke 43
pneudine Of weevil-infa@sted squares =. .....2..-2l.2: 524 -24--25--s eee 43
Countings of flared and fallen squares ____- Palen = eens gt pe eee 45
Proliferation of internal tissues of buds______.__._._..-.------. GELeeR 46
Causes and conditions of bud proliferation _.._._..........----._-.-.-- 49
Proliieranounm oper varieties|.=22 02... 5220 ..2-224 o2a2 S222 22822 Soe 50
Protec tignnion Ge MOls =. e888 ee 8 wale Et eres WA os 51
LBS SHS UELAVCIS GE LON, RES 0 Se a Se As ee 51
Immunity of very young bolls________- Oe OR ah a en RY See 52
HAIG OO WLOTOr y RUN OOM: = 8 ek ee LB ee 55
nick wall eagnolls Pewee saat ye aks 6 Ege Sod ie ea te ae 56
iourhlinines.of chamberpior bolls 2-222... 2.225222) cessed ose s- 56

5

6

Protection of the bolls—Continued. Page.
Proliferation from the wall of the boll.__--.--.--. - J. epee eae 58.
Time required for proliferation... ce. aes ee 60
Efficiency of adaptive characters: of bolls... ~~. --2. 722 0. eee 61
Bacterial diseases following weevil injuries________________.__.___-__- 62
Breeding in buds@derived*habitil. = 2022222 ee 62
Relation between proliferation in buds and in bolls -____________-____- 64

Protection of seeds by limt.-_. =.=. -==- 222. 2 De SASS er oe LS eee aCe 65
Protective seed arrangement in Kidney cotton ___._.______.._-______-- 66

Cultural: value of Kidney. cottone 2-2 9 =e ee ee 67

The nature and Causes of adaplations=~-.: 22 er-5 sees os eee 67

Conscious and unconse1ous:selection. 2. 2-2 28 ane ee eee eee 70

Summary of adaptations 222 29.0 52.22 co A a eee 72
Classification of adaptations. .22 =. /2 22232 2a ee eee 72
Adaptive characters of different types of cotton__.-._...---.._-.---_-- "3

Concludinotiremarks sss 2 - oe) = oo Sy Se ee eee 74

Descripiion of plates 22-- S22. O25: 2 Se tes re ees ee ee 78

Index. = <2 26. 2. PS ee ee ee ee 79

PLUS TRATIONS

PLATE I. Valley at Secanquim, Alta Vera Paz, Guatemala, the scene of
experiments with weevil-resisting cotton_--_-_--______- Frontispiece.

Il. Fig. 1.—Mature plant of Kekchi cotton. Fig. 2.—Kekchi cotton
plantewith: Dols. = 2 25 oA P 5. es eee ee eee eee 78
III. Involucres of Kekchi cotton, showing nectaries and bractlets___- 78

IV. Fig. 1.—Involucres of Rabinal cotton, showing connate and ap-
pressed margins. Fig. 2.—Open involucres of Egyptian cotton - 78

V. Fig. 1.—Young buds of Kekchi cotton with weevil punctures.
Fig. 2.—Buds of Kekchi cotton with proliferation_-_____._____- 78
VI. Large buds of Kekchi cotton with proliferation _ .___-._--_-.----- 78
VII. Weevil-infested bolls of Kekchi cotton ______.-.__-_-_---_- =a 78
VIII. Carpels of Kekchi cotton, showing proliferation -_____..____-_--- 78

IX. Fig. 1.—Kekchi cotton, successive stages of the boll. Fig. 2.—
Kekchi cotton bolls (right) compared with King bolls (left) - _- 78

X. Fig. 1.—Rabinal cotton with bolls. Fig. 2.—Bolls and seeds of
Kidney Cottons 3. O28 25 22 22 se 1 eee 78

CONTENTS.

B. P. I.—180.

WEEVIL-RESISTING ADAPTATIONS OF THE
COTTON PLANT.

INTRODUCTION.

The fact that Central American varieties of cotton have developed
weevil-resisting adaptations has already received preliminary notice.“
A third visit to Guatemala, in the spring of 1905, has given opportu-
nity for further studies of the protective characters of the native
varieties and for comparing them with the types of cotton now cul-
tivated in the United States. For this purpose plantings of Upland
and Sea Island varieties have been made in Guatemala, and as the
season advanced other tests of the Guatemalan and United States
varieties were arranged under very different climatic conditions in
Texas and at Washington.

These opportunities of comparative observation have revealed a
series of protective adaptations of such number and nicety as to fur-
nish a unique and well-nigh incredible instance of selective develop-
ment. The statement of the former paper may be repeated with
emphasis, that the presence of the weevil-eating kelep has enabled
the Indians of eastern Guatemala to maintain since very ancient
times field culture of cotton in the presence of the weevils, with the
result that there has been developed a dwarf, annual, short-season
variety with numerous features which, in the absence of sufficient
numbers of keleps, afford material assistance in protecting the crop
against the ravages of the weevil.

Whether this Guatemalan cotton can be made of direct use in the
United States or not, it demonstrates the existence in the cotton
plant of weevil-resisting characters. The new variety has lint of
good length and quality, so that its utilization in the United States
depends upon its adaptability to our climate and methods of culture.

As already explained in publications devoted to the kelep, the
weevil-eating propensities of that insect were discovered in 1904
during a visit to Guatemala which had been undertaken in the hope
of finding a weevil-resisting variety of cotton. It had been observed

a Cotton Culture in Guatemala. Yearbook of the United States Department of
Agriculture for 1904, 475-488; Science, N. 8., 20: 666-670, November 18, 1904.

y
‘

8 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

two years before that a field of dwarf cotton cultivated by the Indians
did not suffer from the boll weevils, though these pests were abundant
on a “ tree cotton ” a short distance away.

The kelep afforded an entirely unexpected and yet very striking
explanation of the fact that cotton was being grown as a regular
field crop in a region which had probably been infested with weevils
ror many centuries, if it were not, indeed, the original home of the
species. That there was an insect in existence specially qualified
by structure and habits to attack, disable, and devour the boll weevil,
was welcome news in the United States, and in accordance with cabled
instructions from the Secretary of Agriculture numerous colonies
of the keleps were brought home and colonized in the cotton fields
of Texas. ;

The finding of the kelep explained the failute of the weevils to
prevent cotton cultivations in eastern Guatemala, and seemed at first
to diminish the prospects of weevil resistance in the cotton itself.
Nevertheless, the intention of studying Guatemalan varieties of cot-
ton and the cultural methods in use in that country was not aban-
doned, and the results are not without bearing on the original ques-
tion of the causes of the apparent immunity of the Guatemalan
cottons, and also upon the more practical question of securing cotton
varieties and cultural methods by which the injuries of the boll
weevil in the United States may be reduced to a minimum.

The Guatemalan cotton protected by the keleps is a genuine Up-
land variety, very early and productive, with a fiber of good length
and texture, as already stated. In addition to features which di-
rectly favor the keleps, it has many other qualities which may
render it useful, even without its insect guardians. In former reports
it has been compared with the very early Upland varieties, such as
King and Parker; but comparative tests made in eastern Guatemala
show that the native variety, which it is proposed to call Wekchi,
vepresents a very distinct type of this important cultivated plant.
It belongs to Gossypium hirsutum, the Upland species or series of
varieties, in the sense that it is not a Sea Island, Egyptian, or Kidney
cotton,? but it is distinctly more different from any of the Upland
varieties now cultivated in the United States than these are from each
other. It has not been ascertained that the Kekchi cotton in its

«The Sea Island cotton is so called because cotton of this type is cultivated
on the Sea Islands of South Carolina, long famous for the excellence of their
product. The Sea Island cotton came originally from Barbados, whence also
its botanical name, Gossypium barbadense.

Upland cotton gained its name as a means of distinguishing it from the Sea
Island, being cultivated in the interior, or “ upland,” districts of the Southern
States. The Upland type of cotton was recognized as a distinct species by
Linnzeus under the name Gossypium hirsutum, but many subsequent writers

INTRODUCTION. 9

present form is suited to cultivation in the United States, but it has,
without any doubt, new and significant characters which must be
regarded as factors in cultural solutions of the weevil problem. (PI.
lie hie. 1:

Although cotton was not found to be planted as a regular field cul-
ture in any localities in Guateniala where the keleps do not exist,
small quantities are produced in the interior plateau region about
fabinal by what may be called dooryard cultivation, and these, too,
have suggested cultural factors and expedients which may not be
without practical bearing.

The present paper can claim to make only a beginning in the
bionomic study of the question, but it shows at least that the weevil
problem has many avenues of approach on the botanical side.

The cotton of Guatemala and neighboring countries has maintained
an existence, at least, in the presence of the weevils, and has suffered
an acute natural selection with reference to its ability to protect itself
against the weevil or to secure the assistance of allies, such as the
keleps. That no commercial cotton crop is raised or exported from
such districts does not prove that they are unworthy of scientific
investigation, or that they are not likely to yield materials and sug-
gestions of practical value in meeting the invasion of weevils which
is now so serious a menace to the cotton industry of the United States.

“Some of these weevil-resisting adaptations have been of use in
securing for the cotton the assistance of the keleps. There are others
which, if properly utilized, might render these interesting insects
unnecessary. Tropical America has been serving for thousands of
years, evidently, as a laboratory for this class of experiments. Texas
was invaded only yesterday—a decade ago. Now that we are forced
to engage in the strife, the first preliminary should be, it would seem,
to take stock of the weapons which nature has forged.

The present report was planned and partly written before the dis-
covery of the true nature of the best of the weevil-resisting adapta-
tions—the proliferation of the tissues of the buds and bolls. Some
of the characters here described may have no value except as sug-
gestions, but taken together they may be of interest as an outline of
the results of the very long period of selection to which the presence
of the boll weevil has subjected the Central American varieties of
the cotton plant.

lave erroneously confused it with the Old World species Gossypium herbaceum,
which is not cultivated in the United States, though often so reported.

The Egyptian and Kidney cottons belong to the Sea Island series, and are of
American origin. The Kidney cottons seem not to have been cultivated on a
commercial scale, but they are very widely distributed in tropical America. The
name refers to the fact that the seeds cf each compartment of the boll are
grown together into a small compact mass, in shape suggesting a kidney.

10 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

SELECTIVE INFLUENCE OF THE BOLL WEEVIL.

The bol! weevil exerts a most prejudicial effect upon the cotton
crop, but, unlike most parasites, it does not cause disease or debility
in its host plant. The young buds and bolls are merely pruned away,
as it were, the purposes of the weevil being the better served when the
plants remain vigorous and continue to produce more buds and bolls,
in which more eggs can be laid and more larve brought to maturity.
Nevertheless, if no bolls are allowed to develop no seed can be set.
The fate of the cotton crop in wet seasons in Texas shows that with-
out some form of protection the plant would have been extinct long
since in all localities reached by the boll weevil.

The long contact between the boll weevil and the cotton plant in
Central America has given ample opportunity for the latter to profit
by the selection which the insect itself has provided. Every differ-
ence by which a cotton plant was able to resist or to avoid the weevil
ard thus ripen more seeds than its fellows would give it a distinct
advantage, quite as if the selection were consciously carried on by the
planter or the plant breeder. The case is different from that of the
recent improvements of many of our cultivated plants by selection
for the increase of some particular quality already existing. Such.
improvements can often be made appreciable, or even highly valu-
able, in comparatively few years, but under the desultory Indian
methods of cultivation long periods of time would be required for
the origination and accumulation of such characters as these pro-
tective adaptations.

Climate and other local conditions must also be taken into consid-
eration. An adaptation which would be effective in one set of cli-
matic conditions may be of little use, or even a positive disadvantage,
in others, as, for example, the prompt shedding of the parasitized
buds. In a dry region the falling of a bud to the superheated,
sun-baked earth insures the death of the weevil larva, either by the
heat directly or by the complete drying out of the tissues in which
the larva is embedded. In the moist districts of eastern Texas, how-
ever, this expedient is quite ineffective, the larve often developing
even better when the buds fall off and he on moist soil than when they
remain attached to the plant.

It need not surprise us to learn also that the weevil-resisting adap-
tations shown by the Kekchi and other cotton varieties of Central
America are shared, to some extent, by those already known in the
United States, since the whole Upland type of cotton appears to have
been, originally, a native of the Central American region. Varieties
which reached the United States from Mexico and the West Indies
may, however, have had little or no contact with the weevil for many
centuries, while in Central America the struggle for existence has
remained severe and continuous down to the present day.

GENERAL PROTECTIVE CHARACTERS. Te.

It is now known that in the plateau region of Mexico the long dry
season effectually excludes the weevil, so that varieties of cotton from
the Mexican highlands, instead of being weevil-proof, as sometimes
represented, may have no immunity whatever when brought into
the much more moist climate of the cotton belt of the United States.

The Kekchi cotton of Guatemala, on the other hand, has to a much
greater degree than any of the varieties now grown in the United
States the very qualities which experiment has shown to be effective
’ for the mitigation by cultural means of the injuries inflicted by the
boll weevil. That it has, in addition, other features not possessed
by our United States varieties, or not hitherto interpreted as weevil-
resisting adaptations, need not be looked upon as anything outside
the normal order of nature, but is entirely in accord with what
appears to be the biological and agricultural history of the cotton
plant in Central America.

GENERAL PROTECTIVE CHARACTERS.

DWARF HABIT AND DETERMINATE GROWTH OF KEKCHI COTTON.

Although Guatemala is a tropical country and the climatic condi-
tions are suitable for the growth of cotton throughout the year, the
Kekchi cotton is cultivated only as an annual, and is smaller and
more determinate in its habits of growth than the Upland varieties
now known in the United States. It soon attains its full height,
and after a crop of bolls has set on the lower branches there is a
definite tendency to cease growing or producing new buds. The
later upward growth of the plants seems to be supplementary, as it
were, tothe formation of the bolls; often there appear to be no
more flowers formed, and many of those which come seem to be
undersized, as though the plant were really mature and were
«pproaching the natural termination of its existence. Our Upland
varieties, on the contrary, continue to produce throughout the season
hundreds of small squares on each plant which serve only as breed-
ing places for the weevils.

The explanation of the high development of these short-season
qualities of the Kekchi cotton is doubtless to be found in the custom
of the Indians, who pull up the cotton as soon as the bulk of the crop
has ripened to make room for the peppers, which are always planted
with the cotton. For the Indians the peppers are an even more
important crop than the cotton, so that when the time comes for
clearing away the cotton they do not wait for the plants which may
have delayed maturity. Late bolls, even, would never come to
maturity or furnish seed for planting. The result has been a very
long-sustained selection for early bearing and uniform ripening of
the crop. Some of our earliest Upland sorts may begin blossoming

pF WEEVIL-RESISTING ADAPTATIONS OF COTTON.

as soon as the Kekchi, but they show far less tendency to determinate
growth.

The development of earliness has been assisted, no doubt, by the
climatic conditions which prevail in eastern Guatemala. The rainy
season oftens begins before the cotton harvest is completed, so that
the later bolls are very likely to become diseased, or, if they reach
maturity and open, the lint is often beaten to the ground and made too
«lirty for use in spinning and weaving. In either case the seed is not
harvested.

The Indians believe that even if they did not pull the cotton up it
would not become a perennial, but would die out completely, even to
the roots, during the rainy season. Seeds scattered accidentally in
the plantation at harvest time are rotted by the rain and do not germi-
nate, so that little or no volunteer cotton is carried over from one
season to another.

If the Kekchi cotton were the only variety planted in Guatemala
and the weevil had there, as in the United States, no other food plant
than the cotton, the insects might all die off between April or May,
when the cotton 1s pulled up, and October, when the next crop is
olanted. There is, however, enough perennial “ tree” cotton in the
country to keep the pest from becoming exterminated. Moreover,
the question of additional food plants in Guatemala is still open.

The importance of securing short-season varieties of cotton for the
United States can hardly be overestimated, since, as already intimated
elsewhere,“ there is no longer any reason to hope that the more severe
winters of the northern districts of the cotton belt will give any pro-
tection against the weevils.

As long as the weevil was confined to the southern part of Texas,
where the cotton could survive the winter, the destruction of the
plants as soon as possible after the maturing of the crop was the only
measure calculated to seriously reduce the number of weevils. It
was also essential to plant cotton as early as possible in the spring to
avoid the weevils bred on the volunteer, or hold-over, cotton which
negligent planters had left in the ground. The extension of the pest
farther north and-the possibility of securing cotton varieties with
determinate habits of growth introduce several new considerations.
The hold-over cotton is eliminated from the problem, but in the more
northern latitudes, where the cold comes earlier and the temperature
remains lower throughout the winter, it may often happen that there
will be no period in which the weevils can be recluced by starvation,
unless time can be secured for this purpose in the spring by the plant-
ing of short-season varieties of cotton.

a Cook, O. F., 1905. Progress in the Stuuy of the Kelep, Science, N. S., 21:

052.

PROTECTIVE CHARACTERS OF KEKCHI COTTON. ali

Instead of colder winters being unfavorable to the weevils, there is
every probability that cold sufficient to keep them in a torpid, inactive
condition will preserve their noxious lives much better than warm and
pleasant weather, which enables them to continue active and thus
deplete their vital energies. The winter of 1904-5 was one of un-
precedented severity in Texas, both in absolute temperature and in
continued cold and wet, and yet the weevils were able, in many locali-
tiés, to infest heavily the early plantings of cotton to a far greater
extent than in previous years.

The farther north the locality the more will the efficiency of cul-
tural methods of avoiding the boll weevil depend upon the plant-
ing of quick-maturing varieties of cotton. It is true that in a
favorable season the cotton planted first would set its crop soonest,
and thus escape a part of the damage suffered by adjoining fields
of later growth, the earlier fields breeding weevils to attack in
larger force the later plantings. But instead of insuring a decrease
of the number of weevils in a given locality and checking the
propagation of the pest, very early planting by a part of the farmers
of a community might tend, after an early fall and a cold winter,
to the opposite result, since it would save the lives of large numbers
of weevils which would otherwise perish before the cotton, if sown
a few weeks later, would be large enough to furnish the weevils
with food. Dr. Herbert J. Webber states that planting could
probably be deferred even to the middle of June without impair-
ing the chances of a crop as large as that which can be obtained
in the presence of the weevil.

There would seem to be little object in planting cotton where
the weevils are as abundant as in some places in southern Texas in
the spring of the present year, 1905. Nevertheless, the opportune
occurrence of a few weeks of dry weather was able, even then, to
greatly improve the prospects of a crop. No matter how bad the
weevils, the planter still has hope that dry weather may come and save
his crop from being a total loss. As long as indeterminate varie-
ties are planted this possibility will always make it difficult to carry
out a general policy of early destruction of the plants.

Some of our Upland varieties of cotton are early enough in the
sense that they begin flowering and fruiting very promptly, but
unless the season is very dry they will produce a continuous succession
of buds until they are pulled up or frost cuts*them off. The earli-
ness of practical value is not to be shown merely by the date of
flowering, but by the date of ripening the crop of bolls and of
ceasing to form new buds in which weevils can breed. If the im-
provements noted in other parts of this report can be realized in
practice, it would no longer be necessary to destroy the cotton plants

14 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

in order to put an end to the breeding of the weevils. It would
then become practicable and desirable to regulate planting so as to
bring the growing period of the cotton at the most favorable season
for a rapid development of the crop, and thus to give the weevils
the shortest possible opportunities for breeding. If the fall and
winter had favored the survival of many weevils, planting could well
be deferred until the weevils had disappeared, a fact which could be
ascertained by starting early a few observation plants from which
the weevils could be carefully picked by hand as long as they con-
tinued to appear.

The extent of the mortality of the boll weevil in the spring has been
well shown in the investigations reported by Mr. W. D. Hunter on
the effects of applying Paris green to the very young cotton as a
means of destroying the weevils which had lived through the winter.
Numerous dead weevils were found in the poisoned fields, but equal
or even greater numbers were found in those to which no Paris green
had been applied, and the conclusion was drawn that a large propor-
tion of the weevils, which pass the winter in a state of hibernation
or torpidity induced by the cold, perish through starvation or other
causes in the spring, after the weather has become warm enough to
render them active again and permit them to renew their search for
cotton plants on which to feed and lay their eggs.’

It is easy to understand, too, that after the weevils have been re-
duced by the cold to a condition of inactivity involving an almost com-
plete suspension of the vital functions, the lack of food and the lapse
of time can make very little difference with them. Starvation comes
much quicker during warm weather while they are going actively
about, so that it is the autumn and spring which must be relied upon
to reduce the numbers of the weevils rather than the cold periods of
the winter months. Messrs. Hunter and Hinds have also noted as
significant the fact that of weevils captured at the middle of Decem-
ber, 15.8 per cent passed the winter successfully, while of another lot
captured a month earlier, only 1 per cent survived. Their conclu-
sions were as follows:

It is evident that the weevils which pass the winter and attack the crop of
the following season are among those developed latest in the fall and which, in
consequence of that fact, have not exhausted their vitality by oviposition or any
considerable length of active life.

With these facts in mind it becomes plain that no objections need
be raised on general biological principles to the introduction of new

aA determinate variety of cotton would also avoid the cultural disadvan-
tages incidental to very early planting, for if the weather happens to turn
cold and wet the cotton is often either killed outright and has to be replanted
or, what is still worse, it becomes permanently stunted and unproductive.

+ Hunter, W. D., 1904. The Use of Paris Green in Controlling the Cotton Boll
Weevil, Farmers’ Bulletin No. 211, U. S. Department of Agriculture.

VARIATIONS IN KEKCHI COTTON. 15

quick-maturing varieties of cotton from tropical countries on the
ground that cold weather will exclude them from the United States.
The early spring is the only time in which they will be likely to
encounter adverse conditions in this respect, and if varieties can be
secured which are able to mature a satisfactory crop in a short season,
these quick-maturing qualities will far more than compensate for any
lack of ability to withstand cold weather in the early spring.

The Kekchi cotton may prove, however, to be quite as tolerant of
cold as the other Upland varieties now cultivated in the United
States.¢ In its native country it is planted in October and grows
throughout the winter months in mountain valleys where tempera-
tures of between 40° and 60° F. are not infrequent. (PI. L.)

VARIATIONS IN THE KEKCHI COTTON.

Very great diversity of size, habit of growth, and other features
exists in the Indian cotton of the vicinity of Secanquim and Cajabon.
The plants cultivated by Mr. John H. Kinsler on the United States
system were also very different from any grown by the Indians,
being much more robust and compact than in the more crowded
native fields. The spreading lateral branches and low, compact
growth of the Kekchi cotton, as shown in Plate IT, figure 1, might have
cultural disadvantages if these tendencies were to be maintained in
regular field cultures. Such, however, is not likely to be the case.
When growing closer together the plants are more upright and less
leafy below.

To what extent the differences observed thus far represent varietal
characters can scarcely be determined without a field test of the
apparently different strains, side by side. The broken, precipitous
nature of the country renders it impossible to rely upon comparisons
of the conditions of the different fields.

The conservative agricultural habits of the Indians would tend to
the continued planting by one man or family of the same seed for
long periods of years, which might well conduce to the formation of
separate strains. The low germinating power of the seed may pos-
sibly be due to such inbreeding, though it is more likely that it deteri-
orates because of the humidity of the climate.’ Nevertheless, our
experiments were sufficient to prove that even among plants grown
from seed raised by the same Indian there were very appreciable

a This was shown to be a fact before the report was printed. See p. 18.

6 The Indians appreciate the fact that the cotton seed does not germinate well.
They are accustomed to plant six seeds together, from which two or three plants
usually reach maturity, often with one or two insignificant dwarfs underneath.
The yield per plant in these crowded fields is naturally very small, but the larger
individuals often bear from 20 to 30 bolls. At Rabinal from 6 to 10 plants in a
cluster is the rule, the product of the individual being still further reduced.

16 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

differences, sufficient to have a very practical bearing upon the ques-
tion of securing strains having the special characters required in the
United States. Indeed, there was nearly as much diversity among
the Guatemalan plants as among all the Upland varieties, though
these were In some cases unusually variable, as a result apparently
of the transfer to new and unwonted conditions of climate and soil.

The usual number of locks or cells in a boll of the Kekchi cotton is
four, but bolls containing three or five are not uncommon; often they
are on plants which have otherwise the usual number.

There is also considerable diversity on the same plant in the shape
of the bolls, some, for example, remaining quite conical and pointed,
while others round out to near the apex. One plant was observed
in which the bolls were very nearly spherical. The involucre was
also unusually large. The plant had an unusually deep red or black-
ish color, and was distinctly more vigorous than its neighbors, as
often happens with mutations.

It is not at all probable that a close selection has ever been prac-
ticed by the Indians, so that a wide diversity of mutational charac-
ters may be expected when once the variety has been brought under
careful observation.

The stems and petioles of the Kekchi cotton plant are dark red,
or at least spotted with red, and the leaves turn dull red with matu-
rity. The bracts and bolls are green when young, but with age and
exposure to the sun become more or less tinged or spotted with red.
The outer involucral nectaries also turn deep red, especially the two
upper ones, even while the buds are still very young. The great
majority of the leaves are simply three-pointed, but*many of them
have an additional smaller lateral point on each side near the base.

a@One plant at Secanquim showed a very decided instance of variegation
with white and red, though the latter color might have been due to an increased
tendency of the white portions to take the red discoloration common on normal
leaves. The lower branches of the plant show only normal green coloration,
and a part of the upper branches is also normal in color and size, and with
fruits rather above the average size. The variegated branches do not regu-
larly alternate, nor do they come all from one side, but they might still have
connection with the phyllotaxy. There seem to be two stages of the variega-
tion, a white and a light greenish-yellow ; the latter may belong only to young
leaves. Both are distributed with the utmost irregularity, and both may
affect the upper surface of the leaf while the under surface remains green, or
vice versa, though the latter condition is much less common than the former.
The etiolated portions of the leaves, involucres, and fruits do not attain the
full size of the corresponding normal organs, so that the parts affected are
more or less unsymmetrical, though where the variegation is slight this result
may be apparent, or if it be complete the symmetry is not affected. Except -
for two premature bolls the seed was not ripe, and these were from the nor-
mal lower part of the plant.

ACCLIMATIZATION OF KEKCHI COTTON. G(s
EFFECTS OF GUATEMALAN CONDITIONS ON UNITED STATES VARIETIES.

The behavior of the United States varieties under changed climatic
conditions in Guatemala is interesting in several ways. The “* King,”
which in the United States appears to resemble the Guatemalan
variety most nearly, here loses most of its distinctive characters and
breaks up into a variety of types, many of which would not be recog-
nized in the United States as at all related to King. One of these is
« “limbless” or “ cluster” variety, which for a time appeared to
Mr. Kinsler as a very promising new sort. It was smaller and dis-
tinctly earher than King plants of the normal type, and seemed
likely to be more productive, but only a few bolls developed, and
these proved to be of abnormal form, with deep grooves or notches
across the tip.

One of the features in which the change of climate seems to pro-
duce remarkable effects is that of earliness. The King, which in the
States is looked upon as the earliest variety, is found by Mr. Kinsler
to be somewhat exceeded in this respect by * Allen,” which has not
been looked upon as a competitor. The Sea Island and Egyptian
varieties, too, prove to be much more precocious than was expected.
Some of them begin flowering almost as soon as the Upland sorts.
The Rivers variety of Sea Island cotton, in particular, was very
early, robust, and productive, distinctly ahead of the near-by Janno-
vitch, though not so tall.

ACCLIMATIZATION OF KEKCHI COTTON IN THE UNITED STATES.

It was not unexpected that the Kekchi cotton would show a change
in its method of growth on being transferred to Texas. New condi-
tions of soil and chmate often cause notable disturbances of the
organism. Some of the tropical cottons planted in Texas for experi-
mental purposes have grown into large bushes without showing the
shghtest tendency to produce fruit or even flowers. In 1904 cotton
from Peru planted at Victoria, Tex., grew most vigorously to a
height of 18 feet, but remained quite sterile. It is possible, however,
that even in their own country these were what are called “ tree
cottons,” which usually grow to considerable size before beginning
to flower. Letters from Mr. Kinsler, in charge of our experimental
plot at Pierce, Tex., relate a similar behavior on the part of the
Kekchi cotton, which at that place has grown large and rank; but
toward the end of July it was beginning to fruit, so that the ripening
of seeds in Texas is to be anticipated.

Two or three years will probably suffice to diminish this abnormal
vegetative vigor, due to the stimulus of the new conditions, and per-
mit a return to the normal earliness of the variety. Similar results

9962—No. 88—05 M——2

18 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

have attended the introduction into Texas of Mexican varieties of
corn. The plants grew 14 feet high the first year and bore very little
seed; in the following seasons they became smaller, earlier, and more
productive.

The probability that the Kekchi cotton can be grown even at the
northern limits of cotton cultivation is strongly indicated by the
results of an experiment at Lanham, Md. (1905). In favorable sea-
sons cotton can be grown to maturity as far north as Washington, but
the present year has been very unfavorable, the summer months being
‘for the most part cool and rainy, and with several intervals of
unusually low temperature. The cotton, which was planted intention-
ally in rather poor soil, to avoid too great luxuriance of growth, ger-
minated very badly and remained small and stunted until August.
The Kekchi rows have, however, produced more plants, and more of
these have grown to maturity than with any of the domestic or for-
elgn varieties included in the test. The Kekchi type has also remained
more constant in Maryland than did the King variety when grown in
Guatemala, though there are obvious differences between individual
plants. Two plants in particular were found to have numerous buds,
some ready to blossom before any of the others had begun to show
signs of productive maturity.

It might be feared that a variety newly introduced from a tropical
country would be likely to suffer more from low temperatures than
our United States varieties, but this seems not to be the case with the
Kekchi cotton, even when the cold is carried down to the freezing
point. There were light frosts in Lanham about the end of Septem-
ber, just sufficient, as it happened, to do appreciable damage to cotton
in low ground. The Kekchi plants did not suffer more than the
American Upland varieties. The difference, if any, was in favor of
the Kekchi cotton, perhaps on account of the closer foliage.

Many annual plants, even those of tropical origin, are most vigor-
ous and productive at their northern limits of growth, not, as has been
supposed, because this is the coldest part of their range, but because
the heat and sunlight, necessary to plant growth, are greater during
our summer months than can be secured in a similar time in the
Tropics, owing to the much longer days of our northern latitudes.“

The Pachon cotton from western Guatemala, though it has grown
taller at Victoria, Tex. (52-79 inches), than at Lanham, Md. (30-40
inches), has produced numerous buds in Maryland, but none in
Texas. The Kekchi cotton also appears to have been more productive
at Lanham than at Victoria, to judge from a recent partial report
from Mr. Argyle McLachlan.

2 Cook, O. F., 1902. Agriculture in the Tropical Islands of the United States,
Yearbook of the United States Department of Agriculture for 1901, p. 367.

EARLY BEARING AIDED BY LONG BASAI. BRANCHES. 19

It is very possible, therefore, that if the Guatemalan variety is able
to thrive in the United States it will ripen its crop here in even less time
than it requires in Guatemala, and this is rendered the more probable
from the fact that in Guatemala the cotton has to be planted in the
‘ainy season and is obliged to exist for the first few months under
conditions of excessive moisture. The dry season of this district is
short and uncertain. For two years, 1903 and 1904, the Indians were
unable to burn their clearings, so that the corn crop failed and the
community was reduced to the verge of starvation. The cotton crop,
in normal seasons, is said to be planted in the latter half of October
and ripens in March.

The introduction of a dwarf, short-season cotton would require, of
course, something of a change in cultural methods in the South, since
the smaller size of the plants will need to be compensated by closer
planting. It will be readily understood that to secure the setting of
a crop in the minimum of time as many plants as possible should
be set at work. The question is not that of the maximum product for
each plant or for a given area. With the weevil in the field the time
factor becomes of chief importance.

Little is gained in reality by the rank growth of the larger varie-
ties; in fact there is a distinct loss in earliness, even though some
bolls are set in the early part of the season. If these are overshad-
owed and starved by the continued upward growth, the crop is delayed
and the lower part of the plant becomes, on the whole, distinctly
unproductive.

EARLY BEARING FACILITATED BY LONG BASAL BRANCHES.

The earliness of the Kekchi cotton is made possible by the fact that
the bolls are nearly all borne at the base of the plant, the upper
branches and their foliage serving merely to assist in bringing to
maturity the fruits which are set while the plant is still very young.

Like several other tropical economic species, such as coffee, cacao,
and the Central American rubber tree, the cotton plant has two kinds
of branches—the true or primary branch, which arises in the normal
position of branches in the axil of the leaf, and the secondary or fruit
branches, one of which arises at the side of each primary branch. In
most varieties only a few of the true branches are developed; often
none at all. They are almost always plainly indicated, however, by
a small bud or a stunted leaf or two, in case the bud has not remained
entirely dormant.

Cotton plants are either right-handed or left-handed in the sense
that on the same plant all the secondary branches come out on the
same side of the primary branches. It is possible, therefore, to de-
termine by its position whether any particular branch is a primary or

20 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

a secondary. But the function of the two sorts of branches does not
always remain as distinct as in the coffee and cacao. A primary
branch, like the main stem, never bears any flowers; it produces only
leaves and other branches, mostly secondary.

Secondary branches, on the other hand, produce normally a flower
bud at the axil of each leaf, and this rule holds very generally, except
that at the lower part of the plant it sometimes happens that a branch
which has the secondary position functions as a primary; that 1s,
instead of bearing buds and flowers it produces only leaves and sec-
ondary branches. In the Kekchi cotton, as grown crowded together
in the Indian fields, the primary branches seldom appear, but when
more space is allowed and the soil is fertile it is usual for two branches
to start from the axil of each of the lower leaves, one promptly pro-
ducing flowers, the other assisting in the rapid increase of the leaf
surface of the plant and of its power to elaborate food.

Under the popular idea that plants draw their food from the
ground the possession of branches which bear little or no fruit might
be looked upon as an undesirable character, but when we take into
consideration the fact that the leaves instead of the roots are the true
assimilating organs of the plant it becomes apparent that a variety
of cotton which develops its lower primary branches may have an
advantage in earliness over one which is obliged to depend for its
foliage upon secondary or fruit-bearing branches. In the matter of
determinate habits of growth these primary branches are also a fea-
ture, because they enable a plant to produce a full quota of leaves
without unduly increasing the number of fruiting branches and thus
continuing to add to the number of superfluous buds.

The most obvious characteristic of the Kekchi cotton as it grows in
our experimental plots is the long basal branches, which often equal
or exceed in length the main stem itself. The most prolific branches
of the United States varieties are those which come out from the main
stem at the height of about a foot, but the bulk of the crop on the
Kekchi cotton is borne much closer to the ground. (PI. II, fig. 2.)
The long basal branches facilitate the early ripening of a uniform
crop of cotton, but they will not be an advantage under all cireum-
stances; as, for example, in dry regions where the weevil can be held
in check by open culture. The necessary exposure of the fallen
squares to the full sunlight on hot, dry soil would be interfered with
by a plant of low spreading habit and dense foliage.

EARLY REJECTION OF SUPERFLUOUS SQUARES.

That the Kekchi cotton has a limited or determinate growth and
does not take advantage of the perpetual summer to become a tree or
even a large bush is evident from the fact that in the latter part of

BKARLY REJECTION OF SUPERFLUOUS SQUARES. 21

the season most of the flower buds and leaf buds blast and fall off
while still very young, before the weevil would give attention to them.
By the time the first of the cotton is beginning to ripen, most of the
plants have ceased flowering and no new leaves are being put forth.
Generally there are bolls only near the base of the plant.

It is a normal character of the cotton plant that the fruiting
branches shall produce a bud at each node or joint; that is, at the base
of each leaf. If all these buds were to be retained and treated impar-
tially to the food materials which the plant is able to supply, the
result would undoubtedly be disastrous, since the plant would-be able
to bring very few of its fruits to maturity, perhaps none at all, unless
a part of the burden were removed by the weevils or by other outside
causes.” It is under the necessity of throwing off a part of its load of
fruit at one stage or another of its development, the younger the
better.

The rejection is accomplished by the formation at the base of the
peduncle, or fruit stalk, of special layers of cells of soft texture,
which soon disintegrate and allow the bud or young fruit to fall off.
This is one of the many instances of the prodigality of nature, which
makes so many allowances in advance for the accidents which beset
the existence of all living things. The waste of buds is, perhaps, not
so large in proportion among the perennial “tree” cottons, which
form a considerable shrub before beginning to blossom. In cultiva-
tion, however, the tendency has always been to encourage early bear-
ing, and thus reduce the early vegetative period of the plant and
bring it to a precocious maturity. The result is that fruiting branches
are produced, even on young plants, and buds are formed out of all
true proportion to the actual productive power.

The habit of rejecting a large part of the squares and bolls is espe-
cially obvious in the “ cluster cottons,” varieties in which the branches
are abnormally shortened, so that the leaf surface of the plant is still
further reduced. This cuts down still more the productive power of
the individual plant, though there may be a gain in the number which
can be grown on a given area.

But cluster cottons have not learned to moderate their promises to
correspond with their powers of performance, and continue to set
vast numbers of buds, flowers, and bolls, which they are unable to
ripen. The same is true to a less obvious extent of all our Upland
varieties, but until the advent of the boll weevil the superfluous buds
were not a serious factor, and the waste under favorable conditions
was often well compensated by the power to recover and set a new

“In Texas it is believed that rain at the time of flowering reduces the crop to
half the normal quantity, or even less. The explanation given is that water
Settles in the flowers and prevents fertilization. This might serve as an addi-
tional indication that cotton originated in a dry climate.

29 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

crop when in unfavorable seasons the earlier buds were lost, or when, as
occasionally happened in southern Texas, there was a liberal top crop,
or second period of bearing, late in the autumn months.

The presence of the weevil alters all these factors. The superfluous
buds become positively detrimental, for they furnish the breeding
grounds for successive generations of weevils and enable the pest to
attain in the latter half of the season such numbers that a top crop
not only becomes utterly impossible, but a menace is prepared for the
cotton of the following year. For, although only a small proportion
of the weevils live through the winter, the number of survivors un-
doubtedly has a very practical relation to the supply maintained at
ihe end of the previous season, and this again is merely a question of
this persistent production of buds, now much worse than useless.

A short-season variety of cotton having a sufficiently determinate
habit of growth would by itself constitute a solution of the weevil
problem. The Department’s entomological investigations in Texas
indicate that it is only the weevils hatched in the last month of the
growing season—in October or November—which have a prospect
of surviving the winter. A cotton which ceased to produce buds
after July or August would remove the chance of wintering over
from all the weevils except the few that might develop in the bolls,
an almost infinitesimal number compared with those that now attain
maturity in the squares. Much would be gained, of course, if all
planters would promptly pick their cotton and then pull up and
destroy the plants, being especially careful to collect the infested
bolls. But to carry out efficiently such a programme is difficult and
expensive.

To what extent, if any, the Kekchi cotton will meet this need of a
short-season determinate variety, it is too early to form an opinion,
but the fact that it has these qualities to a higher degree than any of
the varieties hitherto known in the United States must be accepted
as evidence, at least, that the possibilities of this method of protection
have not been realized. In the latter part of the season the Kekchi
cotton ceases the upward growth of the main stem and its branches
and regularly drops the greater part of its buds before they are large
enough to be entered or fed upon by the weevils, and the analogies
to be drawn from the habits of other plants will justify persistent
efforts toward the development in this and in other stocks of the
habit of rejecting the buds still earlier or of not forming them at all
after the first crop of fruits has set. Many plants have, in fact,
exactly this habit so desirable in cotton; they continue to flower until
permitted to set seed.

SEASONAL BEARING OF PERENNIAL VARIETIES. 23
SEASONAL BEARING OF PERENNIAL VARIETIES.

The continued existence of perennial cottons in weevil-infested
countries, like Guatemala, proves the presence in these also of means
ef protection. One of the most important is, doubtless, the produc-
tion of an annual crop at a definite season, leaving the weevils with-
out opportunity to breed in the intervening months, thus greatly
reducing their numbers.

The popular impression that tropical plants take advantage of the
continuous summer climate and blossom continuously is correct only
for a small minority. Where there are definite wet and dry seasons
many tropical plants have alternating, periods of growth and rest
almost as pronounced as in temperate climates, and even in regions
of continuous humidity there are some species which shed their leaves
annually and rest for a time.

A further general reason for a simultaneous annual blossoming of
all the flowers of a species is undoubtedly to be found in the greatly
increased opportunities of cross-fertilization, just as many insects
swarm and many birds and mammals collect in flocks before the
breeding season. Simultaneous flowering is carried to a remarkable
extreme among the bamboos, where whole species grow for long series
of years without flowering, and then flower and die at once over long
distances and in spite of local diversity of conditions which might be
expected to advance or retard maturity.

Accordingly, while it would not be reasonable to insist that peren-
nial varieties of cotton have adopted the habit of annual flowering
only because of the boll weevil, the analogy of other plants may be
invoked to show that such a character can be brought about by select-
ive influence. The weevil could certainly assist in the development
of such a tendency, especially if there were a season of the year in
which the insects were less numerous, from climatic or other external
causes as yet unknown.

The tropical varieties of cotton are, as is well known, mostly peren-
nial, and some of them develop into trees of considerable size, the
trunk attaining a diameter of 6 or 8 inches, and the main branches a
length of 15 or 20 feet. The existence in Mexico of tree cotton
immune to the weevils has been reported, but as yet this has not been
substantiated. Possibly the weevil has not yet penetrated some of the
remote and arid parts of the republic. In eastern Guatemala, at
least, the tree cottons appear to enjoy no immunity from the weevil,
and at the time of the visit of the writer it was often impossible
to secure uninjured bolls, even as samples of the varieties. The
native cottons of the island of Cuba, according to Mr. E. A. Schwarz,
also have the habit of annual blossoming, in the intervals of which
the number of the weevils becomes greatly reduced. The cutting back

24 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

of the cotton by the Indians at Rabinal, as described in the next
paragraph, is an artificial means of attaining the same end, but the
native Sea Island cotton, found at San Lucas, and the Kidney cotton,
at Tucuru, are the best Guatemalan examples of this protective habit.

ANNUAL CUTTING BACK OF PERENNIAL VARIETIES.

While the annual variety of cotton protected by the keleps is the
basis of the only field culture found in eastern Guatemala, the Indian
population of the central plateau about Salama and Rabinal raise
small quantities of cotton in their dooryards by means of another
cultural expedient, apparently of great antiquity, as indicated by the
extent to which the plant is adapted to the cultural conditions. The
variety is perennial and has very small and inactive nectaries, pos-
sibly as an adaptive result of the dryness of the climate.

Most of the perennial varieties begin bearing only after the plants
have attained considerable size, but the Rabinal cotton is a notable
exception to this rule and avoids injury from weevils by the very
prompt flowering and fruiting of the new shoots.

The weevils are present in numbers, and are frequently seen crawl-
ing about on the plants in a leisurely manner quite different from
that which they affect in regions stocked with keleps. At the time
of our visit not a single boll or bud of any except the smallest size
could be found which had not been attacked by them. Nevertheless,
a crop of cotton is secured at another season. In the month of April
the Indians cut back all the bushes to the ground, and as the cotton
is always planted immediately about the doors of their houses, where
the chickens and turkeys congregate, the mortality of weevils at this
time is probably very great. The protection of the domestic birds
doubtless continues until the new shoots have grown out of reach.

As soon as the plants are a few inches high they begin flowering,
und before the weevils are sufficiently increased in numbers to become
injurious a crop has been set. Flowers and fruit are commonly borne
on the lower branches, only 6 or 8 inches from the ground. The
Indians say that if the cotton is not cut back, but allowed to grow
tall, they get no crop. The fact is that by that time the weevils are
too numerous to permit normal bolls to be formed. Our search for
such was quite In vain on both our visits to Rabinal. One boll which
gave no certain external proof of injury was wrapped up in a paper
and retained as a sample, but was overlooked in packing and not
transferred to the preserving fluid. When the paper was unwrapped
a few weeks later three dead boll weevils were found.

The Rabinal cotton crop is evidently not large, but the harvest is
said to be regular, and the area of fertile land in this district is so
small that none of it is wasted. Much foreign thread is now

HAIRY STALKS AND LEAF STEMS. oO

imported, however, for weaving in the native looms. The industry
has greatly declined in the last century, perhaps because chickens
have been generally substituted for turkeys, which were formerly the
only domestic fowl possessed by the Indians.

All attempts at establishing field cultures of cotton in this region
have failed. The local public, which does not take the weevil factor
into consideration, is firmly persuaded that cotton will not bear ex-
cept in the heavy, rich soil of the dooryards of the Indian villages.

HAIRY STALKS AND LEAF STEMS.

The weevil on foot is a rather slow-moving, clumsy insect, and it
has been ascertained in the course of the investigations conducted by
Messrs. Hunter and Hinds that its movements on the plants are to a
great extent impeded by hairy stalks and leaf stems. The smooth
Egyptian and Sea Island varieties were found to be more susceptible
to weevil injuries than the hairy Upland sorts. The Kekchi cotton
is still more hairy, however, than the United States varieties, and
gains an added advantage from this fact. The longer it takes the
weevils to cimb from one bud to another the greater are the chances
of their being caught by the keleps. The latter insects, owing to
their much longer legs and the claws with which their feet are armed,
are not only able to travel readily over the hairs, but find them of
definite assistance. On smooth surfaces they are much less adroit
in catching and stinging the boll weevils. In our experiments, too,
they seemed to prefer the hairy Upland cottons to the smooth Sea
Island varieties.

The difference between the two insects in this respect may also be
illustrated by the fact that the keleps are unable to ascend a perpen-
dicular surface of clean glass, a feat which the weevils accomplish
without difficulty.

That the Guatemalan cotton was more attractive to the keleps than
the United States Upland and Sea Island varieties planted in ad-
jacent rows seems to be indicated by a census of our plot experiment,
taken April 19 by Mr. Argyle McLachlan. Kelep nests were
found at the bases of 41 per cent of the plants of the other varieties,

@'Though distinctly hairier than our ordinary Upland varieties, the Kekchi
cotton is exceeded in this respect by two other Guatemalan types, as well shown
in a field test at Lanham, Md. The Pachon cotton obtained by Mr. William R.
Maxon in the Retalhuleu district of western Guatemala is distinctly more
hairy than the Kekchi variety, though it seems to be lacking in other weevil-
resisting features. The inyolucral bracts are not closed any more than in the
Sea Island or Egyptian types. The most hairy cotton of all is the Rabinal
variety, at least in the form it has taken at Lanham. The plants are very much
more robust in every respect than at home in Guatemala, and the hairy covering
shares in this increased vigor.

96 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

while 76 per cent of the plants of the Kekchi cotton were favored with
kelep nests. This apparent preference may be somewhat exaggerated,
perhaps, in view of the fact that the plants were often farther apart
in the rows of the Kekchi cotton, the seed having germinated very
irregularly. Moreover, the superior attraction of the Kekchi cotton
for the keleps may not have consisted entirely in the greater hairiness
or the more abundant nectar. The compact foliage and spreading
lower branches of the Kekchi cotton give greater protection from the
midday sun, which the keleps utilize by greater activity in the middle
of the day.

With the Sea Island varieties it seemed obvious, however, that the
smooth stems, more open habit, and smaller supply of nectar result in
distinctly less attention from the keleps. From 9 or 10 o’clock on hot
days they foraged very little, and seemed to have quite disappeared
from these varieties, though still to be found in considerable numbers
on the stems of the Upland varieties and most of all on the Kekchi
cotton, which appears especially adapted for the comfort and con-
venience of the keleps.

It was noticed, however, that the keleps went much more often into
the involucres of the Sea Island and Egyptian varieties than into those
of the Kekchi cotton, for the simple reason, probably, that they can
get in more easily.

In the latter part of the season, after the weevils had gained a foot-
ing in this field, Professor Pittier noticed a very decided preference
on their part for the Egyptian varieties, though it seems certain that
this type of cotton had never been planted in the country before. The
partiality of the weevils might be explained, perhaps, on such grounds
as the relative absence of the keleps, and also the ease of access to the
buds of the Egyptian cotton allowed by the more open involucres.
However, a slight change of food or of conditions of growth is often
a distinct advantage to plants and animals, so that a direct preference
for a new variety as food might reasonably be expected, and similar
instances are known.

The greater hairiness of the stems and the presence of the keleps
may also explain why the weevils in Guatemala were seldom seen
walking about on the cotton plants as they do in Texas. On the
other hand, they take to wing very readily and seem to prefer to
alight in the open flowers, the only places on the cotton plants where
they are safe from the keleps.

The petals are so smooth that the keleps seldom descend into the
flowers, and when they do sometimes appear to be unable to climb
out. The petals of the Sea Island sorts are smooth even on the mar-
gins, sometimes entirely so, while those of the Upland varieties are
fringed with fine hairs well up on the sides, if not all the way round
the apex.

PENDENT BOLLS. On

The liability to capture by such an insect as the kelep may also
afford an explanation of the peculiar sedentary habits of the male
weevils, which often remain stationary in one involucre for long
periods, or as long as their food supply lasts. It is necessary for the
females to go about in search of fresh squares for egg laying, but
similarly active habits on the part of the males would subject them
to unnecessary danger.

PENDENT BOLLS.

The early bearing of the Kekchi cotton is made possible, as already
noted, by the unusual development of the lower lateral branches,
which often have a drooping habit, leaving the buds and bolls in
pendent position, intead of upright. There are several advantages
in this arrangement, one being that the instinct of the weevils leads
them to the upper portion of the plant. In a very badly infested
field without kelep protection, the only bolls which escaped the.
weevils were a few lying close to the ground on these lower pendent
branches of the Kekchi cotton. Only at the time of flowering does
the peduncle curve upward and give the flower its normal upright
position. Thus these drooping lateral branches of the cotton, which
seem to hide the buds and bolls away from the weevil, may be looked
upon as a short step in the direction of such phenomena as the
cleistogamous flowers of violets which remain buried in the ground,
or those of the peanut which, after flowering, burrow into the soil to
ripen their seeds.

The flowers of the cotton plant open in a more or less directly up-
right position, and this is retained by the boll in most varieties. In
the so-called “ stormproof ” sorts, however, the bolls hang down, and
this is looked upon by many planters as a distinct advantage, since
when the boll is ripe and open the rain does not beat into it and wet
the cotton or wash it out, but is shed by the protecting outer shell and
involucre. ;

On pendent bolls the external nectaries are brought upward, so
that there is no danger of an abundant secretion of nectar being lost
by dropping off. The surface of the nectary is papillate and has a
somewhat waxy appearance. The secretion often collects as a dis-
tinct drop. The nectaries are also more readily visited by the keleps.
and the young bolls are likely to be better protected by them. If
these remained upright, the weevils would be more likely to alight
and enter the involucre at once.

The drooping habit may have a mechanical explanation as the re-
sult of the weakness of the comparatively slender. lateral branches.
It is also to be connected, perhaps, with the habit of early flowering
and fruiting, since this would bring heavier bolls upon smaller and
softer branches which would be twisted over by their weight. In

28 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

the later and more upright varieties the flowers are not formed until
the wood of the branches has hardened and become strong and rigid.
Pendent bolls may thus be said to be incompatible with the cluster
habit, which is brought about by the abnormal shortening and thick-
ening of the lateral branches, which are able to hold their flowers and
fruits rigidly upright, except as they may be turned sidewise by being
crowded together. The cluster cottons, too, have the undesirable
tendency to an abnormal multiplication of squares and young bolls,
many more than the restricted leaf surface of the plant will enable
it to ripen. This superabundance of flowers and fruits gives, how-
ever, the greater encouragement to the weevil, and uses up vegetative
energy which could be better employed in the prompt ripening of the
bolls already set. It is no uncommon thing, however, for even half-
sized bolls of cluster cottons to die without any sign of external
injury or disease, while other varieties close by remain perfectly
healthy. The cause is probably to be found in inadequate nutrition,
but this might also be expected to give them increased susceptibility
to injury from parasitic enemies of every kind.

It is not unlikely, too, that the drooping habit may be connected
with the greater size of the inside nectaries of the Guatemalan vari-
ety. These are, as far as we have seen, larger than in any other
American variety yet known; but the Asiatic cottons, which have the
inside nectaries still larger and more active, are also more definitely
pendent. The involucre is grown together at the base, as though to
more thoroughly protect the nectaries from above—from the sun,
which would dry up the secretion, and from the rain, which would
wash it off.

The nectar is formed in great abundance, and Mr. F. J. Tyler, of
this Department, has called attention to the fact that the surface of
the nectaries of the Asiatic cottons, instead of being merely papil-
late, as in the American Upland varieties, has a covering of close-
standing fine hairs, to which its velvety appearance is due.

Finally, it may be remarked that for cotton with upright bolls the
inside nectaries are often an element of danger, since when the secre-
tion is abundant and is not removed it flows along the bases of the
involucre and may serve as a medium for the germination of parasitic
fungi or bacteria. Bolls are not infrequently found diseased around
the base, apparently from this cause.

EXTRAFLORAL NECTARIES.

The cotton plant is not without floral nectaries similar to those of
related genera, consisting of fringes of nectar-secreting hairs lining
the pits inclosed between the bases of the petals. The nectar serves,
doubtless, the same purpose as in other plants, the attraction of the

EXTRAFLORAL NECTARIES. 29

honey-loving insects through which cross-fertilization is secured.
It does not appear, however, that the floral nectaries of the cotton
have any connection with the problem of weevil resistance, although
the weevils seem in Guatemala to spend a considerable part of their
time in the flowers, which are indeed the only safe places for them
on plants protected by the keleps. It had been noticed from the first
that the keleps seldom visit the cotten flowers, and Mr. Kinsler has
learned a very adequate explanation of this fact, namely, that they
are able to climb out of the flowers only with considerable difficulty,
and sometimes remain imprisoned in spite of all their efforts to
escape.

The functions of the extrafloral nectaries of plants are, as far as
can be ascertained, similar to those of the floral nectaries to the extent
that they attract insects, but beyond this there is a fundamental dif-
ference; the floral nectaries and highly colored floral organs serve to
secure visits of flying insects and thus maintain intercommunication
and cross-fertilization between the different members of the same
species, in spite of the fact that the individual plants are rooted fast
in the ground. The extrafloral nectaries, on the other hand, attract
to the plants insects which will remain upon them as permanent resi-
dents, and this is the end secured by the extrafloral nectaries of the
cotton.

It may be objected by some that no use or benefit to the plant has
been ascertained in the case of many species which have extrafloral
nectaries and other insect-attracting devices. Much remains to be
learned concerning these marvelous biological specializations, and
there are two obvious alternatives which need to be canvassed before
belief in the adaptive nature of extrafloral nectaries and analogous
structures can be destroyed. The character and extent of many such
specializations show that they have existed for a long time. They
may have served protective purposes no longer apparent. The other
consideration is that some of the symbiotic specializations existing
between such plants as Cecropia and Acacia and their insect inhab-
itants have arisen through selective encouragement, much as the
special characters of our domestic plants and animals have been
developed. It may be sufficient, in other words, that the nectaries or
other structures be of use to the insects which have done the selecting.
It may seem absurd to think of bushes or trees as having been domesti-
cated by ants many thousands of years ago; but the wonder is no
greater than that ants and termites regularly maintained subter-
‘anean fungus gardens ages before mushroom culture was undertaken
by man. )

30 WEEVIL-RESISTING ADAPTATIONS OF COTTON.
NECTARIES OF THE LEAVES.

The midrib of each leaf bears on the under side an oblong pit,
from which a drop of nectar may often be seen to exude. This is
collected and eaten by the keleps, which are thus induced to visit
all parts of the plants, especially while they are still small.

The habit of collecting the nectar was not previously known to
exist among the insects of the family (Poneridz) to which the kelep
has been referred. Nevertheless, the fact is not open to question.
The process is easy of observation in even greater detail than with
the true ants or the bees, because the keleps do not, like these insects,
have the art of regurgitating their food. They merely lap the nectar
up to form a drop, which, protected by the widely opened mancibiss
is carried into the nest to feed the queen and the young.

Nectaries, or at least nectary-like depressions, are to be found
probably on the leaves of all varieties of cotton, though very small
and apparently inactive on some of the larger tree sorts. The
shape of the nectaries also varies greatly in the different species and
varieties, some being longitudinal, others transverse, and still others
crescentic or even sagittate. Some varieties have nectaries on the
three principal veins, and some even on five veins.

The leaf nectaries of the Kekchi cotton are to be found on the
midrib of the leaf about 1.5 cm. from the base. They consist of a
rather shallow longitudinally oval depression surrounded by a broad
‘raised rim. The midrib often appears distinctly narrower above the
depression than below it, as though there were extra tissues to supply
it. The secretion is quite active, nearly all the nectaries showing a
small amount of liquid, which sometimes spreads out on the adjacent
surfaces.

These nectaries furnish, as might be expected, a medium favorable
for the growth of molds or fungi, and there is often a considerable
network of dark-colored fungus mycelium creeping in and about the
moistened depressions, and with occasional erect, needlelike points,
which may be fruiting bodies.

«This was not true, however, of a Mexican “tree cotton” of the Upland
type grown in the Department’s experimental plots in Texas last year. Large
nectaries were generally present on three veins of each leaf, and the midvein
often had two. They were of the crescentic or sagittate type, but often
extremely long and distorted. Another Mexican tree cotton, with a different
type of lighter green foliage, suggesting that of Bixa, had nectaries only
on the midvein and these reduced to a narrow groove. ~The vein was not
thickened nor the margins raised. The two varieties were about as different
as could well be with respect to nectaries. Neither produced either flowers
or fruit, so that their true relationships were not to be ascertained,

NECTARIES OF THE INVOLUORE. dl
EXTERNAL NECTARIES OF THE INVOLUCRE.

The Guatemalan cotton protected by the keleps has three broadly
oval or reniform pits at the base of the involucre, one at the middle
of the base of each of the involucral leaves.¢ These are larger, deeper,
and more active than the nectaries of any of the Texas varieties as
yet observed, though there is very great diversity of size and nectar-
secreting activity. In some of the varieties these nectaries are
reduced to mere rudiments or are entirely wanting. The depres-
sion may be present, but with no secreting tissue. The variety nearest
approaching the Guatemalan cotton in having large and active necta-
ries is the Redshank, but the King and other relatec sorts also have
fairly large nectaries.

The drooping or pendent position of the bolls in the Kekchi cotton
may be correlated with the special development of these nectaries, as
already noted. In the middle of the day the keleps are not very
active, but the nectaries are sometimes full to overflowing. If the
bolls kept the erect position usual in the varieties cultivated in the
United States the nectar would frequently drop off and be lost, but
when the fruits hang down the cuplike nectaries are brought upper-
most and hold the liquid much longer.

The evolutionary origin of these nectaries is fairly obvious. The
bracts are to be looked upon merely as modified leaves, with nectaries
which have increased in size and activity as the leaves have become
smaller and more specialized.

INNER NECTARIES OF THE INVOLUCRE.

As though to induce the keleps to come inside the involucre and
thus more effectually protect the young buds and bolls against the
weevil, the Guatemalan cotton is also provided with unusually large
interior nectaries, alternating in position with those of the outer
series and thus placed opposite the edges of the involucral leaves or
bracts. These inside nectaries, like the outside ones, are larger and
more active than those on most of the cottons cultivated in the
Southern States, but the closing of the involucre and the devolopment
of the inside nectaries have been carried much farther in the Old
World cottons belonging to the species Gossypium herbaceum.
Here the external nectaries are quite wanting, but the internal ones
are enormously larger and heartshaped, and secrete nectar in such
quantities that it often flows out in the groove between the adnate

«Instances are occasionally found where only two nectaries are developed,
but such deficiencies are much less frequent than in other varieties of the
Upland and Sea Island series. The Rabinal cotton commonly has only two
external nectaries. The Old World cottons thus far observed have no nectaries
in this position.

fetta)

2 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

bracts to moisten the edges of the involucre. As yet, however, the
purpose of these adaptations in the Asiatic cottons is entirely
unknown, both the boll weevil and the kelep being absent in the
Eastern Hemisphere.

The botanical homology of the inner nectaries is somewhat different
from that of the outer. They correspond in all probability with the
nectaries which are found on the calyx of some of the species of
Hibiscus, but there the calyx is large and covers the buds and each
sepal bears a nectary near its middle.

NECTARIES OF GUATEMALAN SEA ISLAND COTTON.

A variety of Kidney cotton planted in small quantities by the
Indians at Trece Aguas, Guatemala, has the outer nectaries very
variable in size and commonly quite wanting.* The inside necta-
ries seem always to be developed and are unusually large, being ex-
ceeded, as far as known, only by those of the Asiatic varieties. The
nectar secretion 1s’also very abundant. No weevils were found upon
this cotton, nor any keleps.

On the other hand, the free-seeded Sea Island cotton found by
Mr. Kinsler in the San Lucas’ neighborhood, not far from the
kelep cotton culture of Secanquim, reverses again the tendency of the
Kidney cotton to the great development of the inner nectaries and
the suppression of the outer. The latter are, in the San Lucas cotton,
nearly always present, of rather large size, and of a red color. The
inner nectaries are often rudimentary or quite absent.

CONTINUED SECRETION OF NECTAR.

Our Upland varieties commonly secrete nectar only at the time of
flowering, but in the Kekchi cotton the quid continues to exude
until the boll is nearly or quite full grown, thus securing the protec-

a@This variety not infrequently produces flowers with only two bracts, closely
appressed, like a clam shell. In one such instance there were two nectaries at the
base of each bract, or, to be more exact, two separate nectaries on one side and
one partly divided nectary on the other, as though the nectary belonging to the
deficient third bract had separated into two parts and joined the other necta-
ries.

bThis San Lucas Sea Island cotton is probably the variety in which the
weevils were found abundant in 1902, when the first intimation was gained
that the Kekchi cotton had means of protection against the weevil. The San
Lucas cotton is attacked not only by weevils, but by another long-bodied in-
sect larva, evidently lepidopterous, that gnaws through the boll at the ends,
both from above and below, and eats out the seeds. Nothing of the sort has
been seen in the fields protected by the keleps. There was also noticed in this
cotton an occasional abnormality closely comparable to the navel orange.
Rudimentary parts like a small secondary boll were found in the middle of
bolls otherwise normal. The orange tree and the cotton plant belong, it may
be remembered, to related families.

BRACTLETS SUBTENDING INNER NECTARIES. et

tion of the keleps for a longer period. The temporary character of
the secretion in our United States sorts was reported by Professor
Trelease several years ago.

In Guatemala, however, the young bolls seem to be quite as effi-
cient as the flowers. It is even possible that this generosity on the
part of the plant is excessive, since if the number of keleps is small
they may find all the nectar they need on the lower bolls, and hence
lave less inducement to inspect other parts of the plant. Under
favorable conditions in Texas the cotton plant produces a much
larger number of flowers than in Guatemala, so that what is lacking
in quantity may be made up by numbers, in case it should become
possible to utilize the keleps in Texas.

RACTLETS SUBTENDING INNER NECTARIES.

The Kekchi cotton is distinguished from all our Upland and Sea
Island types by the more regular presence and much larger size of
a series of bractlets, a pair of which usually subtends each of the
inner nectaries. In other varieties these are either wanting entirely
or are rare and rudimentary.“ The bractlets are inserted somewhat
obliquely, with their margins in contact below the nectary.

Sometimes they serve to conduct nectar to the edge of the involucral
bracts, the nectar following along between the slender bractlets like
ink between the nibs of a pen, as though to coax the keleps inside the
involucre. This must happen rather infrequently, however, to judge
from the great irregularity in the size of the bractlets. Sometimes
they are half an inch or more long, and extend well into the angles of
the involucre, or even project outside. (PI. III.) Nevertheless. it

«Professor Trelease, who studied the American Upland varieties, appears not
to have found the bractlets in pairs. -He says: “ These glands (the inner nec-
taries) belong in reality to an inner whorl of three bracts, alternating with
the outer ones, but generally wanting. In stunted plants, especially as cold
weather comes on, one or more of these inner bracts may be found.” (See
Comstock, 1875, Report upon Cotton Insects, 324.)

The shape and position of the bractlets seem to warrant the suggestion that
they represent the stipules of the outer bracts instead of an independent inner
whorl of bract leaves which has first become specialized and then become rudi-
mentary. The suggestion has the further warrant in that it may help to explain
the numerous inyolucral appendages of some of the related plants, which range
about the number 9—that is, 3 leaves and 6 stipules. The normal number should
be 6, if the two whorls of leaves were represented. One of the Guatemalan
species of Hibiscus examined with this interpretation in mind seemed to con-
firm it by showing very often 3 of the appendages broader than the others,
though the total number varied from 8 to 11, with an irregularity quite compar-
able to that of the bractlets of the cotton. Even the bracts of the cotton some-
times vary, involucres of 2 bracts being found occasionally, and in rare
instances 4.

9962—No. 88—05 mM——3

3b4 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

may well be questioned whether these inner bractlets have remained
unusually large in the Kekchi cotton because they have a definite
function or because of the greater size and activity of the adjacent
nectaries.

A variety of cotton called Pachon, planted rather extensively in the
Retalhuleu district of western Guatemala, and likewise protected by
the keleps, is similar to the Kekchi cotton in many respects, including
the possession of these large stipular bracts subtending the inner
nectaries, but with the addition that the bracts are fringed with long
hairs, as though to hold the nectar the better. This may also be the
function of the hairs which cover the nectaries of the Old World
cottons

EFFICIENCY OF THE KELEP PROTECTION.

The special development of the extrafloral nectaries in the Kekchi
cotton has been noted in former reports, it being the nectaries which
attract the keleps to the cotton plant. That the kelep preys upon boll
weevils and protects the cotton crop was learned last year, but it was
still possible to question the practical value of this form of defense.
Such doubts would not have survived an inspection of our recent
experiments in Guatemala. A small field of cotton just outside the
kelep area was attacked by the weevils in such numbers that not a
single normal boll developed on any of the United States Upland and
Sea Island varieties. In the field protected by the keleps the weevils
obtained no footing until the plants were well grown and an excellent
crop of full-sized bolls had been developed.

To test the efficiency of the keleps as destroyers of boll weevils and
as protectors of cotton would be possible in Texas only by stocking a
large area with keleps—a difficult and expensive undertaking. No
small tract would give a fair indication, since the weevils from the
whole neighborhood would continue to come in, and, although they
might soon be captured, would be able to do vastly more damage than
would be possible if the whole region were stocked with keleps.

In Guatemala, however, it was quite possible to contrast a protected
with an unprotected piece of cotton by the simple expedient of plant-
ing outside the area occupied by the keleps. A more striking result
could hardly be imagined. For several weeks, during which the two
plots were under continuous observation, the one remained almost
entirely free from weevils and weevil injuries and set an excellent
crop, while in the other scarcely a flower opened or a boll developed.
The very few exceptions were on the concealed drooping branches of
the native Kekchi cotton.

The weevils became, indeed, too numerous for their own prosperity ~
and fed upon and destroyed the very young buds before they were
old enough to breed larve. Twenty-five fallen squares collected and

EFFICIENCY OF THE KELEP PROTECTION. : 35

examined from under the plants of the plot without keleps yielded
only 6 larve, or 24 per cent. They even attacked the young leaf
buds, as observed last year at Rabinal. .

A large proportion of the injuries were caused by feeding punc- ~
tures, but this only emphasizes the fact that the number of weevils
which migrated into this plot was sufficient for a complete destruc-
tion of the crop, and since the other experiment protected by the
keleps was much nearer to the fields of the Indians there is every
probability that the weevils would have been, if possible, even more
numerous if the keleps had not been at hand to catch them.

The unprotected plot was located at about one-quarter of a mile
outside of the belt of Indian cotton culture, on land not inhabited by
keleps. The weevils lost no time in finding the new field. Infesta-
tion was complete, and quite as destructive as in Texas, the weevils
being so numerous as to overcome whatever resistance the cotton
might have been able to oppose to smaller numbers of ‘the pests.
The Sea Island, Egyptian, and United States Upland varieties were
not permitted to produce flowers or even full-sized buds, and even
the native Guatemalan varieties shed their squares before the per-
sistent onslaughts of the weevils.

Cotton is regularly cultivated by the Indians in this immediate
neighborhood, and Indian plantings more or less infested with
weevils were to be found within short distances of the protected field.
Nevertheless, the keleps proved to be sufficiently abundant on this
piece of ground to completely exclude the weevils. There were
enough, indeed, to protect with apparent impartiality all the kinds
‘of cotton included in the experiment, but if the numbers had been
less and the plants had been closer together, as in the Indian fields,
we may be sure that those producing the most nectar would have
received the most protection from the keleps.

The weevils were seldom to be found in the plot stocked with
keleps as long as the Indian cotton remained in vigorous growing
condition, but about the time the Indian cotton ripened, the weevils
seemed to make a more determined raid on our field, and along one
side nearly every plant suffered somewhat, though the weevils
could rarely be found except in the open flowers, which seem
to be recognized as their only safe roosting places. In a week or
ten days there was a distinct falling off, so that very little damage
was being done, and there was another short interval of practically
complete protection. But after this a renewed onslaught began and
the-numbers of weevils gradually increased, the Upland and Sea
Island plants continuing to produce thousands of new squares in
which the weevils were able to breed, quite as in the United States.

That the keleps are definitely attracted to the cotton plants, as
stated in previous reports, is fully demonstrated by the fact that

36 - WEEVIL-RESISTING ADAPTATIONS OF COTTON.

- many of the colonies moved their nests to new burrows excavated
immediately at the bases of the cotton plants. In some parts of the
field the proportion of cotton plants having kelep nests established
about their roots reached nearly 75 per cent, whereas the chance
that the positions of the cotton plants which stood in regular rows
would coincide with those of kelep nests would not be one in hun-
dreds.

The success of this experiment would seem to justify fully the
suggestions made in connection with the first announcement of the
discovery of weevil-resisting adaptations of the cotton plant, namely,
that the protection which these Central American varieties had
been able to Secure from the kelep had afforded them an opportunity,
perhaps unique, of developing other resisting adaptations. The
Kekchi and other related cottons, though having no monopoly of
weevil-resisting characters, furnish, however, the only instance as
yet known to scientific observation in which a field culture of cotton
has been maintained for long periods of time under climatic condi-
tions favorable to the boll weevil.

In Central America, at least, the secretion of nectar by the cotton
is not a useless or meaningless function, as observers of the plant in
other parts of the world have sometimes supposed. The cotton 1s
not the only plant upon which the kelep can live, nor the boll weevil
the only insect upon which it preys. To secure the attention and
obvious preference of the kelep the cotton nas been obliged to put
forth the superior attractions provided by its numerous extrafloral
nectaries.

This additional proof of the value and efficiency of the kelep does
not affect, of course, the possibility of acclimatizing it in the United
States. A more extended search in Guatemala resulted in finding the
insects under a wide range of conditions, and at altitudes of from 200
to 2,000 feet. It lives and thrives, moreover, in soils very much drier
than those to which it was supposed last year to be confined. Last
year’s experiments in Texas indicated likewise that the kelep with-
stands drought much better than it does standing water in its burrows,
and care is being taken this season to locate colonies with a view to
adequate drainage.

OTHER NECTAR-BEARING PLANTS VISITED BY THE KELEPS.,

The honey-collecting habits of the keleps are not confined to the
cotton. Another favorite is a species of Bidens (2. pilosa) called by
the Indians “ tshubai,” which has considerable value as a forage
plant, being of quick growth and succulent texture.

The preference of the kelep for the tshubai as a second choice after
cotton was noted last year, but no explanation was found, though

THE INVOLUCRE AS A PROTECTIVE STRUCTURE. 37

the plant was searched for nectaries. It was noticed by Mr. Kinsler
that the keleps seemed to be giving especial attention to the midrib
near its junction with the veins of the lower divisions of the leaf.
Our lenses then revealed the fact that there are two minute raised
wings or margins running along the upper side of the midrib and
petiole, forming two narrow grooves in which the nectar is evidently
secreted. The grooves are also protected by a row of fine hairs which
project across them from the raised margin. The behavior of the
kelep thus receives a practical explanation, and the tshubai finds a
regular place next to the cotton among the plants protected by the
kelep. The nectar-secreting habit of the tshubai may also explain
its being eaten so readily by stock, and may help to give it standing
as a forage plant, in spite of its weedy and unpopular relatives.

A second member of the composite family often visited by the
keleps is the “ sajal,” a species of Melanthera (probably J/. de/toidea),
which also has local value as a forage plant, being eaten greedily
by horses and mules, even in preference to grass. No nectaries have
been found on this. A third composite, not vet identified, produces
nectar in small depressions at the base of the leaf on the under side.

THE INVOLUCRE AS A PROTECTIVE STRUCTURE.

Cotton is the only plant known to be attacked by the boll weevil,
and it is also unique among its relatives tn the possession of a large
leafy involucre. This may be a mere coincidence, or it may be that
the weevil has had a considerable influence in the development of the
involucre, depending upon the antiquity of the contact between the
insect and its host plant. The involuecre has, it is true, functions
other than the exclusion of the weevils, since it takes the place of the
calyx in protecting the young bud, but the reduction of the calyx
probably followed the enlargement of the bracts, instead of preceding
it. But however originated, the large bracts have, at the present
time, a definite value in the problem of weevil resistance. There are
several specialized characters which appear as though definitely cal-
culated to increase the efficiency of the involucre in excluding the
weevils from the young buds.

INVOLUCRAL BRACTS GROWN TOGETHER.

Both the Kekchi and Rabinal cottons frequently have the involucre
closed at the base, the three bracts being grown together, thus making
it impossible for the weevils to enter from below. In the Sea Island
and Egyptian varieties, as well as in some of the Upland sorts, the
bracts are not merely divided to the base, but they often have the
lower corners rolled back, thus leaving an open passage for the
weevils. The Rabinal cotton much excels all the other varieties thus

38 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

far studied in the extent to which the bracts are grown together at
the base. Sometimes they are united for a quarter or even a third
of their length. (PI. IV, fig. 1, and-Pl. X, fig. 1.)

APPRESSED MARGINS OF BRACTS.

In both of these Gu&temalan varieties the margins of the bracts of
voung involucres are firmly and closely appressed, in striking con-
trast with the Sea Island and Egyptian varieties, where the bud is
commonly exposed even when very young. This form of protection
is effective while it lasts, but in the Rabinal cotton the involucre is
too small, and the growth of the young bud soon separates the bracts
and permits the entrance of the weevil. The United States Upland
varieties are intermediate between the Sea Island and the Kekchi cot-
tons in the degree to which the involucres are closed and the margins
fitted together. A large proportion of the Upland involucres give
ready access to the weevils, while most of those of the Kekchi cotton
remain effectively closed for a longer period, as will be understood
after a survey of the other involucral characters which conduce to
the same result.

In one respect the firmly closed involucres of the Rabinal cotton
seemed almost like an advantage to the weevil rather than the con-
trary, for the insect is not admitted to the bud until it is about large
enough to furnish a place of development for a larva. The plant
having taken control, as it were, of this relation, the weevils have not
needed to possess an instinct against the destruction of young buds.
Those of the open involucred Sea Island varieties often were attacked
while still altogether too small to bring a larva to maturity. The
advantage of the closed involucres lies, no doubt, in the fact that they
shorten the period of access and allow some of the buds to escape
which would be punctured either for feeding or for egg laying if the
weevil has a longer opportunity. (PI. IV.)

The Rabinal cotton culture is that in which the plants are cut
back vearly to the ground. During the next month, or until the buds
begin to develop on the new shoots, the weevils have no breeding
places and nothing to feed upon except the leaves and leaf buds. In
patches where the weevils are abundant the leaf buds are eaten out
so persistently as to seriously interfere with the growth of the plants,
and the very young flower buds were also reached in some instances
by boring through the involucres. When attacked at this stage the
buds wither and drop off. They serve the weevils only for feeding
purposes, and their use in this way only postpones the time when
breeding can be resumed.

The cotton at Rabinal was often overrun by two species of small
black ants, identified by Dr. W. H. Ashmead as belonging to the

LARGE INVOLUCRES OF KEKCHI COTTON. 39

genera Solenopsis and Tapinoma.* There was no indication, how-
ever, that these afforded any protection against the weevils, although
they might, perhaps, act as watchmen and scare weevils away when
they happened to be present on buds or bolls where weevils had
alighted, like other small ants which have been reported as attacking
the boll weevil. The keleps belong in an entirely distinct category
in being able to sting and carry off the weevils and make regular use
of them as food. Instead of being of service to the cotton these
small ants at Rabinal were a distinct injury; the Solenopsis was
taking care of plant lice,’ which often infested the cotton to a
decidedly harmful extent. It continues and supplements the work
of the boll weevils in stunting and distorting the plants. When the
aphids are very numerous, the leaves are badly curled and growth is
greatly impeded.

-

LARGE INVOLUCRES OF KEKCHI COTTON.

The Kekchi cotton has the bracts of the involucre much larger in
proportion to the contained bud than the Rabinal cotton or than any
of our Upland varieties. The possession of larger bracts constitutes
a distinct weevil-resisting adaptation, since it permits the involucre
to be more effectively closed and the protection to be continued for a
longer time. Sooner or later, of course, the bracts must be separated
by the growing bud. The larger the bracts the longer the bud can
continue to grow before spreading the bracts apart. (PI. TX, fig. 1.)

Prof. H. Pittier, who had charge of the Secanquim experiment in
the latter part of the season, was especially impressed with the pro-
tective utility of the larger bracts of the Kekchi cotton, as shown by
the following summary of his observations:

The large size of the bracts in proportion to the floral bud is a very important
protective feature. In the Kekchi cotton the amplitude of these bracts is such
as to completely inclose the bud at-all times before the anthesis, and even in
cases when they happen to be slightly separated the occlusion is maintained by
the long hairs which fringe them on all sides. The length of these hairs con-
stitutes a serious obstacle to the progress of the weevils, whose tarsi can not
obtain a firm hold on the solid surface. I have seen them drop to the ground
after many awkward attempts to gain access to the squares, while on the other
hand the keleps did not seem to be impeded at all by the bristles.

«The material was not sufficient for a conclusive determination of the species.
Doctor Ashmead says: “ You have two distinct species of ants here. One, No.
1, belongs to the family Myrmicidse and is apparently the worker of Solenopsis
picea Emery; the other, No. 2, belongs to the family Dolichoderidze and is
apparently the worker of Tupinoma ramulorum Emery. I am sorry you did
not have the different sexes, so that I could make positive of the species. In
Solenopsis, as you probably know, there are four or five different forms, and it
is not easy to identify from a single form.”

b These have been identified by Mr. Theodore Pergande as Aphis gossypti, a

species well known in the United States.

40 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

To show the increased size of the bracts in the Kekchi cotton, I have carefully
measured over 250 squares of five of the most promising varieties of the Upland
species. The dimensions taken were the length of the floral bud, and the length
and breadth of the bracts. The table, in which these data are condensed in a
comprehensive form, shows a decided advantage in favor of the Kekchi cotton.

TABLE I.—Dimensions of floral buds and bracts of several varieties of cotton
compared.

| Kekchi. Parker. King Allen. Jewett.
tH he oH oH 4 oH oH oH he Gq | ay Cn par oH te
Length of | 5 i) So |° Saye aah fe ee cote oe NOS io) i)
floralbud | $9) 44/98/50] 4H /38/ Oa) oH Se] oa] else] 5a] oe /ae
(millimeters). 2c /S2 gs Suge say gslgs\43 Selioe/es|Seals sg
\a5| 2s @#/g5 Me Bk a5 Oba | Se g5|Ma| an a5 | we Su
haa coa oe 5 gies || StS |S BS | ar ls Bo geis Be 2
eg ke (aa ==) i pO =e I ek a I lhe
nium. nine nine. nine nevi. LNA MN.) NLL nm. mm
5 Giles Oo) OB) ROMS ee ee ee Ae Se et ee se eee eas ba a | ge el ee
(ih pager Le SSR) tos Bri teds|| CLO" Rees ae ees Lis 26a) 20a eRe eS a ee
G=1G ae 62) 39 B27 13 | Sl ez): 5) 33) 19) 18) 34) 2 3 | 38 | 26
(SRS Sr os 5} 42) 30) 16) 36) 24, 7| 34] 23] 10) 34) 22 2] 36) 21
i BSS be ee 3 | 42) 30 18 39 25 9 40 | 24 18 37 23 10} 39 | 26
VG" eo ae 4 42 )\ = 8 38 | 23 6 44 | 25 13 | 39 24 7 41 | 28
Sil ee eee 3:1) 40) 33 6 39 | 26 6 40 | 24 5 | 39] 25 5 | 39 | 30
19-2052 2S Pb? ON s ealp 4 ee: 4) 42) 26} 1) 49) 29 1 | 52 | 38
A Lain dis CE ae 1 St} 27 3 | 48] 26 i ey ge: £5 2 aed a a We 0 Ya 2) 47 | 34
ra ee Ss 3| 47 | 36 Daf BB) (Dau e519 Al 26 Ld gee lie 23 i | aay pe eet |
ry, aa 2) 42°) 30. Sit Dish epyleee se |eeeeralione ae 1; 82) 21 1 | 48 | 33
ie anes Cae ee eee 2 44 2 | 2) 40] 2 5 | 42 C25 (ee Fe ON By
Pea pe fyi ee ty Pe ee ee [Peete 2 rode a lal AOR sl op ete Vere Gu o¥ Lian [ore nega
Slate eet ee SE Es Cra aa Re DS lesa 000 Nens Ul Paeen| ae Pee LE FE ree ges he Uae IE ee |
Sei eee) Weng iC sl Pe Bree | ee nae a (a Wr IRE PS SSO ae 1| 42 | 32 |
Total 33 Ef |e ee a 7te Ml Pe pee) Bue 1 EP eee eeeeee 18. |eeeslesees Be sceesyee mers |
iy

The advantage is particularly notable with respect to the greater
width of the bracts, which enables them to remain much more effect-
ively closed at the angles. In the Parker, King, and Allen varieties
the bracts very seldom attain a width of 30 mm., while in the Kekchi
cotton the average width for all except the smallest buds is above

30 mm.
OPENING, OR FLARING, OF BRACTS AVOIDED.

The unusually large and well-closed bracts of the Kekchi cotton
have another practical use in keeping the bud from drying out, as
explained in the discussion of proliferation.

The external indication of this difference is that in the Kekchi
cotton punctured squares commonly do not open, or flare, by the
spreading apart of the involucral bracts, while among the Upland
and Sea Island varieties flaring is the regular rule. Quite a per-
centage of the squares of Abbasi, Parker, King, and other varieties
stand well open normally before any injury has occurred, but the
Kekchi cotton seldom or never exposes its squares before flowering.
The larger and broader involucre is also able to permit the protrusion
of the flower without losing the power of closing and remaining
shut for a considerable period after flowering, while the Parker and
King varieties often remain quite open, so that the young boll is
fully exposed to the weevils.

EXTENT OF PROTECTION BY INVOLUCRE. 4]

An example of the promptness with which weevil injuries cause
the involucres of our Upland cotton to open is well shown in a note
by Mr. McLachlan:

On August 8, at 2 p. m., a small cage was placed over a small plant of Parker
cotton, and 5 female and 2 male weevils were introduced. The plant possessed
86 squares, 4 flowers, and 9 bolls. The morning after the weevils were put
into the cage several of the squares had flared and one had fallen. It would
seem that the mechanical forces of the square are quickly affected by the work
of the weevils. Here, of course, the punctures were numerous, because of the
many weevils on the plant. Some of the squares were riddled with feeding
and egg punctures.

The buds of Kekchi cotton often recover from three or four punc-
tures, though they might not do so if these were all made at the same
time. But it often happens that squares with numerous feeding
punctures remain closed and wither up without flaring.

HAIRY MARGINS OF INVOLUCRAL BRACTS.

Tn addition to their larger size, the bracts of the Kekchi cotton have
the marginal teeth or lacinize more numerous and more hairy than
those of our Upland varieties and able to afford more of an impedi-
ment to the entrance of the weevils. The difference was very pro-
nounced in our experimental plot, where King, Parker, and other
familiar American sorts were planted beside the Kekchi. It is as
superior in this respect to the other Upland varieties as they are to
the Sea Island.

The Kekchi and Rabinal varieties, though both belonging to the
Upland series-and having many similarities, have also very distinct
differences, as, for example, in the present character. The small,
firmly appressed bracts of the Rabinal cotton have the marginal
lacinie few and small; sometimes the edges are nearly entire, or
merely toothed. The hairy covering is also reduced to a fine, short
coat, which can afford little or no impediment to the weevils.

EXTENT OF PROTECTION BY INVOLUCRE.

That the closed involucres do indeed contribute to the protection of
the young buds from the weevils became very obvious in one of our
experimental plots at Secanquim, located about a quarter of a mile
outside the belt of Indian cultivation of cotton. There being no
keleps to afford protection, the cotton soon became thickly infested
with weevils, and very few bolls were allowed to develop on any of
the plants. There was a notable difference, however, in the age at
which the buds were punctured. As already stated, the edges of the —
bracts of some of the Sea Island and Egyptian varieties separate at
a much earler period than those of the Upland varieties, and the

49 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

weevils commonly attack them in their very early stages, and even
while they are altogether too small to permit the development of a
weevil larva. It has been pointed out already by Messrs. Hunter
and Hinds that the smooth stems and petioles of the Sea Island and
Egyptian cottons render them much more readily susceptible to
injury by the boll weevil than are the Upland types, and if we add
to this the disadvantage arising from the later development and the
more open involucres the possibility of protecting the long-staple
cottons against the weevils seems small indeed.

Instead of being immune to the boll weevil, as at one time hoped,
the Egyptian and Sea Island-varieties seem to be most lacking in
weevil-resisting adaptations, as might, indeed, have been expected in
view of the fact that they have been developed in regions to which the
weevil has not yet penetrated. The Kidney cottons, which may. be
looked upon as representing the Sea Island type on the mainland of
the American continents, have, as will be seen later, a peculiar
feature of protective value.

ADVANTAGE OF OPEN INVOLUCRES.

It will be apparent from the facts already recited that the partly
closed involucres of the Sea Island and Upland varieties now culti-
vated in the United States serve little or no purpose in resisting the
boll weevil. On the contrary, they often appear to be an advantage
to the insect, serving, as they do, to hide the parasite from its enemies
and protect it against the application of insecticides or capture by
insectivorous birds.“

The great variation in the size and shape of the involucre in the
different varieties of cotton suggests the practicability of securing
sorts with open involucres or with these structures reduced to small
dimensions. If the weevils were to be caught by insectivorous birds,
like the Cuban oriole, whose weevil-eating habits have been discovered
by Mr. E. A. Schwarz, open involucres would be a distinct advantage.
It might then be possible also to apply Paris green or other insecti-
cides to young buds which are, except in the early spring, the
exclusive feeding places of the weevils.

The practicability of an open involucre will need, however, to be
considered from another standpoint. It must be ascertained whether
the young buds will bear full exposure. Unlike most of the related
plants, the cotton bud is not protected by a calyx. The involucre may
be necessary as a substitute, especially in dry climates. In humid

apr. H. J. Webber states that the desirability of open inyolucres has been
appreciated and that selections of Upland varieties with a view to the develop-
ment of this character have been made.

BEHAVIOR OF PARASITIZED BUDS. 43

regions, however, this requirement might be relaxed, and it is in such
places that the injuries of the weevils are the greatest.”

BEHAVIOR OF PARASITIZED BUDS.
SHEDDING OF WEEVIL-INFESTED SQUARES.

In a dry climate, like that of the Mexican plateau region, the drop-
ping of the squares in which the weevils have deposited eggs would
constitute a very effective adaptation. The weevil larve do not sur-
vive a thorough drying out of the squares. It is only in the arid
districts of Mexico that the cotton plant has shown its ability to
escape from cultivation and maintain itself without human assistance,
if indeed it be not in some places a truly indigenous wild plant, as
several botanists have reported. But in a moist region like the cotton
belt of eastern Texas this habit of the plant has no practical use,
since as many of the weevils die when the injured squares remain
attached to the plant as when they fall to the ground.

“Tt is generally true that squares seriously injured by the weevil sooner or
later fall to the ground. Some plants, however, shed the injured squares more
readily than do others. It seems to be a matter of individual variation rather
than a varietal character. Thus occasional plants retain a large proportion of
their infested squares, which hang by the very tip of the base of the stem.
Normally the squares are shed because of the formation of an absciss layer
of corky tissue across their junction with the stem. In the case of the squares
which remain hanging, the formation of this layer seems to be incomplete, or
else it becomes formed in an unusual plane, so that while the square is effectu-
ally cut off, it merely falls over and hangs by a bit of bark at its tip. In this
position it dries thoroughly and becomes of a dark brown color. Plants
showing 6 or 8 of these dried brown squares are quite common in infested
fields. Although exposed to complete drying and the direct rays of the sun,
the larve within are not all destroyed. * * *

“Tt seems a conservative estimate, therefore, to say that fully one-third of
these exposed dried squares may be expected to produce adults. Considering
the exposed condition of such squares this seems to be a very high percent-
age. * * * The observations made, however, certainly show that a complete

from western Guatemala, grown in an experimental plot at Lanham, Md., has
the peculiar feature of a large calyx, which completely covers the young bud
and extends above it into long, slender, hairy tips. It may be that this is to be
looked upon as still another weevil-resisting adaptation. The weevils would be
able, undoubtedly, to bore through the calyx, but the hairy tips might hinder
their access to the bud. ‘The bracts are much smaller and much more open
than in the Kekehi and Rabinal varieties, but the laciniz, or teeth, along their
margins are rather stiff and are clothed with numerous hairs, stronger and
more bristlelike than in the Kekchi and Rabinal varieties, and able to keep the
laciniz from closing together.. It may be that the greater rigidity of the lacinize
and the bristles gives better protection than the open position of the bracts
would indicate. The case is in reality quite different from that of the Sea
Island varieties, where the bracts are both naked and open.

44 WEEVIL-RESISTING ADAPTATIONS OF. COTTON.

drying of the square does not necessarily destroy the larva, and that a square
Imay undergo far more exposure to direct sunshine than had been supposed
possible Without causing the death of the larva or pupa within.” @

It is to be remembered, however, that such disconnected squares are
thoroughly dampened every night by the dew, and that a small
amount of moisture may pass out from the plant through the shred
of dead tissue. In either case the hanging boll might get more moist-
ure and less heat than if lying on the dry ground, exposed to full
sunlight. Suspended bolls are exposed to air temperatures only.

If no other means of avoiding the weevil becomes practicable a
great extension of the cotton production into the semiarid districts of
western Texas, Oklahoma, and even Kansas is to be expected. The
long days of the more northern districts will conduce to the shorten-
ing of the growing season, and if dry weather cuts down the yield the
loss is likely to be neutralized by more or less. complete protection
against the weevils.

These contradictory effects of the same adaptation depending upon
climatic condition may render necessary a complete differentiation of
the cotton varieties of wet and dry regions.

It is not improbable that the Upland varieties previously known in
the United States came originally from the more or less arid regions
of Mexico, where absence or very small developmént of the basal
branches keeps the ground from being constantly shaded and gives
better chances for the weevils to be killed by the drying out of the
fallen squares.

Our Upland cottons are undoubtedly of American origin, but the
region from which they came has not been ascertained. Some of the
Texas varieties are said to have been brought from Mexico. Coro-
nado’s Journal of the earliest Spanish exploration in Arizona and
New Mexico contains many references to the cultivation of cotton by
the Indians. There can be little doubt that the agricultural Indians
of the Gulf region also cultivated cotton, though no documentary
evidence of the fact seems to have come to light as yet.

It is highly probable that the original home of the cotton plant, and
of the boll weevil as well, was in a somewhat arid region, since it is
only under such conditions that the weevil would be effectually pre-
vented from increasing to the fatal degree of destroying its host
plant, and thus cutting off its only means of subsistence. On the
other hand, it was only in a humid country lke eastern Guatemala
that many of these weevil-resisting adaptations would be likely to
develop if, as now appears, it has required the selective influence of
the boll weevil itself to bring them to their present advanced develop-
ment. ;

a Hunter, W. D., and Hinds, W. E., 1904. The Mexican Cotton Boll Weevil,
Bul. 45, Division of Entomology, U. S. Department of Agriculture, pp. 78 and 74.

COUNTINGS OF FLARED AND FALLEN SQUARES. 45

The adaptive character of this habit of shedding the parasitized
squares seems to be confirmed by the fact that it depends upon the—
existence of a special layer of soft cells which readily break down
when the bud is injured. Many plants have such cells as a means of
shedding their fruits, but they seem not to be prevalent among the
relatives of the cotton. The cotton itself does not drop the ripe bolls,
and even the empty shell often remains long after the seeds are gone.

The drier the climate the more effective is the prompt shedding of
injured squares. Whether there are other adaptations thus especially
suited to dry climates 1s not yet known, our studies having been con-
fined mostly to humid regions.

Dr. Edward Palmer, who has spent many years in botanical ex-
plorations of the dry plateau region of Mexico and who discovered
that the boll weevil was a cotton pest, states that in several localities
where the cotton was formerly grown without difficulty the introduc-
tion of irrigation improvements has proved disastrous. With the
assistance of the moist soil the weevils are now able to reach maturity
in large numbers and complete the devastation of the crop, quite as
in Texas. The irrigated soil affords a situation favorable for the
development of the larvee in the fallen squares.

This is said to have been the case about Parras, and at Rio Verde,
below San Luis Potosi. The culture of cotton has declined also in
the “Huasteca Potosina,” the tropical district between San Luis and
Tampico, and on the Pacific side of Mexico, along the Santiago River
above San Blas, as well as about Tepic. Doctor Palmer saw cotton
growing in a wild condition in the fences at the old mission, San José
de Guaymas, 6 miles from the commercial port; again at Mulege,
Lower California, across the Gulf from Guaymas, the latter a much-
branched, prolific tree, producing a nankeen-colored lint. About
Guaymas cotton was formerly utilized by the Indians as tinder, after
being dipped in a solution of saltpeter. The same facts were observed
by Dr. lL. O. Howard in 1899 at San José de Guaymas.

COUNTINGS OF FLARED AND FALLEN SQUARES.

An attempt was made in connection with our Guatemalan experi-
ment to secure data on which a definite statement might be based
regarding the extent to which the different varieties were protected
by their involucral characters, but the problems are too complex to
be reached except by more elaborate statistical studies than were prac-
ticable at that time.

Countings were made, for example, of the flared and fallen
squares—that is, of those which it might be supposed that the weevils
have injured—and of the number of weevil larve, proliferations, ete.,
found inside them. The results in percentages do not agree, however,

46 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

with the facts obvious in the fields; indeed, they greatly misrepre-
sent them. Thus the percentage of weevil injuries in flared and
fallen squares does not appear very much higher in the Kekchi cotton
than in the Sea Island and Upland varieties; yet as a matter of
fact the squares of the Kekchi cotton seldom flared for any other
reason than weevil injuries, and much less often for this cause than
did those of other varieties. Many small squares of the Kekchi cot-
ton fall off, however, before they are large enough or open enough
to be attacked by the weevils.” This takes place in the other varie-
ties to a much smaller extent, but with them the apparent percentage
of weevil injuries among flared squares is much diminished, because
many squares stand open and appear as though beginning to flare,
even before the weevils have attacked them.

PROLIFERATION OF INTERNAL TISSUES OF BUDS.

The protection of the buds does not end with devices for the exclu-
sion of the adult weevils, nor with the rejection of those in which they
have laid their eggs. It is also possible for the plant to heal the
wound, and bring the injured bud to maturity by preventing the
growth of the weevil larva. Where the climate is dry the weevil
farvee in the rejected buds are killed, as already explained. The
humid climate alternative of the falling of the parasitized squares is
proliferation, the growth inside the bud of loose, watery tissue in
which the larva does not develop. Whether the larva is killed by
smothering, starving, or poisoning, or by some combination of these,
is not yet known. Starvation is a sufficient explanation, since the
material with which the larva becomes surrounded can be no adequate
substitute for the highly nutritious pollen grains on which the infant
larva would otherwise feed.

Proliferation is much more frequent in the Kekchi cotton than in
any of our United States varieties, as far as known. The first and
second punctures are commonly resisted successfully, but the third,
fourth, or fifth attempt may succeed in the development of a larva.
The proportion of weevil punctures rendered ineffective by prolifera-
tion was found to run well above 50 per cent, sometimes between 80
and:90.> (GPE WV.)

The promptness and efficiency of proliferation bear an inverse pro-
portion to the size of the buds. As the latter grow larger the mass of
anthers inside becomes less compact, and the other tissues become too

the Kekchi cotton were sometimes cut away at the base and left hanging in a
wilted condition. These were at first taken for flared squares as the result
of weevil injuries, but it was later ascertained that this was not the case,
though the true cause was not learned. The damage was done in the night.

PROLIFERATION OF INTERNAL TISSUES OF BUDS. 47

nearly mature to put forth new growth. If the presence of the larva
at this stage is sufficient to cause the bud to fall off, the development
of the parasite to maturity is well assured, the large bud affording
good protection and adequate food. ame

In the Kekchi cotton, however, such late attacks very seldom cause
the bud to fall off. Larvee developed in the larger buds are turned
out of doors, as it were, by the opening of the flower. The tendency
of injured buds to persist is notably greater than in the United
States, either because of some physiological difference between the
varieties, or because of the larger and more firmly closed involucres
of the Kekchi cotton, which keep the buds surrounded with a moist
atmosphere and protect it against drying out while the new tissues
are forming to heal the wound and encyst the egg. ;

In the closely planted Indian fields the squares seldom flare as in
the Texas varieties. They generally remain in place and continue to
grow until the bracts have reached nearly their full normal size. In
fields partially protected by the keleps the weevil larve do not
seem to develop in buds as small as in Texas. Proliferation may
partly explain this delay and also the more firmly closed involucres,
but in our unprotected plot the weevils were able by repeated punc-
tures to infest smaller squares and reach maturity in them, after they
had fallen to the ground.

The behavior of weevil larve inside the squares in Guatemala
seems also to differ appreciably from that observed in Texas where
younger squares are usually much more accessible to the weevils, and
are commonly punctured. In Texas the larve regularly grow to
maturity, depending for food upon the pollen, which is completely
eaten out. In Guatemala this very seldom occurs. Small squares
with well-developed weevil larvee are rarely found under normal con-
ditions, nor do the larvee depend upon the pollen as their principal
article of diet, as in Texas.

Several reasons for this difference may be considered. The first is
that the larger and more firmly closed involucre of the Kekchi cotton
gives the buds several days of protection, so that the average size
would naturally be larger. The examination of large numbers of
squares picked at random from the Indian cotton fields by Messrs.
Kinsler and McLachlan show also that a very large proportion of the
punctures are followed by proliferation, and that this means of pro-
tection is much more efficient in the younger squares. Another rea-
son must be sought, however, for the failure of the larve to eat the
pollen of the large buds where proliferation is less prompt and less
frequent. The impression might be gained that the pollen of the
Kekchi cotton is in some way not acceptable to the weevils, since even
when there is an abundance of pollen at hand they prefer to eat out

45 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

the style and central column of the flower, and thence down into the
ovary or young boll. After this has been consumed the larve return
to the upper part of the bud to finish the remainder of the pollen.

Nevertheless, this suggestion of a protecting quality in the pollen
itself can not be accepted with much confidence because the weevils
showed in numerous instances that they could live and thrive upon the
pollen of the young sqnares, quite as in the United States. This oc-
curred in the experimental plot where there were no keleps, and the
weevils were very numerous and persistent in their attacks. After
two or three punctures the squares flared and fell to the ground in
the usual manner, and in these the weevil larve were able to reach
maturity.

A more probable reason for the usual failure of the larve to eat the
pollen as freely as in the United States is furnished by the opinion of
Mr. W. D. Hunter, that the original habit of the weevil was to attack
the bolls, like related species of Anthonomus, which live upon various
kinds of fruits. If this be true with reference to the boll weevil we
may think of the Guatemalan members of the species as having
retained somewhat more of the ancestral habits which with them are
definitely useful, because the cotton variety with which they have to
deal has perfected, to 2 larger extent than the Texas varieties, the art
of proliferation.

As a further indication of the greater strength among the Guate-
malan weevils of the instinct of attacking the ovary of the bud
may be mentioned the fact that a very large proportion of the
punctures occur low down—that is, on or below the level of the apex
of the young boll. The larva commonly eats directly to the center of
the bud and hollows out the apex of the young boll. This habit
gives rather less opportunity for successful proliferation than in
Texas, because the cavity hollowed out by the larva hes below the
level of the staminal tube, the tissues of which are the most active
in proliferation. The Kekchi cotton shows occasionally another
form of proliferation not recorded from Texas, namely, that of the
base of the corolla. Sometimes this enlargement takes place in an
outward direction, forming a wart or protuberance on one side
of the bud, as shown in Plate VI. In other instances the direc-
tion is reversed and the ingrowing edges of the wound made by
the weevil fill the internal cavity and prevent the development
of the larva. The proliferation of the corolla, besides being less

aA new species of Anthonomus with habits closely identical with those of the
boll weevil, but parasitic on the pepper plant (Capsicum), has been discovered
recently in Texas by Mr. E. A. Schwarz. This gains an added interest from the
fact already noted that it is the regular custom of the Indians of Alta Vera
Taz to plant peppers among the cotton.

”

,

CAUSES AND CONDITIONS OF BUD PROLIFERATION. 49

frequent than that of the staminal tube, is probably also less effect-
ive, since the weevil larve could escape before it into the center of
the flower while the proliferation from the staminal tube grows
outward, as though to meet the intruder and keep him separated
from the more special organs.

The habit of the larve to seek the center of the bud and gnaw
off the style is responsible for the loss of large numbers of younger
bolls which have suffered no direct injury from the weevil. Even
though the larva be subsequently killed by proliferation or though
the flower drops off and carries the larva with it, the lack of polli-
nation must prevent the development of the young boll unless par-
thenogenesis takes place, which seems improbable.

Larve were found in several instances in nearly full-sized buds
about to open, and in another case a more than half-grown larva
was found inside the central column of an open flower. More or less
distorted flowers with unmistakable signs of previous proliferation
in the bud stages are commonly found in the Kekchi cotton fields.

Summarizing the results of the study of proliferation in the
Kekchi: cotton, it may be said that although the frequency of pro-
liferation in the young squares 1s very great, its efficiency in prevent-
ing the breeding of the weevils is somewhat less than might be ex-
pected in Texas, owing to the difference of food habits among the
weevils. If the Texas weevils are as consistent in their habits as
now supposed, the introduction of the Kekchi cotton or of a similar
proliferating variety might be of great benefit as a preventive
measure. The extent, however, to which it could be made to compass
the complete destruction of the weevil would depend somewhat upon
the degree, if any, to which they might return to the habit shown in
Guatemala of feeding upon the ovaries or boll rudiments rather
than upon the pollen of the young buds, an important and hitherto
unsuspected difference in habits between the weevils of Texas and
those of Guatemala.

CAUSES AND CONDITIONS OF BUD PROLIFERATION.

That the proliferation is occasioned by the injuries of the weevil is
too obvious to admit of doubt, but it may be of much practical
importance to learn the exact way in which the new growth of tissue
is brought about. The disturbing factor might be either mechanical
or chemical. The new growth may be a direct response to injury of
the weevils in feeding or laying eggs, or it might be stimulated indi-
rectly by the secretions of the young larva, or by chemical changes
or decay of the damaged tissue. A second mechanical possibility is
that of pressure developed in the young and rapidly growing bud.

9962—No. 88—05 m——4

50 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

The burrowing of the weevil relieves this pressure at one point, and
may thus furnish the exciting cause of the rapid growth in this direc-
tion of the tissue of the staminal tube.

It seems not improbable that a relation will be found between the
method of culture and the extent and frequency of proliferation.
Open-field conditions, with much bare ground about the plants, would
increase the daily exposure of heat and dry air, and this would con-
duce to the wilting of the punctured squares, which might then be
expected to flare and fall off instead of remaining to proliferate. The
result of weevil work tn our open-culture plots was obviously differ-
ent from that in the more crowded cotton fields of the Indians. On
the widely separated plants the squares often fell off and permitted
the larvee to develop, as in Texas, except that there was still a distinct
tendency on the part of the larve to attack the pistil and ovary first,
before eating out the pollen.

PROLIFERATION IN OTHER VARIETIES.

Proliferation is by no means confined to the Kekchi cotton, but
probably occurs, occasionally at least, in all the Upland and Sea
Island varieties. A noteworthy Guatemalan Sea Island cotton was
found by Mr. Kinsler in the aldea of San Lucas, a few miles from
Secanquim.” Both the buds and the bolls afforded fine examples of
effective proliferation. Even the Egyptian varieties showed a dis-
tinct ability in this direction. In one instance no less than 17 of 23
punctured squares of Jannovitch had proliferated, and 15 cases
seemed to have been effective.

Proliferation ceases to occur when the bud has become too large.
The anthers are no longer so closely packed together and the tissues
of the staminal tube are too nearly mature. By that time, however,
the style may be sufficiently developed to furnish adequate food.
It is well known, however, that the period of development of the
weevil larvee may be greatly prolonged, and this would seem likely
in the present instance, since the tissues of the styles must be less
nutritious than the pollen. The delay also would be advantageous,
since it would permit the young boll to become larger.

«This variety is peculiar in having about half of each seed covered only with a
very fine, short, bright bluish-green lint. The upper half bears the long white
fiber, and is smooth and black when this has been removed. Some of the
plants had excellent crops of bolls, unusually uniform in size and apparent age,
as though the habit of seasonal flowering were well accentuated. The variety
is evidently perennial and grows to a height of from 6 to 8 feet, but on the
ether plants the leaves, flowers, and bolls were much reduced in size. The
plants were all occupied by small black ants. On some of them no weevils nor
any indications of weevil injury were found, but others only a few rods away
were badly infested,

PROTECTION OF THE BOLLS. 51

But as the power of effective proliferation declines in the larger
buds another factor of protection comes into play. The later the
attack of the weevil the greater is the chance that the bud will mature
and the flower will open and turn the weevil larva out of its quarters
to die. And since buds commonly mature which have been attacked
while still young enough to proliferate, it is easy to understand why
attacks made in the later stages seem to be effective only in excep-
tional instances.

An element of uncertainty often attaches to the enumeration of
weevil injuries because of the difficulty of finding the egg or very
young larve of the weevil in the squares which have been only
recently attacked. This is especially true in small squares where the
anthers are still white and of about the same color, size, and general
appearance as the eggs. The possible error does not, however, mate-
rially affect the result, since it is to be expected that the same propor-
tion of bolls will proliferate and the same percentage of weevil
larve develop as in the squares which are far enough advanced to
show definite results.

PROTECTION OF THE BOLLS.

If it be true, as already intimated, that the original habit of the
weevil was to attack the boll instead of the bud, the opportunity for
the selective development of protective characters of the boil has
been greater. This suggestion seems to accord with the results,
since the boll of the Kekchi cotton has a series of protective characters
even more striking and effective than those of the involucre and the
bud.

PERSISTENCE OF FLOWERS.

As long as the flower remains in place the young boll is thoroughly
protected, the weevils having no means of access except by boring
through the withering tissues, which seems not to be attempted. In
the Kekchi cotton the flower falls only when detached by the swelling
of the young boll. This may also be true of other varieties. (See
re EX.) :

The frequent sequel of proliferation in the bud, as noted above, is
the loss of the young boll through lack of pollination. This is espe-
clally true in Guatemala, owing to the tendency of the weevil larve
to eat away the style. On one occasion Mr. Kinsler collected from a
field of Indian cotton 28 young bolls showing signs of debility. These
measured from 13 to 20 mm. in length, most of them about 15 mm.
None of the smaller bolls showed signs of weevil injury, but in many
of them the ovules were already shriveling up. A few punctures were
found in some of the larger bolls, and in some of these proliferation
had occurred. The development of the weevil larve to maturity

a2 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

seemed unlikely in any case, because the unfertilized ovules were
already withering.

Presumably there are various stages and degrees of fertilization.
Some of the stigmas of proliferated buds seem to have adequate
pollen, so that the bolls can develop normally, while others obtain
none at all or only a little. The persistence of injured flowers is
much greater. They may not fall off at all, and often remain at-
tached by the withered style to the boll when nearly full size.

It thus happens that injured flowers protect their young bolls
longer than the others, but in most instances such bolls remain small
or unsymmetrical, presumably as a result of inadequate fertilization.
It is quite possible, however, for normal bolls to develop occasionally
from weevil-infested buds which never open, for the style often
pushes through and becomes fully exposed, so that fertilization by
pollen from another flower might readily take place.

IMMUNITY OF VERY YOUNG BOLLS.

For reasons not yet ascertained, the weevils in Guatemala seldom
or never attacked the very young bolls. This may be due to a con-
servative instinct on the part of the weevil, like that which forbids
the laying of any additional eggs in a bud already parasitized. It
is not impossible, however, that the oil glands with which the sur-
face of the young boll is very thickly beset may have a protective
function. As the boll grows larger the glands do not appear to
increase In numbers, but become separated much more widely. On
bolls of the Kekchi cotton the oil glands are usually absent from a
distinct longitudinal band running down the middle of each carpel.
(Pl. VII.) A large proportion of the weevil egg punctures are
made along this naked band, although very few of them take effect.
The wall is thicker here, and the weevil in boring meets the tough
lining of the boll chamber at an angle, and is seldom able to penetrate.
If this interpretation of the facts be correct, the naked band consti-
tutes a veritable weevil trap, a device for inducing the weevil to
make its punctures and lay its eggs in the part of the boll where they
can do no harm.”

To ascribe a protective value to the oil glands is not unreason-
able in view of the fact reported by Messrs. Quaintance and Brues,

a¥Yunter, W. D., and Hinds, W. E., 1905. The Mexican Cotton Boll Weevil,
3ul. 51, Bureau of Entomology, U. S. Department of Agriculture. p. 7S.

bThis peculiarity of a glandless longitudinal band in the middle of each
carpel was also noticed in a variety of cotton cultivated by the Moqui Indians
of Arizona, grown in 1904, in the Department’s plant-breeding experimental
field at Terrell, Tex. The Moqui cotton is interesting also by reason of its
short, squarish, distinctly apiculate bolls, more like some of the Old World
cottons than are those of other members of the Upland series.

IMMUNITY OF VERY YOUNG BOLLS. 538

that the Egyptian cotton, the bolls of which are excessively oily, is
on this account immune from the bollworm.* The oil contained in
the glands has a deep-brown color, a sticky, molasses-like consistence,
a disagreeable, pungent odor, and a sharp, resinous taste, suggesting
turpentine or Canada balsam.

The development of the oil glands seems to be especially great in
the Egyptian variety known as Mit Afifi, and the glands are more
superficial. By slight pressure, or by drawing the nail across the sur-
face, the oily liquid is freely obtained. Most of the Upland varieties
have the oil glands much more scattering and deep set than the Egyp-
tian sorts, and it is not possible to squeeze the resin out of them in
any such manner.

On Redshank and other Upland types the resin glands are marked
by slight superficial depressions, but a cross section shows them to be
well below the surface, with several layers of chlorophyll-bearing
cells between. On the Egyptian sorts the glands are also set in de-
pressions, but the gland itself is very close to the surface, and makes
the bottom of the depression again convex, the superficial layer of
cells being very thin. It seems to break spontaneously in some in-
stances; at least there are frequently small spots of hardened resin,
and very slight pressure brings out the dark, gummy fluid. The
fingers receive a permanent brownish stain, which with the acrid,
biting sensation experienced when the liquid is applied to the tongue,
increases the probability that substances of a definitely protective
character are present. It is well known that many of the aromatic
oils are for some reason highly distasteful or even fatal to many
insects.

The Sea Island and Kidney cottons have the oil glands conspicu-
ously developed, like the Egyptian varieties, but the Old World
cotton (Gossypium herbaceum) 1s in this, as well as in other respects,
more nearly related to the American Upland cotton (Gossypium hir-
sutum). The Aidin (Asia Minor) variety of Gossypium herbaceum
has the oil glands rather small and deep set, with the superficial pits
rather shallow, more so than the Ceylon or Korean types.

Even the petals of the Guatemalan Kidney cotton found at Trece
Aguas” contained oil glands. The color of the petals was a uniform
pale yellow, without purple spots on the inside, but in the upper

@Quaintance, A. L., and Brues, C. T., 1905. The Cotton Bollworm, Bul. 50,
Bureau of Entomology, U. 8S. Department of Agriculture, p. 71.

’ The Kidney cotton at Trece Aguas is called paiyi, and seems to have little or
no relation in the minds of the Indians with the dwarf Upland cotton, which is
called nok. In the Secanquim district, only a few miles away, this name paiyi
(pronounced like the English words pie ye) is not recognized. Kidney cotton,
theugh apparently not now planted by the Indians, is not entirely unknown to
them. They call it simply che nok, or tree cotton.

54 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

half specked with minute brown glandular dots.“ The oil glands of
the bolls of this Kidney cotton are apparently quite as strongly devel-
oped as in the Egyptian varieties, or even more so. They are distrib-
uted very irregularly over the surface, and are not lacking above the
dissepiments, along the middle of the carpels. The position and
structure of the glands seem also to be the same as in the Egyptian
cottons. They are close to the surface and show as distinct black
spots, there being no green tissues over them as in the Upland and
herbaceum types.

IT am indebted to Mr. Guy N. Collins for the suggestion that the
present inefficiency of the oil glands as a means of protecting the
cotton from the boll weevil furnishes no argument against the
adaptation of the glands nor their development through the selective
agencies of the boll weevil itself. This fact is sufficiently obvious |
when once stated, but it is not commonly taken into account in con-
sidering questions of this kind. We may be sure that the gradual
development of a protective character like the oil gland would carry
with it a corresponding increase in the power of the weevil to avoid
or to endure the injury. The ultimate value of the device would de-
pend on whether the glands were able to keep ahead of the weevils
in quantity and distastefulness. The readiness with which the boll
weevils attack the Egyptian cotton renders it obvious that oil is now
no adequate protection, but the preference of the weevils for the un-
protected strips of the bolls of the Kekchi cotton indicates that the
weevils still dislike the oil, though they may have foiled the attempt
of the plant to protect itself in this way.

There are two attendant facts which under certain circumstances
might readily obscure the immunity of the young bolls. Many such
small bolls fall off, a particularly large number it seemed from our
row of Parker cotton, but an examination of these failed to show
anything in the way of weevil injuries, except such as had been in-
flicted while the bud or flower was still in place, the style and a
small apical cavity having been eaten away in numerous instances.
Many small bolls were to all appearances quite uninjured. They
may have been rejected by the plant as supernumerary, the plant
being unable to furnish the food material needed to bring them to
maturity, or they may have failed of fertilization as a result of
weevil injuries to the bud or from other causes, such as the absence
of bees, which were extremely scarce in the Guatemalan cotton fields.
The frequency with which the boll weevils were found inside the

aThe flowers of the Kekchi cotton are pure creamy white when young and as
long as they remain open. When old and rolled together they become a pinkish
red. They are not yellow or bluish at any stage. The stamens and pistils are
also nearly white, the latter with rows cf oil glands showing as small grayish
dots.

RAPID GROWTH OF YOUNG BOLLS. 55

cotton flowers and well dusted over with pollen suggests the possi-
bility that in this district at least they were. a not unimportant
agency of cross-fertilization. The performance of such a service by
the boll weevil would be comparable to the famous case of the yucca
and its moth, the plant being dependent for cross-fertilization upon
its insect parasite. The weevils eat the pollen from the bud; that
they visit the flowers for the same purpose seems highly probable.
The investigations of Messrs. Hunter and Hinds have shown, indeed,
that a pollen diet is a necessity for the complete sexual maturity and
reproduction of the weevils; if without buds to feed upon they
seldom copulated and never laid eggs."

RAPID GROWTH OF YOUNG BOLLS.

Mr. John H. Kinsler, who gave careful attention to the earlier
stages of the Guatemalan experiment, gained an impression that the
young bolls of the Kekchi cotton increased in size with a rapidity
distinctly greater than-that of the United States Upland varieties
planted alongside. It was not practicable to establish the fact by
carrying out a series of daily measurements, though it was possible
to ascertain from dated tags used in connection with the hybridiza-
tion experiments that the Kekchi cotton can grow bolls to full
size in less than a month from the time the flower opens. Plate LX,
figure 2, shows on the right two bolls of Kekchi cotton less than a
month from flowering. On the left are the two largest bolls from an
adjoining plant of King, the seed of both varieties having been sown
the same day.

Such an acceleration of the growth would be of very obvious utility
in lessening the period in which the danger of infestation is greatest.
A large proportion of the weevils found in adult bolls of Kekchi cot-
ton were in “locks” or compartments of diminutive size, showing
that the infestation had taken place while the boll was less than half
grown. Indeed, the weevils seldom seem to be able to affect lodg-
ment in bolls more than half grown, although numerous attempts
are made in fields where the weevils are numerous. The following
field note describes such an instance:

A boll showing many external marks of weevil punctures was found on being
cut up with care to have been attacked at least fourteen times. In five cases
the outer wall seemed not to have been penetrated, but in nine others there had

heen complete perforations. All of these had been closed, however, by prolifer-
ation from the inner surface, and no living larye were found.

Such persistent attacks, however, may finally induce a diseased
condition which interferes with the normal growth of the boll, even

« TIunter, W. D., and Hinds, W. E., 1905. The Mexican Cotton Boll Weevil,
Bul. 51, Bureau of Entomology, U. S. Department of Agriculture, p. 113.

56 WEEVIL-RESISTING ADAPTATIONS OF COTTON,

though the weevils be successfully resisted. Such injured bolls often
show a brownish discoloration of the interior tissues near the base
and connecting with the nectaries, which may indicate a bacterial
disease, to be discussed later. Sometimes this affects the walls only,
sometimes one or more seeds and the surrounding lint.

THICK-WALLED BOLLS.

In the Kekchi cotton there are considerable variations in the thick-
ness of the outer wall of the boll. Not infrequently the wall equals
or exceeds the length of a weevil’s snout, so that only the largest or
iongest snouted weevils would be able to make an opening into the
interior cavity. It was noted, also, that on the inside such bolls are
often quite free from these injuries or small larvee, though numerous
attempts may have been made. Large larve or pup may be found,
but these have come, obviously, from eggs laid while the boll was still
young. On some plants the development of large thick walls takes
place very promptly, so that a protective character of considerable
value might be obtained if this feature could be increased and ren-
dered constant. Early development of the thick walls was indicated
by the fact that the young seeds and lint did not fill the cavity, and
the seeds were still far from mature. Instances might be drawn
from other plants where the growth of the pod or seed vessels far
outruns the seeds at first, so that the development .of such a character
in cotton might reasonably be expected.

Even when a wall thicker than usual has been bored through, the
egg must be laid on the outside of the mass of lint which still inter-
-venes between it and the young seed, so that the larva’s chances of
development are greatly lessened. As will be shown later in the dis-
cussion of proliferation in the bolls, the instances are very numerous
in which, although the wall is penetrated, no further damage results;
either the egg is not laid or the development of the larva is pre-
vented by proliferation. In any event the boll escapes further
injury, and it is a very significant fact that in the dissection of a large
number of such bolls of Kekchi cotton scarcely any young larve
were found, in spite of the fact that most of them had been punctured
not once only, but many times.

TOUGH LININGS OF CHAMBERS OF BOLLS.

The three, four, or five chambers which contain the locks of cotton
in the unopened boll have each a complete membranous lining. In
the Kekchi cotton, at least, this is extremely tough and parchment-
like, even in bolls not yet full grown and in which the seeds are not
yet fully formed. This membrane is readily separable from the
more fleshy external layers of the boll, and though flexible, it is very

TOUGH LININGS OF CHAMBERS OF BOLLS. bi
firo. and incompressible, and resists tearing unless considerable
strength be exerted.

A large percentage of attempted punctures of the larger bolls
failed because the weevils are unable to penetrate this protective lin-
ing. This fact is readily determined by the study of radial sections
of the outer wall through the warts which mark the weevils’ points
of attack. The different texture of the new tissue which has closed the
wound shows, usually, that the cavity eaten out by the weevil extended
down to the tough basal lining, even when no evidence of the injury
has become apparent on the inside. In other instances, also very fre-
quent, the new tissue, developed as a result of the irritation of the
attempted puncture, exceeds the cavity and causes an inward swelling
or prominence of the inner lining analogous to the projecting warts
which are the usual external indication of weevil punctures.

Tt occasionally happens, too, that the projection of the new tissue
occurs almost entirely in the inside, the external wart being very
slightly developed or not at all, though the new tissue and the inner
swelling show that a puncture had been attempted.

The utility of this lining as a means of excluding the boll weevil
seems not to have been considered heretofore, and there has been no
opportunity as yet to compare the Kekchi cotton with other varieties
with regard to this feature.’ Certain it is, however, that in the Kekchi
cotton the parchment lining is almost as firm and tough as that which
surrounds an adult coffee seed. And it is certain, also, that a very
large proportion of the attempted punctures of the bolls failed to
bore through this inner wall of defense.

The examination of a large number of bolls, which were full size or
nearly so, though still far from maturity, in most cases failed to find
more than a very few instances, if any, of very recent perforation,
though there were large numbers of instances where the weevils had
enawed their way down through the parchment and deposited an
egg. In many such cases the proliferation or new growth induced by
the injury causes the parchment to be raised up from the wall on the
inside to form a blister-like, rounded protuberance. (Pl. VIII.)
Eggs laid outside the parchment are firmly embedded in the new

a Since this was written Mr. McLachlan has reported the existence of the same
form of protection in Upland varieties in Texas. The following note describes
the results of injuries inflicted upon the bolls of a plant of Parker cotton in four
days from August 8 to August 12, 1905:

“The 9 larger bolls, when opened, were found to have 28 weevil eggs deposited
in them; 6 had struck the dissepiment ; 12 were not entirely through the shuck of
the boll (either not more than half way there or else stuck in the tough inner tis-
sue of the shuck) ; the others were embedded in the lint. In only two instances
was there any proliferation apparent. The outer shuck had proliferated at the
wound and in one case had enecysted the egg. The other had merely forced the
egg to one side, haying begun the development too late.”’

58 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

growth and do not appear to hatch, or if they do the larve are not
able to do any damage, since they can not penetrate into the interior
of the boll. It quite frequently happens that eggs are laid in the
sinus or groove between the linings of two locks, but without penetrat-
ing the parchment of either. The tissue is here somewhat looser
than in other parts of the wall. In a few instances it was observed
that the larve had hatched, but no case was found which indicated
that larve hatched outside the parchment lining had been able to
penetrate to the interior cavity.

PROLIFERATION FROM THE WALL OF THE BOLL.

The wall of the boll offers an active form of weevil resistance by
proliferation, in a manner somewhat analogous to that of the pro-
liferation of the square. The channel excavated by the weevil is
closed by the new growth, which continues to push out on the inner
surface of the wall in the form of a rounded, blister-like protuber-
ance of loose tissue. This surrounds and encysts the weevil egg, and
prevents its development. <A section through the mass of new tissue
shows the egg embedded in it or pressed against the lint. _ Prolifera-
tion often takes place even when the tough lining of the chamber has
not been penetrated, and then appears as a prominence underneath
the membrane.

It has been seen from the preceding paragraph describing the
thick walls and tough lining that in the Kekchi ¢otton, at least,
the weevil is practically excluded from the boll after the boll has
reached about three-quarters of its full size; but even in its younger
stages also there is a measure of defense through the formation of
new tissue as a result of the irritation set up by the weevil’s injuries
in a manner analogous to that which induces the formation of galls
and other vegetable excrescences.

The first result of the proliferation is to fill up and heal the
wound bored out by the weevil. The cavity is not only completely
filled, but in most cases a wartlike prominence is formed on the out-
side, and if the parchment lining or the inner wall has been pene-
trated the new proliferating tissue also grows through on the inside
and often spreads out as a biscuit or button shaped protuberance
of soft white or transparent tissue several millimeters in diameter
and readily visible to the naked eye. (PI. VIIL)

There are two alternatives in the fate of an egg destroyed by
proliferation. Either it is completely surrounded in the proliferating
tissue outside or inside of the parchment wall or it is carried on
the apex of the proliferation down against the lint and flattened
between the growing surfaces. After the egg has disintegrated
and disappeared its position is frequently shown by a minute brown

PROLIFERATION FROM WALL OF BOLL. 59

stain. Such a discoloration often spreads back into the loose tissue
and then gradually extends over the whole lock of cotton of that
particular chamber. The seeds fail to develop and finally shrivel up.

If the proliferation results, as usual, in the death of the weevil
egg or young larva, the process of abnormal growth ceases with
the formation of a knob or button of the new tissue on the inside
of the wall of the boll. When, however, the young weevil escapes
destruction and continues to eat and grow, the proliferating tissue
also continues to increase, until in some instances the whole compart-
ment is filled with a silvery-white cheesy material which seems to
arise not only from about the original perforation of the outer wall,
but also from other parts which have been injured and irritated
by the presence of the weevil larva. This, with other facts already
stated, seems to show that in some varieties of cotton, at least, the
tendency to proliferation is very general, or, in other words, con-
stitutional, which warrants a larger hope of increasing this character
and making it uniform by selection.

When proliferation, which results from the presence of the weevil
larva, has become very extensive and fills the entire compartment,
the weevil larva is sometimes found to have eaten through the dis-
sepiment into the next chamber, perhaps to escape starvation. Such
extensive proliferation, accompanied by the failure of the seeds to
develop, means, of course, that the weevils gained entrance while the
boll was still very young. Moreover, if the boll had been older
there would have been plenty of food for the larva without the
necessity of entering a second compartment. Finally, the dissepi-
ment would have been too tough for the larva to penetrate easily.

Further proof of the fact that the weevil larve are seldom or
never able to gain a footing in the larger bolls is to be found in the
fact, already stated, that the weevil larvee found in them are nearly
always in undersized compartments, much smaller than those which
have remained uninjured, and have thus been able to continue their
normal development.

It is to be supposed, perhaps, that if the weevils could gain access
to large bolls and feed upon the nearly adult seed they would be able
to develop in less time than they usually spend in reaching maturity
on the rather poor provender they secure among the abnormal tis-
sues which arise after they have entered the young bolls.

The exclusion of the weevil from the large bolls has been evidently
not only an important measure of protection for the cotton, but it
has probably compelled the weevil to accustom itself to a gradually
longer and less prosperous development in the boll. The develop-
ment of the weevil-resisting adaptations on the part of the cotton
plant has left the insect with two opposite alternatives. It must
enter the boll early and submit to a very long period of development

60 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

or enter the square late and develop very promptly. The insect has
been able, as we know, to avail itself with a large measure of success
of both these alternatives, but it is not without encouragement for
future progress in weevil resistance to know that the plant has so
successfully guarded itself in two parts of its life history.

If additional evidence be needed to show that the food supply
obtained by the weevil larve in the bolls is very different from that
in the squares, it is to be found in the large, firm-walled cells of com-
pacted excrement with which they surround themselves in the bolls
before reaching maturity. The food being of a much coarser nature
and the period of development about three times as long, the amount
of waste material is naturally very much greater. If feeding upon
the boll is, as now appears probable, the ancestral habit of the wee-
vil, it need not surprise us that the protective adaptations of the boll
are more numerous and effective than those of the bud, which may
have been attacked by the weevil in comparatively recent times.

TIME REQUIRED FOR PROLIFERATION.

In connection with the experiments in Texas, Mr. McLachlan at-
tempted to ascertain the time required for proliferation to take place
after the injury had been inflicted. The amount of proliferation
and the time required for it to develop may be expected to depend
much on external conditions. Squares of Parker cotton showed no
development in six hours, but observation on bolls showed that pro-
liferation was complete in twenty-four hours. Two of Mr. McLach-
lan’s observations are described in the following notes:

On August 14, at 9.15 a. m., a wire cage was placed over a plant of King
cotton, and four weevils, of which at least two were females, were put inside.
Later, three more were introduced. At the time there were 11 bolls, 39 squares,
and 1 flower on the plant.

On August 17, at 1 p. m., 11 bolls and 18 squares were picked, a little more
than three days being allowed for the weevils to work. There was no rain, and
of the 18 squares examined only one revealed proliferated tissue, though the
weevils had scarred the buds in more than 33 separate places and had deposited 15
eggs. But the bolls showed better results. They had been scarred at 32 different
points, and 23 eggs were discovered when the bolls were cut open. In 12 cases
inward proliferation of the “ shuck” had destroyed the eggs. Several of the
incited growths had caught the egg, encysted it, and carried it along, inclosed
at the apex, as they pushed their way into the lint. As in the Parker cotton
examined a short time ago, weevils seem to have some difficulty in getting
the egg through the shuck of the boll. In dry weather it appears that the
King cotton is as backward as the Parker in proliferation in the squares, but
in bolls proliferation goes forward as well in dry as in wet weather.

On the 30th of -August, at 10.15 a. m., a boll (half grown and tender) was
bagged with a weevil. At 6 p. m. of the same day an egg puncture was found
on the fruit, but at 8 a. m. of the 31st no further injury had been inflicted. At
12 m., September 1, four more egg punctures were discovered, and the boll was

EFFICIENCY OF ADAPTIVE CHARACTERS OF BOLLS. 61
pulled and examined. The first puncture was then forty-two hours old and the
other four some twenty-four hours old. The examination revealed marked pro-
liferation in every case, with no greater growth in that of forty-two hours’
duration than there was in that of twenty-four. Hggs had been laid inside the
wall of the boll, since it was easy, in the case of young, tender fruit, for the
weevil to cut an opening to the lint. But every one of the five eggs had been
encysted by the proliferated tissue. It is quite possible that one or two of the
punctures reckoned as twenty-four hours old were still more recent.

EFFICIENCY OF ADAPTIVE CHARACTERS OF BOLLS.

The amount of protection afforded in Guatemala by the weevil-
resisting characters of the bolls might be greatly underestimated if
it were to be supposed that the weevils make numerous attacks upon
the bolls for the purpose of feeding upon them.

In their accounts of the habits of the boll weevil in Texas, Messrs.
Hunter and Hinds have devoted a chapter to * effects of feeding upon
squares and bolls,” “ but in Guatemala no indications were found that
weevils punctured the larger bolls for any other purpose than egg
laying. It is true that the outer surfaces of bolls are frequently
marked with scars of weevil punctures from which no larve have
developed and no internal injuries have resulted, but these failures
‘an be explained in other ways than by the supposition that the wee-
vils feed upon the tough and innutritious oviter walls of the bolls.
In Guatemala, at least, it appears that the weevil scars on large bolls
mark attempts at egg laying, though for a variety of reasons already
recited most of them are not effective. The only instance where wee-
vils were found feeding in bolls in Guatemala was at Rabinal. Two
weevils were together attacking a small boll, and had eaten out large
superficial pits, quite unlike the punctures in which eggs are laid.

Feeding punctures in bolls are referred to by Mr. McLachlan in a
note dated at Victoria, Tex., August 31, 1905. Such injuries were
not found, however, to lead to the formation of external warts which
could be mistaken for egg punctures, doubtless for the reason which
Mr. McLachlan gives:

It has been noticed that in bolls no proliferation occurs following the injury
from a feeding puncture, however serious that may be. Furthermore, from the
above and other observations it is apparent that proliferation is not excited by
the egg puncture or the egg, unless the puncture extends through the inside
tissue and the egg is fixed in the tissue or has been pushed through it to the
lint. In that case a dense knob of proliferation occurs on the inner side of the
shuck, in the center of which the egg is often encysted. There must be a con-
stant irritant like the egg, with an opening to give it access to the lint, in order
to occasion the specialized growth. As a suggestion it might be noted that all

the egg punctures are sealed by the adult weevil at the time of egg laying,
while the feeding punctures are left open.

«Hunter, W. D., and Hinds, W. E., 1905. The Mexican Cotton Boll Weevil,
Bul. 51, Bureau of Entomology, U. S. Department of Agriculture, p. 59, Pl, VIII.

62 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

The feeding experiment reported by Messrs. Hunter and Hinds “
shows that weevils fed exclusively upon bolls lived less than twenty
days, while those fed upon the squares lived nearly seventy days.
The bolls proved to be much less suitable for food than the leaves, on
which the weevils were able’ to prolong hfe for thirty days and
upward, though no eggs were laid on a leaf diet. It may be that in
Texas, where the army worms sometimes destroy all the leaves, the
weevils might be driven to gnawing the bolls for food, but in Guate-
mala the plants remain in full leaf throughout the growing season.

BACTERIAL DISEASES FOLLOWING WEEVIL INJURIES.

In the study of the bolls of the Kekchi cotton three diseased con-
ditions were observed, some or all of which may be of bacterial
origin, the bacteria having been introduced, perhaps, by the weevils
at the time of egg laying. None of these diseased conditions is fre-
quent, and as they do not permit the fruit to reach normal maturity
it seems very unlikely that they can be introduced into the United
States with the seeds. It may be stated in addition that the seed
obtained by Mr. Kinsler in the season of 1905 has been carefully
selected in the field and comes from the earlest and most vigorous
bolls.

The first of the diseased conditions consists in a white deliquescence
of the immature seeds and lint as though the lock had been dipped in
milk. There is also a distinct odor of fermentation. Another dis-
ease turns the seed and lint brown. Though observed only in bolls
which have been punctured by the weevil, there was often an
apparent connection between the disease inside and the large extra-
floral nectaries. A column of transparent or somewhat discolored
tissue extends from each nectary obliquely upward to the cavity of
the boll. This may be a symptom of the disease or it may indicate
that bacteria find their way into the bolls by way of the nectaries.

The third abnormal condition was also indicated by a brown dis+
coloration of the wall and contents of the affected compartment of
the boll. The seeds and lint soon die and shrivel. No special indi-
cation of bacterial activity was noted, and it may be that the death
of the weevil egg or larva has some prejudicial effect upon the sur-
rounding cells, as suggested by the brown discoloration already
noted in describing the effects of proliferation. Such a disturbance
inight continue to spread and thus cause the death of the young seeds.

BREEDING IN BUDS A DERIVED HABIT.

The fact that the weevil larve are found in the young buds of the
cotton plant and also in the full-grown bolls has been taken to mean
that it affects all the intervening stages as well. This would imply

a Hunter, W. D., and Hinds, W. E., 1. ¢., pp. 34-85.

BREEDING IN BUDS A DERIVED HABIT. 63

also that if the weevil fed originally upon the bolls it has followed
back to earlher and earler stages and finally to the bud. The facts
already detailed seem to prove, however, that this is not the case.
The weevil does not attack the very young bolls, nor does it operate
while the flower is open or while it remains in place, though in a
withered condition. The hatching of the weevil larva in the large
buds is likewise ineffective because the larva is deprived of shelter
when the flower opens. It seems necessary to believe, therefore, that
the parasitism of the weevils upon the buds of the cotton is a habit
quite distinct from that of its relations to the boll. The habit of
breeding in the bud marked a new departure in the biological history
of the insect and not a gradual change from the previous habit of
infesting the bolls only. Nevertheless, the change of habits need not
be thought of as anything very remarkable from the standpoint of the
insect. A cotton bud is very much larger than a small boll. The
peculiarity les in the plant rather than in the insect, since very few
plants afford a continuous and abundant succession of large, pollen-
filled buds. It is this quality of the cotton plant which has enabled
the weevil to develop its peculiar and highly destructive secondary
habits of feeding upon the buds and using them as breeding places.
If the boll weevil were restricted, like related beetles, to parasitism
upon the fruit of the cotton, it would have remained a comparatively
harmless and agriculturally insignificant enemy. These considera-
tions may assist in a better appreciation of the extent to which the
weevil’s power of injury would be: diminished if we could obtain a
variety of cotton with a fully determinate habit of growth, one which
would cease producing buds as soon as a crop of cotton had been set.

The much more rapid development of weevil larve in the bud is
to be connected, doubtless, with the much richer food offered by the
mass of pollen, but it may represent also a somewhat more definitely
adaptive specialization of the life history of the weevil, for it is gen-
erally a question of eating the pollen promptly or not at all. If the
bud falls off on moist ground the pollen would be completely decom-
posed long before the larva could develop, at the rate at which it
grows in the boll, and if the bud did not drop off, but continued to
grow, the flower would open and turn the larva out. It is obliged,
therefore, to do damage fast enough to keep the flower from opening,
and must then eat the remaining pollen before it spoils and leaves
the larva too hungry and stunted to pass through the final meta-
morphosis into the adult stage. In a cotton which has a highly
developed habit of shedding the injured buds it would not be so neces-
sary for the larva to attack the pistil. It may be that this policy
on the part of the weevils-in Guatemala has a use to the weevil as
being necessary to prevent the opening of the flower and cause the
falling of the bud.

64 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

The diversity in size of the boll weevils, while not unprecedented
among insects, is unusual, and not without biological significance in
the present connection. An explanation of the variation in size is
to be found, no doubt, in the varying amounts of food which the
weevil larve can obtain, but there is needed, none the less, a special
adaptability on the part of the weevil to permit it to reach a normal
reproductive maturity in spite of very unfavorable conditions. The
smaller weevils probably have less than a quarter of the weight of
the large ones, which means that they are able to develop with a cor-
respondingly small proportion of the food required to raise a full-
sized weevil. The weevils developed in the bolls have a much greater
uniformity of size. The small weevils are at once a means and a
result of the acquisition of the habit of living in the buds, and espe-
clally in the small ones, where the supply of food is often very small.

RELATION BETWEEN PROLIFERATION IN BUDS AND IN BOLLS.

The analogy of the mucilaginous tissue found in the young fruits
of okra and other relatives of the cotton would lead us to expect that
proliferation could occur more readily in the boll than in the bud,
which may mean that all the varieties which proliferate in the bud
will do so in the bolls as well.

It was at first supposed that if the buds proliferated but not the
bolls the result would be merely a postponement of the breeding
season of the weevil for two or three weeks, or until the bolls had time
to develop. Such a delay would be of great practical importance in
retarding for that length of time the effective breeding period of the
weevils. Moreover, most of the eggs of the weevils which had passed
through hibernation would be lost by being laid in the buds, which
would further keep down numbers in the early part of the season.
There is, however, the further and still more important consideration,
that the period of development of the weevil in the boll is very much
longer than required for it to mature and emerge from the square.‘

«Determinations of the length of the life cycle in bolls have been made only
in a few instances. In 7 cases between August 15 and November 11, 1903,
the average time required from the deposition of the egg to the escape of the
adult from the opening boll was sixty-one days. The average effective tempera-
ture for the period was 31.7° F., and the average total effective temperature
required for development in bolls was therefore 1,933.7° F., or nearly two and
one-half times as much as in squares. Several larvee often develop within a
single boll. ‘They appear to remain in the larval stage until the boll becomes
sufficiently mature or so severely injured as to begin to dry and crack open.
When this condition of the boll is reached, pupation takes place, and by the
time the spreading of the carpels is sufficient to permit the escape of the weevils
they have become adult.—Hunter, W. D., and Hinds, W. E., The Mexican Cotton
Boll Weevil, Bul. 45, Division of Entomology, U. S. Dept. of Agriculture, 1904,
p. 75.

PROTECTION OF SEEDS BY LINT. 65

Moreover, it seems that the adult weevil does not come out through
the wall of the boll, but waits to be liberated when the boll opens to
maturity. This would mean that if proliferation can exclude the
weevil from breeding in the squares it would afford a practical solu-
tion of the problem, since instead of merely delaying the emergence
of the first brood of weevils for two or three weeks, none of them
would be able to set about the work of destruction until the crop had
begun to ripen, and all danger of appreciable damage would have
passed. It seems, therefore, that the proliferation in the squares is
the much more valuable characteristic to be considered in seeking for
a weevil-resistant cotton. Proliferation in the bolls is very desirable,
but the absence of it should not be allowed to figure very largely
against a variety which might have a pronounced tendency toward
proliferation in the bud. Nevertheless, other factors must enter the
calculation, for thin-walled bolls might allow the weevils to escape
earlier. In moist weather the bolls might not crack open, but give the
weevils comfortable shelter all winter, as would seem to have been the
case in the spring of 1905, when various observers noted that some of
the weevils seemed to have the appearance of having emerged only
recently from the pupal condition, their very light color showing that
their outer covering of scales was still in place.

The probability is, however, that the proliferation in both places .
will be found to depend upon the same internal factor or quality,
so that it will be safe to assume that a high degree of proliferation
in the bud could be taken as an index of what might be expected
from the bolls. This would simplify the problem of selection by
permitting us to confine our attention to the buds.

PROTECTION OF SEEDS BY LINT.

Like the large leafy involucre, the lint is also a peculiar feature
of the cotton plant which may prove to have a practical connection
with the weevil. Cotton is the only food plant of the boll weevil,
and only the cotton, of all the related plants, has an abundant pro-
vision of lint. Some of the species of Hibiscus have the seeds
-shightly silky, but the cotton stands quite alone in the length and
abundance of the hairy covering which grows out from the seeds at
the time the bolls are most subject to weevil injuries.

From the standpoint of those who believe that all characters are
useful to the organisms which possess them, the interpretation of the
lint as a weevil-resisting adaptation will not appear unreasonable,
since it can scarcely be claimed that there is any other use of the lint
so important to the plant as protection of the seeds from the weevils.
In other respects the lint seems rather a disadvantage than other-

9962—No. SS—05 M 5

66 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

wise. In a humid tropical country the seeds, if left to themselves,
remain inclosed in the tangled mass of lint and usually rot. Birds
might carry the lint away to build nests, and in so doing might assist
in scattering the seeds, but in most of the varieties the seeds are to
be detached only with difficulty.

Composed as it is of nearly pure cellulose, the lint can afford very
little nourishment, even in the younger stages. Between thelint and
the watery proliferating tissue the weevil larva must find the imside
of a cotton boll a very inhospitable place unless it can penetrate to the
seeds. Dead and moribund larve are occasionally found in these
unfavorable situations. And even the seeds themselves do not pro-
vide so favorable a food as the pollen, as shown by the much longer
time required by the larve to develop in the boll than in the square.

PROTECTIVE SEED ARRANGEMENT IN KIDNEY COTTON.

Further intimation of the protective value of the lint 1s to be found
in the very peculiar Kidney cottons, so called because the seeds are
crowded together in the central angle of the chamber and adhere
firmly to each other, thus forming a small, kidney-lke mass. This
unique arrangement brings all the lint to the outside of the seed, and
may be the explanation of the fact that the Kidney cottons are the
only representatives of the Sea Island type which have gained a wide
distribution on the mainland. The separate-seeded Sea Island cot-
tons came from Barbados, where the boll weevil did not exist and has
not yet been introduced. (See Pl. X, fig. 2.)

The outer wall of the boll of the Kidney cotton is notably thinner
than that of Kekchi cotton, so that the beaks of the weevils could
reach through without difficulty. But with the layer of lint to sup-
plement it the wall becomes, for practical purposes, much thicker than
in the free-seeded varieties. The inner parchment lining is rather
tough, though apparently less so than in the Kekchi cotton.

The Indians about Trece Aguas, Guatemala, are said to recognize
the weevils as enemies of the dwarf cotton, but it is the local opinion
that the Kidney cotton is proof against them.

No weevils were found on the two bushes of Kidney cotton exam-
ined in that locality, but these were single plants growing near Indian
houses several miles away from the nearest field culture. In a forest-
covered country like this part of Guatemala the luxuriant and
tangled vegetation may well impede the flight of such an insect as the
weevil. And if it lives, as supposed, only on cotton, its chance of
reaching a single bush of tree cotton would be very small. That the
buds and young bolls of the Kidney cotton are able to offer any abso-
lute resistance to the weevil seems very improbable, and the abundance
of weevils found on the large tree of Kidney cotton at Tucuru last
vear proved that the immunity, if any, is not general.

NATURE AND CAUSES OF ADAPTATIONS. 67

The Kidney cotton, though commonly treated as a distinct species
under the name Gossypium peruvianum, agrees with the Sea Island
type in all its characters except the peculiar arrangement of the seeds.
If this should prove to be an adaptive feature the idea of specific
distinctness would have little left to support it.

CULTURAL VALUE OF KIDNEY COTTON.

The possession by the Kidney cotton of a definite weevil-resisting
adaptation would naturally raise a question regarding its cultural
value. It belongs to the Sea Island series, and has the long, fine fiber
and smooth seeds. The growing of the seeds together in masses would
still further facilitate picking and ginning operations. The bolls, too,
of this Guatemalan Kidney cotton, at least, are larger than those of
any of the Sea Island varieties.

It is not likely, however, that any of the varieties of Kidney cotton
thus far known will be found of use in the United States, for all are
perennial “ tree cottons,” which have refused thus far to flower or
fruit in the period of growth allowed by the shorter summers of our
Temperate Zone. In tropical regions this objection would not hold,
and there appears to be no reason why the Kidney cottons should be
disregarded in the search for varieties suited to the various soils and
climates. The Trece Aguas Kidney cotton, for example, seems to
thrive well in a humid mountain climate considered by the natives to
be unfavorable for the annual Kekchi cotton, which is planted several
hundred feet lower down.

THE NATURE AND CAUSES OF ADAPTATIONS.

To explain how such characters as the weevil-resisting adaptations
arise involves an interpretation of general evolutionary questions upon
which the scientific world is still by no means agreed. Nevertheless, it
is evident that students of such subjects should conduct and describe
their investigations in accordance with some consistent plan or
policy, if their writings are to be understood or their facts intelligibly
recorded. Moreover, it would be scarcely reasonable to maintain that
such characters can be further increased by selective influence unless
it could be believed that they had been assisted in the past by the same
agency.

It seems necessary to state that in the present report it is not
assumed that the weevil-resisting characters have arisen as direct pro-
tective responses to the injuries, or that they are the results merely of
stimulation or irritation caused by the weevils, as other writers on
evolutionary subjects might hold. Nor have they been thought of as
caused by selection in any strict sense of the word. Though consti-
tuting a most striking instance of the results of selective influence, it

65 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

is beheved that the cotton plant must first have originated in some
measure the protective characters before the external conditions (in
this instance, the weevils) could make them of advantage to the
plants and thus encourage their further development.

The older theory that environment and natural selection are the
efficient or actuating causes of evolutionary change has lost many
adherents in the last decade, especially among those who found
themselves unable to credit any longer the idea that all the characters
and differences of plants and animals are, or have been, of use to
them. It has been shown, too, by Professor Weissman and his fol-
lowers, that direct adaptations or responses of individual organisms
to the environment are seldom or never inherited by their offspring.
To take the place of the doctrine of direct environmental influence
in evolution it has been suggested that there may be an internal
“hereditary mechanism,” as it has been called, which determines
adult characters in advance, in the reproductive cells, so that modifi-
cations of the specific or varietal type can arise suddenly. Selection
would determine, of course, which of such new “ mutations” should
survive, but it would be a mere accidental coincidence if the new
character happened to fit the conditions better than the old.

It is possible, however, to explain evolutionary progress and select-
ive adaptations without ascribing them either to external causes or
to theoretical internal mechanisms. The diversity which plants or
animals of the same parentage often show under the same conditions
makes it evident that there is no precise mechanism which determines
their form in advance, and all attempts at securing any absolute uni-
formity or “ fixity ” of form and color have failed. The fact is that
organisms, even of the same species or variety, are normally diverse,
and must have ancestry mixed by interbreeding if bodily vigor is to be
maintained for any great number of generations.

The generalized “ specific type,” which is a product, as it were, of
this diversity and interbreeding, is constantly and gradually chang-
ing, and in many ways at once, though in some characters more rap-
idly than in others. Selection, while in no strict sense a cause of
this vital motion of the species or variety, may profoundly influence
the direction and rate of change. Selection, in other words, explains
adaptation, but does not explain evolution.? .

The word adaptation is used in more than one sense by writers on
biological subjects. Some treat as adaptations the changes of form
or structure by which many plants and animals are able to conform
to the needs of different conditions. There are several plants, for
example, which have normal broad leaves when they grow on land,
and very narrow and much-divided leaves when they grow submerged

a Natural Selection in Kinetic Evolution, Science, N. 8., 19: 549, 1904.

NATURE.AND CAUSES OF ADAPTATIONS. 69

in water. Some plants are hairy in dry localities, but are nearly
naked in humid districts. Others treat these direct responses to
external conditions under the heading of accommodation, and reserve
the word adaptation for characters which appear regularly in a spe-
“es or variety, but which fit 1t for some special condition, such as
that presented to the cotton plant by the boll weevil. It has seemed
proper, therefore, to discuss as protective adaptations any characters
which seem to give the Central American varieties an advantage in
withstanding the attacks of the weevil, particularly if it can be shown
also that the presence of the weevil would tend to the preservation
and extension of the given character.

In the strict sense of the words, the weevil-resisting adaptations
of the cotton plant would include only those characters which have
been increased by the selective influence of the boll weevil, but in the
broader practical sense we may treat as a weevil-resisting adaptation
any feature which tends to limit the destructiveness of the insect.

The adaptive nature of some of the characters of the Central
American varieties discussed in the present paper is reasonably obvi-
ous, but in other instances extended studies in developmental ‘biology
and primitive agriculture might be necessary to determine the origin
and development of a varietal characteristic which may have signifi-
cance in the weevil problem.

It is easy to understand that so injurious an insect as the boll weevil
has exerted a definite selective influence ever since its remote ances-
tors turned their attention to the cotton. Perhaps its earlier food
plants were completely exterminated. The nearest living relatives
of the cotton are the species of Hibiscus, Paritium, and Thespesia,
none of which is known to have any attractions for the weevil. It is
evident, too, that in the presence of the weevil the cotton plant would
have met long ago a like fate if it had not been able to take on its
various adaptive characters. That so many of the features by which
it differs from its nearest relatives have such obvious connection with
the weevil would certainly justify the belief that strong adaptive
influence had been at work, even if the other circumstances were
unknown.

In thinking of the relation between two organisms like the weevil
and the cotton we often fall into the error of too great humanizing,
so to speak; that is, we ascribe too great intelligence or too complete
a reaction to cause or conditions. Thus the weevil, although highly
specialized in some of its instincts, has, of course, no equivalent for
the human judgment. It will puncture, as already seen, buds much
too small to raise a larva, and will lay its eggs in the rind of the boll,
where the larvee can never develop. If the conditions are too favor-
able to the weevil. as in humid regions, it would undoubtedly exter-

, WEEVIL-RESISTING ADAPTATIONS OF COTTON.

minate its own host plant by permitting the cotton to produce no
seed. Paradoxical as it may at first seem, we may, nevertheless,
believe that the best conditions for the perpetuation of the weevil are
those which are not altogether favorable to its unlimited multi-
plication.

CONSCIOUS AND UNCONSCIOUS SELECTION.

There are two principal ways in which improved varieties of cotton
and other cultivated plants come into existence. The first is by sud-
den or abrupt changes, or sports; also called mutations, saltations.,
and discontinuous variations. These are represented in cotton by the
occasional appearance of a plant with brown lint,’ deeply divided
leaves” (okra cotton) or very short branches (cluster cotton). The
Guatemalan varieties represent a second type of evolutionary history,
in which improvement is accomplished by more gradual progressive
change, fostered and accelerated by selection.

Two forms of selection are commonly recognized, natural and arti-
ficial, the latter effected by man, the former by circumstances of the
environment. This distinction is of doubtful value in any case, and
quite obscures the important point in, the evolutionary history of
cotton and other plants domesticated by primitive man. It would
be much better to think of selection as either conscious or unconscious,
and between these two a very practicable difference exists. Conscious
selection implies the preservation of individuals having a desired
quality in the highest degree, while unconscious selection, whether
by man, animals, or inanimate conditions, means merely the rejec-
tion of the most unfit, so that the improvement of the species or
variety is gradual. Conscious selection acts, of course, much more

aIn Guatemala several tribes of Indians prefer brown cotton, and for certain
garments use brown cotton only. Separate plantings of brown cotton are not
made in the neighborhood of Secanquim, where our experiment was located, but
there were said to be such at Cajabon and Lanquin, only a few leagues away.
The Cajabon people have a dark-brown cotton called “ canch nok,” and a lighter
brown called “ canni nok.”

On the Pacific slope Mr. William R. Maxon found considerable culture of a
brown cotton called ‘“ ixcaco.” At Antigua a similar brown variety is said to
have been grown formerly in considerable quantities, the common name of
which is ‘ cuyuscate.” It was not learned that any special religious use or
significance is attached to brown cotton in Guatemala, as is said to be the case
in Peru and in India.

b Some may be inclined to interpret these as reversions and to argue that the
deeply divided involucral leaves may be a reminiscence of an ancestral charac-
ter of the cotton. Or it may be that the divisions attained by the involucral
leaves represent a tendency of specialization which the remainder of the leaves
sometimes share by mutation, in accordance with the principle of translocation
of characters recently formulated by Dr. R. G. Leavitt (Contrib. Ames Bot>
Lab. No. 8).

CONSCIOUS AND UNCONSCIOUS SELECTION. (al

speedily than unconscious, but is subject to the serious danger of
weakening its protégés by inbreeding, if the selection be too rigid and
persistent.

The unconscious selection by which the development of the pro-
tective characters of the Guatemalan types of cotton has been encour-
aged differs in no respect from the progress by which adaptive
evolution takes place in nature. The Indians have planted and har-
vested the crop, it is true, instead of the birds or other natural agents,
but they have been entirely unconscious of the struggle for existence
to which the cotton plant was being subjected by the presence of the
boll weevil. The Indians were only another factor, along with the
dry and moist climates, the keleps, and the turkeys. The problem
has been solved in a genuinely natural fashion, and affords an excel-
lent illustration of the nature of selective influence in evolution.

Instead of representing the final possibilities of improvement
in characters which vive protection against the boll weevil, the
Indian varieties of cotton may be looked upon rather as affording
materials which conscious selection can render still more valuable.
The proliferation character, for example, might never be brought to
uniform expression by unconscious selection, because the possession
of it would give the individual plant no advantage over its neighbors
in the production of seed. The proliferating plant might produce
no weevils itself, but the free movement of the insects would keep the
general average the same. Indeed, a plant might easily sacrifice all
its buds, set no fruit at all, and thus fail to perpetuate itself. Pro-
liferation can become a direct advantage to the individual plant only
under conscious selection. The full value of the newly ascertained
protective adaptations will not be known until they have had the
direct selective encouragement now commonly accorded to desirable
characters of other cultivated plants.

It may appear remarkable that such definite and potentially valu-
able characters as the weevil-resisting adaptations of the Kekchi cot-
ton should have remained so completely unrecognized hitherto. The
explanation of this doubtless les in the fact that cotton culture is
practiced in Central America largely by the Indians and very little
by the foreigners or the more intelligent part of the native community,
so that it had not received scientific study. Even the existence and
utility of the keleps, though apparently known to the Indians from
ancient times, had entirely escaped the attention of the European
residents of the country. That the Indians should have come to
recognize the keleps as beneficial and necessary to a full crop of cotton,
although not knowing that the weevils injure the cotton or that the
keleps eat the weevils, only shows in higher relhef the completely
unconscious character of the selection conducted in this system of
primitive agriculture. The Indians of Alta Vera Paz are extremely

(2 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

stolid, uncommunicative people, from whom little information is
likely to be obtained except as replies to direct questions. Familiar
from their earliest childhood with the agricultural lore of their own
tribe, it does not occur to them that these everyday incidents can be
of interest to the white stranger, or if they perceive his interest they
learned long since to fear it as a danger of further intrusion. Even
our own cotton experiments were misunderstood as a menace of addi-
tional demands for lands from the white men who now own so large
a part of the country.

SUMMARY OF ADAPTATIONS.

If the facts stated in the present report have been correctly observed
and interpreted, we must admit that the cotton plant is in a high
state of adaptive specialization in its relations with its now famous
insect enemy, the boll weevil. Indeed, it may be that the most dis-
tinctive and important characters of the plant, from both the botan-
ical and the agricultural standpoints—such as the involucre, the
nectaries, the oil glands, the large bolls, and the very lint itself—
are adaptive features which the selective influence of the weevil has
brought to their present degree of development.

CLASSIFICATION OF ADAPTATIONS.

The adaptations of the cotton plant might be summarized from
three different standpoints. A historical treatment would proceed
from the adaptations of the bolls to those of the buds. Breeding in
the buds, for instance, was evidently a later adaptation on the part
of the weevils which has called for a second set of the protective
characters on the part of the plant.

It may be better, however, to classify the adaptations as such,
without special regard to their historical sequence of derivation.
The more practical purposes are served by dividing the adaptations
into four groups: (1) Those calculated to avoid the weevils by gen-
eral habits of growth; (2) those which exclude the weevils, or at
least hinder their operations in the buds and bolls; (3) those which
attract insect enemies such as the weevil-eating kelep; (4) those
which prevent the development of the weevil larve, even after the
eggs have been laid.

ADAPTATIONS TO AVOID WEEVILS.

1. Determinate growth.

2. Early bearing.

3. Long basal branches.

4. Karly rejection of superfluous squares.

5. Seasonal bearing of perennial varieties.

6. Prompt bearing after cutting back.

7. Hairy stalks and leaf stems.

8. Pendent bolls.

9. Rapid growth of young bolls.

~I]
ao

SUMMARY OF ADAPTATIONS.

ADAPTATIONS TO EXCLUDE WEEVILS.

1. Involueral bracts grown together at base.

2. Closely appressed margins of involucral bracts.

3. Margins of involucral bracts strongly laciniate and hairy.
4. Unusual size and width of involucral bracts.

5. Calyx produced into slender hairy laciniz.

6. Persistent flowers.

7. Oil glands (7) of very young bolls.

8. Thick-walled bolls.

9. Tough linings of boll chambers.
ADAPTATIONS ATTRACTIVE TO THE KELEP.

1. Nectaries of leaves.

2. Large outer nectaries of involucre.
3. Large inner nectaries of involucre.
4. Bractlets subtending inner nectaries.
5. Continued secretion of nectar.

6. Hairy stalks and leaf stems.

7. Dwarf, compact habits of growth.

ADAPTATIONS TO PREVENT DEVELOPMENT OF WEEVIL LARV-E.

—_

Shedding of weevil-infested buds.

Proliferation of internal tissues of buds.

Proliferation from the walls of the bolls.

Absence of oil glands over dissepiments.

Growth of lint on seed.

Compacted seeds (Kidney cotton).

Lint confined to outer end of seed (San Lueas Sea Island cotton).

92 bo

Ou §

ns

ADAPTIVE CHARACTERS OF DIFFERENT TYPES OF COTTON.

The third standpoint for viewing the adaptive characters is that
of the different types of cotton. All varieties share, to some extent.
the older adaptive features, but the special characters are accentuated
in different degrees in the various types. Our study has been directed
toward the Kekchi variety, both on account of its relation to the
keleps and because it has seemed to possess by far the largest series
of adaptive features. But now that the existence of adaptations of
practical value has been ascertained it will be necessary to canvass
the field thoroughly.

ADAPTATIONS OF KEKCHI COTTON.

An enumeration of the adaptations of the Kekchi cotton is scarcely necessary,
because that variety has nearly the whole series and most of them in a more
accentuated form than the other types thus far studied. The few exceptions
are noted below. :

ADAPTATIONS OF RABINAL COTTON.

. Prompt bearing after cutting back.

. Very hairy stalks, leaf stems, and involucral bracts.
. Closely appressed margins of involucral bracts.

. Involucral bracts grown together at base.

whe

AN

74 WEEVIL-RESISTING ADAPTATIONS OF COTTON:

ADAPTATIONS OF PACHON COTTON,

1. Involucral bracts margined with stiff laciniw and bristles.
2. Calyx large, the divisions slender and hairy.

ADAPTATIONS OF SAN LUCAS SEA ISLAND COTTON.

1. Definite seasonal bearing.

2. Lint confined to outer half of seed.
5. Proliferation in buds.

4, Proliferation in bolls.

ADAPTATIONS OF KIDNEY COTTON,

1. Definite seasonal bearing.
2. Seeds compacted at center, covered with thick layer of lint.

ADAPTATIONS OF UPLAND COTTON.

1. Shedding of weevil-infested buds.

This is the only weevil-resisting character in which the Upland varieties
excel the Kekchi cotton, but, as already explained, the habit is of practical use
only in dry climates. The Upland cottons share, however, a large number otf
the adaptations, though in a less degree than in the Kekchi. Thus there is pro-
liferation both in buds and in bolls, the stems and petioles are somewhat hairy,
the habit of. growth is somewhat reduced from the tree-cotton stage, the nec-
taries are often large and active, the involucral bracts are sometimes well
tolded together, ete.

And now that the possibility of weevil resistance has been shown,
variations may be found in all probability among our United States
varieties which will enable weevil-resisting strains of the Upland
sorts to be developed. » At this stage of the inquiry it is too much to
hope that the Kekchi type will prove to be adapted to the wide
diversity of conditions to be found in the cotton .belt. Either the
Kekchi or the native cottons, or both, are likely to‘require extensive
modification before the full value of the weevil-resisting adaptations
can be realized. 7

CONCLUDING REMARKS.

The protection afforded by the weevil-resisting adaptations is
most effective at the two ends of the period of development, but con-
tinues in varying degrees from the young bud to the ripe boll. Under
favorable conditions an extremely small proportion of the weevil
eggs develop to maturity. Instead of a single attack being fatal to
a bud or boll, the same fruit at its different stages may resist numerous
punctures and egg-layings. The young bud is protected for a time
by the closed involucre. After the weevils have gained entrance the
first egg, and often the second or third, may be rendered harmless
through the proliferation of the bud in its younger stages. Pro-
liferation becomes less certain as the bud increases in size, but if egg
laying be delayed a few days too long the development of the larvee

CONCLUDING REMARKS. ras

is rendered impossible by the opening of the flower. Then ensues
another period of immunity while the withered flower remains in
place and while the bolls are still too small to be attacked. Between
about the quarter and the three-quarter size the bolls can still be
parasitized, though proliferation reduces the successful attempts to a
very small percentage. But after the lint has grown out, the lining
has hardened, and the walls have become thick, the boll is well-nigh
impregnable, though the surface may be roughened by a dozen or
a score of warts, which mark the location of as many persistent but
ineffectual attempts to gain entrance.

As an instance of adaptive specialization the cotton plant seems des-
tined to a very high rank. The development of such a series of pro-
tective characters can scarcely be explained except upon the suppo-
sition that the culture of cotton in Guatemala is extremely ancient,
and of this there are many other indications.

The practical utilization of these protective characters in the cotton
industry of the United States may require the solution of many pre-
liminary problems of acclimatization and adaptation, as well as of
physiology and cultural methods. The proliferation characters, for
example, appear to be much more pronounced in some varieties than
in others, but they are also affected, probably to a very considerable
extent, by conditions of climate or soil which check the growth of
the plant or cut down its water supply and thus reduce the normal
turgidity of the tissues.”

The weevil-resisting characters are much more highly developed in
the variety of cotton cultivated by the Kekchi Indians of eastern
Guatemala than in any other type yet known, and it produces also
large bolls and lint of good length and quality, so that it may be of
value in the United States. But even though the Kekchi cotton in
its present form should prove, for any reason, not to be adapted to
cultural conditions in the United States, it demonstrates, at least, the
fact that the Upland type of cotton is capable of assuming other
characters which will render it far better adapted to cultivation in
the presence of the boll weevil than the varieties hitherto grown in
the United States.

a@That the transfer to Texas will not destroy the proliferating habit of the
Kekchi cotton is shown by the following report from Mr. McLachlan:

“On the 23d of August Mr. Kinsler and I made a comparative examina-
tion of four varieties of cotton at Mackay, Tex., to determine the nature of
their proliferation. Rows of Kekchi cotton from Secanquim and Lanquin, and
two of native Upland varieties (Parker and King) were compared. The results,
in brief, are that in squares the Kekchi cotton proliferated much more readily
than did the native varieties. In the bolls all four varieties were about equally
active in this protective adaptation. The extent of proliferation in the Guate-
malan bolls was, if different in any way, somewhat greater than in the native
varieties.”

>

76 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

No end is in sight of the new problems and adjustments of cotton
culture occasioned by the invasion of the weevils, and no assurances
can be given in advance regarding the utility of the weevil-resisting
adaptations, any more than with the kelep, or so-called “ Guatemalan
ant.” Both have a present value, however, in proving that the weevil
is no invulnerable dragon which it is hopeless to resist. Instead of
having no enemies, as long supposed, the weevil is regularly preyed
upon by the active and efficient kelep. And instead of there being
no remedies which can be used against the weevil, it is now found
that the cotton plant itself has a whole series of weevil-resisting
characters—a whole boll weevil armory, as it were, from which we
may select and sharpen the weapons which prove best suited to our
purposes.

The weevil period of each year, that in which the damage is done,
extends from the time when the squares are large enough for egg
laying to the period when a full crop would normally be set. If the
value of the cotton crop be divided by the number of days of this
period, the result will show the value of each day of protection. It
has been estimated by Mr. W. D. Hunter that the boll weevil damaged
the cotton crop in 1904 to the extent of $20,000,000. It is therefore
a very conservative estimate that when the pest shall have spread
over the other cotton-growing States the damage will be well beyond
a million dollars a day for the growing season—in unfavorable years
probably two million dollars or more a day. Each day of protection
which can be secured by the utilization of weevil-resisting adapta-
tions will have, therefore, very definite and considerable value, so that
the study and perfection of this group of characters are sure to be
the objects not only of formal scientific study on the part of special-
ists but of general interest and consideration on the part of the prac-
tical cotton-growing public.

DESCRIPTION OF PLATES.

PLATE I. (Frontispiece.) Valley at Secanquim, Alta Vera Paz, Guatemala, the
scene of experiments with weevil-resisting cotton.

PuaTeE II. Fig. 1.—Mature plant of Kekchi cotton, to show small size and
determinate habits of growth, compact foliage, and long basal branches.
Fig. 2.—Plant shown in figure 1, opened to show numerous large bolls and
habit of fruiting on basal branches.

PLATE III. Involucres of Kekchi cotton, opened to show external and internal
nectaries, bracts, and bractlets. (Natural size.)

Puate LY. Fig. 1.—Involucres of Rabinal cotton, showing connate and closely
appressed involucral bracts. (Natural size.) Fig. 2.—Open involucres of
Kgyptian cotton. (Natural size.)

PLATE VY. Fig. 1.—Young buds of Kekchi cotton, showing numerous weevil punc-
tures. The buds were split in half so that the full number of punctures
could be seen. (Natural size.) Fig. 2.—Buds of Kekchi cotton (same as
fig. 1), showing successful proliferations. (Natural size.)

PuaTe VI. Large buds of Kekchi cotton, the distortion indicating proliferation.
(Natural size.)

PLATE VII. Weevil-infested bolls of Kekchi cotton, showing larger number of
punctures along the middle line of the carpel, where the oil glands are
absent. (Natural size.) ;

PLATE VIII. Carpels of Kekchi cotton, showing method of proliferation.
(Naturai size. ) ‘

PLATE IX. Fig. 1.—Kekchi cotton, successive stages of the boll. Fig. 2.—
Kekchi bolls (right); King bolls (left), to show comparative size. (Re-
duced to about one-half natural size.)

PLATE X. Fig. 1.—Rabinal cotton, showing foliage, connate bracts, and weevil-
infested bolls. (Reduced.) Fig. 2.—Bolls and seeds of Kidney cotton,
showing oil glands and protective arrangement of lint and _ seeds.
(Reduced. )

78

PLATE Il.

Bureau of Plant Industry, U. S. Dept. of Agriculture

Bul. 88

a

Tae ee

ee

Fig. 1.—MATURE PLANT OF KEKCHI COTTON. Fic. 2.—KEKCHI COTTON PLANT WITH BOLLS.

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE III.

INVOLUCRES OF KEKCHI COTTON, SHOWING NECTARIES AND BRACTLETS.

(Natural size.)

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE IV.

Fia. 1.—INVOLUCRES OF RABINAL COTTON, SHOWING CONNATE AND APPRESSED

MARGINS.

(Natural size.)

7

Fia. 2.—OPEN INVOLUCRES OF EGYPTIAN COTTON.

(Natural size.)

Bul. 88, Bureau of Plant Industry, U. S. Dept of Agriculture. PLATE V.

FIG. 1.—YOUNG BUDS OF KEKCHI CoT- Fia. 2.—BuDS OF KEKCHI COTTON
TON WITH WEEVIL PUNCTURES. WITH PROLIFERATION.

(Natural size.) (Natural size. )

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE VI.

al
LARGE BUDS OF KEKCHI COTTON WITH PROLIFERATION.

(Natural size.)

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE VII.

WEEVIL-INFESTED BOLLS OF KEKCHI COTTON.

(Natural size )

a 4 SA
Manin

yA.

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE VIII.

CARPELS OF KEKCHI COTTON, SHOWING PROLIFERATION.

(Natural size.)

PLATE IX,

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture.

ne

Fic. 1.—KEKCHI COTTON, SUCCESSIVE STAGES OF
THE BOLL.

(Reduced. )

Fig. 2.—KEKCH! COTTON BOLLS (RIGHT) COMPARED
WITH KING BOLLS (LEFT).

(Reduced. )

PLATE X.

Bul. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture.

Fic. 1.—RABINAL COTTON WITH BOLLS.

(Reduced. )

L

Fia. 2.—BOLLS AND SEEDS OF KIDNEY COTTON.

(Reduced. )

ble Oe, Ge

AAI CUMIMM AMINO OL SUUATES. <6 652 S602 65.225. oes. ese ete as-
Paola. SMO MeAPDOCIAUZARIOU! 222. 2-2 sec sei ccceh<- cn. e be eens a obs ecen eens
Pi cmAbiadhon ar mec GORbONs = 2222S oat ne isn s cee Sees see ee eee eee,
Accommodation, direct responses to external conditions...-....---...-----..
Eerie homie MIRCHSe Ms a ee ee oye oe ee toe es
Papluined Dy natural selectiome se 5-50-24 - en ee ib ee
PeLipiaiwons auiracuverto tie Kelep soos. 5-545 226 eee ne oe ee ee eee
Reece len MeOlare ete es ge en ee ee Pre ES Sea's cle LS
Glimahiaenteehaee tore eae een eee Bh ry NT oe ed 10,

COMMMRCT CLA Ey Altea te ae meres Pesan yeti etc eee es

(onbsjequeincell (REET nOaVET Oe) ss ee Re Seek Se ee eh eve eens

OCMIMIRSY MUNG OUTS 6a Se GER ee Ee Sees SESS cee eaaipee ne ets

Demons wien MOsemechVe <5 2 sol cece ntsc tess. ++ 3S ee

Gime Acts UT OxCOLLOUSr UMKMO Wala sae seme eae Ame hee i
INeEKChinanOenaOlMaCOtLONS's seen saeco eee see

Kidney, Pachon, San Lucas Sea Island, and Upland cottons - -

SCOEPELUTE A Pat tary ee ce pd Me a a ts bea Oe

LO: aiVOId Wee VIS) se nee eee Sent HOe Sa B See Bee ee

ERC OMMGLEN RESUS) 2s Sars Same Meee Oe AED DO eee eee eas

prevent development of weevil larve .......----.-----------

OO UIVeTC MAPACLELS: CXte Mts imei er acwe = Save eat ee ee SO Se
OUD Ieee ere aera Sar ye ee oa eer else, ote tore 2 is SPS a

EOE COLON CH ATACLCT Garey Manns emesis aaphete sy Be Leia) het Ort
Aeneouonmearlien than Minoan Guatemalaoe-22-.- Sse. sass se lek oe
Anthonomus, behavior of species related to boll weevil..-...-.---.-------.---
ANTIPGI DUAR TIMNQO NOMS. o He Sees Se BOBO SSIS SESS Ieee ee ee ieee aa
Antigua, Guatemala, culture of brown cotton.-..-......-..----------.-------
LTS FE AUS EUA ef CLE Ci RII G(R ata ROAR ee pn at ale
“CUTARAYTUUEM RWC O88 20a Rael A SR ee aR 2 eof a een a a ee
POROLCCEO MIP eINGG WEEVIIG. 2252-2 nal y tox o-te sete oc ee ood ee

cE EVSNG OVEN CEST PUTT Cn ON A te 0s Sada a i ep
ANTALIS TEATRO 80) (CONIO NO g PaO oe ee Goon So See ee eee nner re
Aphis gossypii, infesting plants at Rabinal, Guatemala .........-------.-----
Arid climate, inactive nectaries an BGautive (RESON, Sere ey yen: ele A ie eee

LESIONS se avlOrOtmCOLONM eats meer Mee S'S es 45, 4

type of plant adapted eS ee re oe ah Se Reg AOE Set
AmiidciMeselecton amuncaehmitetenme: sae=see sees) 8 ee a ee
shined armaWalliamubel antsimdentitedea=== sere ys ee lie Lae ele
Asiatic cottons, comparison with other varieties ........-....---------------
jAYEVOEVRKBSE A ek ets Oe sire ee pee age nee tere

Bacterial diseases following weevil injuries........--..----------.----------
BIG CHS DU GSO Ene CLAba LO CN Cedeme re eens ee ati Bets Sek eS wos es
ipiios .waliie ase weevildestroyers\--- co. o- 2-5 <2 2 nose et e S
Boll weevil larvze, adaptations to prevent Be lgpment pee ey Ske Soka 52890
behavior intGuatemala and Texas .......0 5 2229.4262-) yee

destruction by drying out.of squares...-.......------- :

ROOST LLO ie cs 5852) Sp Soe es ke

development inn pols 2:73 56 a 6s oh eet ees. wee

enechiorapomme Of flowers. 2.522.222 0.0 2h ieee ewes

rapid development in) PUGS 2425-22222 oko ecto es ie

weevils, absence from Eastern Hemisphere ---..-..-...----------------
Wexican, plateau repion . 7257. Sake. 2S a. ose

AGA LAMONS OM VOl dee tae slr) oeceel ote otartera eels fae = ere

XCM Game seme eee bea eee es ae

DC CORCTOSSALC TUN Zt] OMe see oe are eye ete rein yas fet ee er

80 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

Boll weevils—Continued. Page.
bacteria] diseases following injuries: : -. .22.1 52.022 220 eee ee 62
behavior in absence of keleps. -.. 22.- 222.2. +-d22fi< 2. sees 24

on touts <2... 3 te te ooo ees ae oe es 25

within bolls... Fos... 2ses sek ac se eh ace ee e 59

best conditions for perpetuation .....--:..-.-.:--2.--2--25-2-e- 70
change obhabits: 2.755. 322 pare cout A ee coe ee 63
destruction by chickens‘and turkeys .-...2..2--.-...22 2.40208 24
determination of life cycle in bolls and squares -...........---- > 64
develcpment of pollen-eating habit -..:-....-.2.-2.-4.-22.--2- 63
diverse habits of males and females - ---.-- cig a Seae aoe eee 27
diversity Ini size 2225 228 = seo a GEE eo eho ae ee 64

effect: on unprotected.cottonfield 022-7 =. 283 eee ee 35

under favorable conditions: ? (42232 ee ee 69

Caps, fabe fo Neo. oo Sees ie ome oie ne eee 58
exclusionfirom large bollsi se oe ase ore ee ae 59
feeding an-bolls 2 72 3 eee Te eae eae aes Sees a ee 61
general effect on cotton plants: 222422 oe ee ee ee eee 10

in elds eultivated Ty Indian: 9°60 5- S22. 2 oe eee 35
injliries an anatemala 255750 See ee ee ee 47
injurious nature unknown to Indians. 2. 23:-0 se 71

. mortality amiqprimng: 05 eo Ue see ee ee eee 14
not attracted by nearest relatives of cotton............-....-..- 69

pollen diptnye 2229.28 a ace ie eee ek eo ee 58
preference for upper portion of plant....................-..... 27
selective Innes 2 -o2 32 Soe nae ee ee ee eee ee ee 10
self-destriction S202 es. Soe de = eae Geran Seen. Senne mapas 34
short-season varieties of cotton for control ..............-..-..-- 22
StaPvaliOd 225 2b ook so. Sao ae ee See ee 12, 14

Bolis, diseases from superfltous nectar. 232 Seo ee ee eee 28
efficiency of adaptive characteris. 322 2-- Sok ee ee 61
fed upon by boll weevils: -- 2. -22--5.- 3 bla) a arcle ae a = roca 61
feeding punctures s2500. 7222252 noah Se a eR A Se a 61
infestation by weevils o<....°- SS 29222 feces oe ae See eee 50
injured; discoloration’ 2=. Sse ec Sao Saye een ree 56, 59, 62
Kekehbi cotton sdesenip tions: 52s ane ks eee 16
IMMMAihy =< acs Sn eer eae 56

linings of chambers, toughness as protection from boll weevil - -------- 56
normal “absencevat Rabinal’-Guatemalaa soso) se eee eee eee 24
ollglantises <i cott oes cae Bo Re Se ee ees Se ee ee ee 53
outer walls, proliferation. ---. ey Sige he eee ences Sea eR ta LM So oi 58
WANIstion In thickness. ot. © 3.2. S ee ee ee 56

pendent, discussion se sebck soon e toe oe ae oo ee ee ee eee 27
periods Gi amimunitys 9.22 3554 Se ee eS hice nyo a ere ns Sears ar 74, 75
POSLIZON oe ee tee apg es re th ee nae aoe ae eee ee ee 27
proliferation casio F rs Se Te ees ee Se ee eee ee 59
ii relation: to that of buds: 55-22 222 Po oon eo ee 64

PTOUGCHON 3 8 oocs. CoS Ste sek Viren sea ee Mace Ne ae ee 51
unconscious selection for uniform ripening .......-------------------- 11
very young, Immunity. 202200 oes ee oe ee eee 52
weevil punctures -......-- SI Nie ae cae trae eee ery, Dien eer tol pa cia: Ale ote 61
weeyil-proof lining ..-....---- SS wide wg elena el a ete ate ieee ne 57
young, rapid growths: <2 27 obs 0 ue Ge eee 2 eee neue ieee 5d

Bractlets' of invelucre s Loe oe ees alse eee oa ee one ae aes eee 33

Bracts, appreseed: Marine !> = 232.22 fees SS 2, ee ee ae eer ae 38

dimen#tons: 22.2250 - see sce eee ie ee ere ae ae 40
Haris Sos 5 at Se RO ee Ee EEE tc 40
inyoltieral, srows ‘tdeethor.= =.2 aco! ole Re ieee se oe 37
harry Wiking <>. 52t5/ soe ee eee a Ea ees 41

lacie oS oe 28 Fon eee eee | ie 45

of KRekch® cothom:. 22 i222 6 cent Se ee Sa ee 16
protective feavire of larve:size «2uc_ of 992682. oes Ns oe 39
Branclies,. long basal, disadvantages ofo2. &. 4252 sve2Se oie tea 20
ob Kekchiveotton + 8 s45 Ces ee ee 19

of cotton, compared with those of other plants..........--------- 19
dimorphi¢e <22552 > fed i te eee 19

INDEX. 81
Page

Prewri,COLbon,, OFiP I ean =i-tr ~~ => = 12 fae eee Se Soa ads ees 70

puctcretice im Mimianie) 2.22.2 220 3 - annonce e+ -2--=- 70

oT TERE My Piss rc ee See ene ee eee nen 52

nnd; breedimenn, 4 Gerived MaMb. 25-22. -- = --\----+-2+ +228 es sees sss. 62

ibn ieee weNl COLON: 2-2 s-2-2---- 2 --=-)-------~ << oe ae see ~ see a 20

Have: loai ais, LS So a ee 40

SEG a0 PQ eC ee oe a ee es 21

PyeeOlemekede WeeVviles. 2.2.22 .--<-252--~5-.--2552-5----2-- : 48

fifhe Siivcoly fect) i ee 43

PemoonalmaMUMNy 5 9 92--- 5 sas =~ sco 1-2. = ess - +--+ ---- 74, 75

persistence of injured -..-.-,--+----.------------+---------------+--- 47

prerelease See as ons Sapir fase - a Sew sees eee 46

CAUCE SAN GU CONGILONSe Mase = eee as ceca eee os 49

MOELC LATO NECOMM At Ol OOURieet Sansa ose siecle ccc neta ke 64

protection by involucre’. 92 --o 2.2 oa 22 see oc 2s sees = es eee 39, 41

recovery from weevil punctures. -...:..-------------- SUS ele ee pase 41

MIDETUGU ES = fo Sane ease eed aid in emer ne fo = fa are ae soe ee 21

Mette mite eee mene eer Pee ta eee ne ios ae ona 22

(Mem sstryel sievsolehic Cues ae ee ee 74

Cacao branches compared with cotton ...-..:----.------------------------- 19

Cajabon, Guatemala, cotton grown in vicinity .----..----------------------- 15

pannus er brown cotton: 252522. - << 422-2. ---+--+--- 70

Cecropia, symbiotic specialization......-...----.---------------+------------ 29

Grirkeus bolleweevildestroyers=- =.= .< 20222-55252. 25222256. 522-2542-'--- 24

inmate, ekect of change on Upland varieties. ....-.-:. ----+-+ -i+-+--+-+----- 16

on earliness. 4.225626 i OO a ed a Sta eee 7

SArMUnAuourver seed = f=... setae os ets ee ee 2 15

Climatic conditions, effect on United States varieties...........------/.----- Uy

Siieuin mana plaiOUss: -2-2 9.2.2 2-2 Se < oe aes weet ote eos See 10, 48, 44

ROMA MeO Oliee mck iano ct eee Soe Oo Lee Mos oe eee ee ily)

nisi icmho MISO LORIOEE 4-2 ..2- 2526 so el ao ek sends fe We Shee Rete ees. 28

Dio Mee en areek Sueintoah..cuehasou ee eee eee ee soe 70

(GPELLYES a1 Pl 6°5 =) CS SS ee re Ree enn eae ay eee 28

ea eel ONIN CH PGI ootery = Dd Sp lo lee eee tia tee m eeins = oes 21

arise WMC GTO es ma ee Hac een ieee sine ae a fea 17

Woitee ranches compared: with CObOn .!- 22.25.25. -2Gs- sce 5-25. -e ose enn-s 19

Call vemRonomeuaplerl VAtICHeS .. 2 cjcc 2 onan a ocean ce etin wena LSet ves -- 18

TiTCRTEN USE = te al ie OS I Sm ed Ca ae ees et ee Ae oa ez anlis

epitnnere te Ne MOREE VION S500 2 A ba aki th imine wis win Sennen esses 54

(CiatiselOUNISe Le CiLO Ni a pee Sie aa eee ere = ye ae sce e sacle See Sea seins 70

Corn, effect of changed conditions....- --.-- nn ee See at ae ens 18

UG ETN Te ances Aa SUT (C06 0 10 IS oR ea 39

Production. pravamie Gx temsiON 2. - 2.2. -----s-24-5-05----+-5-- 44

SVOnt-scasOumyalll Ghleneree merece foo eae eee = maison ec =.o tins 12, 14, 22

SMU SuOleMe WE CUNGNIONS 22-2252 = nese. 5252 totais cee esc eemeosoes 17

@ross-fertilizationsarded by boll weevils: .....:-:-..-----.--+--------<----- 59

elec onamultaneous blossoming. ---.-2.5-.-.5-.-.-+=---- 23

SP emo meinmoe nN MECtAn: Sos <.n/ 2 oe eta emi = ss oe ee ee 29

Sbiaiy panict Wor cat Ont toe eet ee Bee Soe eo on ee nee eee 23

Culture of cotton, methods, in eastern Guatemala........-.----.------------ 19

on Pacihie slope of Guatemala. 2-2-2. ..-542- sac 7

Ii esxd COM tener e See NS cine eee et Cee ee Boe ee 45

Determinate growth, of Kekchi cotton... --.--..2 2 ~-0-a-20e eccinse se seeee se 1

habit, disadvantages of early planting avoided._........-------- 14

PrintirVveMeAnGWes, aMaRtOn =i. on ok alae acincie = 20

Dimorphic branches. ---.-.- - - Fe Seat Se eee Si FOr as an an 19
Dry climate, region, etc. See Arid.

Dwanicorton.-cucc, on cultural methods:.. .....~.-----<--200s--b=-522528 5% 19

[Peet h Giles Qe el TES O07n 100 eee ea pe, ea ete aero 11

Earliness, effect of development of primary branches ......----------------- oe)

GAA EL CRC OTC OMS eee ae een ete ee eto ees Syts eae IPP NY;

Rossow icy Care OLnowernes- 7 8! s- oeaeeses cers qeis'ee Bia 13

Early bearing, facilitated by long basal branches. .-....-.--.------+---------- 19

planting, disadvantages = iis acc. sacle eo neem ee nw ee nce cee nn cena ne 14

9962—No. 88—05 mM

82 WEEVIL-RESISTING ADAPTATIONS

OF COTTON.

Page.

Harly. planting, discussion }. s22- 2022p es pee ee cate oe tree aera dee 13

essential in sdutherm Texas. .i22 5525-4 dese ese eee 12

Egg puncture sealed by ‘weevil 222.2252... .:0-. 25-255 -. 425 ee ee 61

Kees of boll weevils, encystation’....-.2- 2325) jd ad Se oe 58, 61

Egyptian cottons, immunity from-bollworm..--. .. 7.2... 2282.5 alee 53

Involucral ‘bracts. .2 > .- fac was 25 522 ee ee 37

less hairy than Upland varieties... .—-_ sv. 25. = 5 eee 25

not immuneto; boll weevils. 45-22 tL eee cee 42

oilplanda: 22 5s oe oe ee 53

of American origi: <0 2. oc 2h el eee 9

precocious'in Guatemala: 2. oS ee ee 17

preferencé of weevils: 6°27 (2 i eae 8S sae 26

proliferation: ceed see eek een see eee 50

susceptibilijy to itjury cok =. <2.nee a2 25-2 Se oe ee 42

Environment not actuating cause of evolutionary change..............------ 68
Eyolution, illustration of influence of natural selection: © 0.1 0Ust a ee pee il

bo) volutionary onein of exterial-mectaries....s2. 85.) = 2 eee ee eee eae ol

Hertilizationy discussione ss 28 2S oe PS Tae Sere Se eee 52

prevention Dy Tain: 2222535235 Aa eee 21

Field cultures, failure in plateau region of Guatemala Sota Settage neyo eee eee 25

Flower bud, posiien-ra ee oe ene ect eke aut es ence eee 20

Flowering period, SHON a Aa Se 4 ae eee hee a ae Skt e ae ee ee 23

Flowers, foilureisi pellimation® 2... 22053 oc ye cated ee ad 51

Ire le pa ummpriscipe tte eee Sans She den set oe ee 29

of Kekchitcottonicolors 32,5.c. oe Se see eee ee 54

Kidneyiectiony color. 43 2.326.555 ose eee 53

opening, -etlect onilarvas fe 2 so a ee 47,63

persistence: .jc.:<7 7-2 eds oe ees rods ee see See eee 51

POSIMOM Syke re fh Se arts hee weg Ce ee ae 20

Foliage, compact,vettection/keleps Uai-< 505.2 on eee eee 26

Food, change, advantage to plants and animals: -...... = .-62.. 25.22.55 ee 26

Fungi, grow bliin meetnien:. = = 0 2506s eke Seabee as ae eee 30

Germination, coltom seed in Guatemala: >>) 2.5228) ees ee eee 15

Gossypium barbadense, ORI S215 252 bs ccc eias 2 Sc cee Sok ee See 8

herbaceum, Asia Minor vaneties 222-332. 5 ae eee 53

coniision with: Gohivsutunt. 552 2 ok OOS See ee 4.

MOChANIGH «osc fe 2a SoS a 2 ee a 31

perumanum, epecitie validity 2 -~ 2582 (<2 302 2-2 aaee cee menos 67

Growth, alternating periods in tropical plants................-.-..2-------- 23

ulthey ol accolenition: 64 220522 ls ee oes: ee eee ee ae eee 5d

Guatemala, central plateancc.. 2 ste on SoSce clk ee oe ree ec eee eee 24

easter, climate sie. 2% so ee et es Fo Aes Ee

metiods-or cotton cultures. 22-05. 20a eee eee 19, 70

Nature Gh the country 2s22 52 555 (SS ace 15

heldiex periments. “222027 at Le hs eS eee 34

laiportaidon: Ok foreton GHIPAGl. ese ae ses oe ee a ee 24

indian: methods of cultivation 5252 2220-0. een ee ee 12

Western, \COLLOM! 22 <8 SeRE Ce 2S aoe se eee ee ee ee 25, 70

Guatemalan conditions, effect on United States varieties ..............--.--- 17

cottons, preference GEKCE DS. fan ce ce ee ee ee eee 25

Hairs; cotton plant) assistance:to keleps-o25.5— <<. 20. -< 2 Seater eee eee 25

Hairy Guatenialanivarieties ol ‘cottonecs. Ji. so See ee eee 25

Stalkeiand leaf stems.of cotton. <<) 7s eee ee: Ree 25

Heredity mech antigmt< ee ots 28 Pe AE ines ee eee eee eee ee 68

Hibiscus, involucral appendages’ of species -. ~~... - 22. -- = - <n - - - nem se 33

mectarics Of epecied? 2s 2 <h ae, eee eee en ee ee 32

species notatiractrve to bell weevilos- ites. 22]. so eee 69

inds: Wir Hes ODSEnyV abo NG ete. net ee ere ee ee eee 25, 42, 43, 44, 55, 61, 62, 64

Howard, Ol sobsenvations an on eee eee he Ei ee ee ere 45

Humididistricts,; behavior oficotions-- casa eee soe aeeee see oer eee 43, 44

Elunter We Ds, Obsenvyahlonstes see oe ee eee 14, 25, 2 , 43, 44, 48, 55, 61, 64, 76

Immunity of budsand bolls, periods 28-0 oe 74, 75

Inbreeding of cotton by Indians. 25.227)! eee 15

Indeterminate varieties unsuited to early destruction of plants...........---- 13

INDEX. 83

Page.
nGuanemethods Om conOmculbure aes see seeee as secs eeee comes Comes eee Sack 11, 35
TMATAE SO TOO DLO Meter teeta cee a ee one nats Oe tro ka 53, 70
lian aciculturalshaloitdeace: sccce cea: se ses- Sai Seo eee Se 11, 15, 35, 48
EOWA COUNT, OND UI DN a 9h St ai ee Oa ed ee a 1135, el
CHIGIVEOH Oly PEPPOlS coe tote onde Ses ethics Se csce nes Bseene ua nece ws 11
CuUStOMas isk AON eo MALeM a Bee eae oe Lees Se ee SP 24
FORMAL OTOL MEW mVAeULON gee eee emetic on. oe ee ee eerie . Shes 15,71
Guatemalan, observationsion boll weevils. -.-.=2.22.2.-+.22-.--:-.- 66
ot Alta Vera Paz, Guatemala, characteristics. ..........--.-.-.--<--. TALE GY.
BOLE GILOL SN dO1gCOULOD Meee ere Reh Ir tata SL Se 15, 16, 71
ZA ONOMCOLLO ME mney cae ome er ese eiate me eeale ee nites we oe 45
ImnterbreedimoasmecessarystOnviG@ON.c. o/oece ass f= Coes see cem eet os Seetcdac cess 68
Involucral appendages of plants related to cotton ..........--------.-------- 33
bea eis lee aAChOMIGOlbOMemen errs Seca ee ate ee Se mee cee seicc se Seis 25
imivolwerewas asprotectlve Structure’... 2.2 ccc see Sacl ce cook ee fee en See cee oT
[SERVE NEMA Se ES es PA ey ON ee et ee kg 33
SRiernalnectavles aCuscUsslOli se See ok ee Seem gee eee eee 31

MINE TMECtANLEE WGISCUASIOMe see mmcee so gaye See ee ee cee case. 3
Protechion. to INside NECIATIES».o< 624i Sentero seasen ce weiss 28
EOlectivenvalitercee sac: emer ee eeeemer omts ined acinseeiecece coc 37
lireswalpre gers raVostelo eve Weiner) St ye = ee ee ee none aaa 38, 41
LI ORVO WTI COMLON Seseteepee aeteer a Riot aera sae Secae Ses acc 25 Se 41
IE Ke hike Ohlomeeense acer, se eae ceo sees eee teeiat so iion oa. a2 37, 39, 40
LSTOLOGW? COMMONS Spee SSE ory ee i ae EE eee er ee 32
CEU AC TAMAS eee eee Sere eee ee ume sere ot Mk tS le 42
alte COMO ME Se Ce ete = ee ee ee Sect eet 1 ae toe Sy
Searlsland cotton, attractive to! keleps-2.-= 22) -52.-<--2-<-25---- 26
hlandico bons tae ota emcee nee ie peer ere a sie e em 38
WAGE ROCCHI Shee oe oo ee et A hieetn Suits oto ones ae 39, 41
Gite H AMO ATONE TOSS ps ret cls (eam atte ere ete eee SRM SI ee te le a 45
ICA CONCOLLOM ms GUAbEINAlA pam ee nme = ee een ce anime cen a eae clot sn 3 7
Jannovireh cotton compared with Allen: -- 1-2... sceu nesses secs se cee ae ily
POEOUITG TAU GM Serer rors ee soe, 1 ae cic iis Roles Moo ek 50
ewe ttnconons Cimensionsom buds ala) Dracts==s5+-26- eco. cceeeen eoeeeess< os 40
PfCKCIMRCGLON: aapiauiGhs 20.4... tect Nee sao. 2 eee cokes wel te
ALOR ero Mob. Or COtOnsCHI Gre soe) oe ene aa ao ee 18
JoSlovanyiroyewabayd Neb tris eae ee ys eet ER oe a eee ee 7
Dolls avariahionwneamickness OF walls=]-28sesesee se ha: 5 Stk 56
Charactenistleieatunesase cee sco ae eee aes ae oP Soe 20
comparison with other varieties, at Lanham, Md .......--.--- 18
datcwotsplanting ineGuatemalan sve see- sees seat e esses ses 15
developed in weevil-infested regions ........-.---.----------- 4
CIShMCtiby PElOl G.ossypiINy NINSUUUNY = 2 2a ea- Sess es ase 8
elect oircrowdine on eharacter:. 2 5-.- 25sec Sade seca s 20
AUIS Vs eh sec Ae oe tae dS ae ea 2 a ee ee eee Snes Oo GON eee ee Wy
HAND teatOle Ono wit lar eee ee Ae eee a eee eee eae seein 15
rel Waves Uirawtl XC MS Nese eee eset Seren en Bel oe ae aN a reese 17
most promisino short-seasom variety 0.---.-:-2=-.:---<-<--s- 22
Gunellluitayen Oleg LUI Gye ees ra eee ye aco e Saeee 7
Ton Ment Cok Koyayanee a6 ae Ae aaa sos Sane eae te ctene ae 55
Shioniness om season exp lamanlOne == 28s ese cleee seco eaee 11
Stems spevolesmleaviesmangdebOlls =. oe. soem ee sos ceee sane 16
LOLET al GeKO GO Glare mee ree ses es Sinaloa Anya ees aisle cfs eiqsieae 15
RICHI SB BERS AE SCS este ee ec ee a erie 15
WECM resistance. mie h) Vallee ese ee ne oho oc a cesar 11
Keleps, absent irom Mastern Hemisphere 2-2... 22 ...- =. --2-ceee 5-5 32
EVO OURAN TWGVOS | UNUM NN (eyes SE ee Bees ee ar Seen Aer eee a Se 73
detinitely:ahimactederoncottommeplanits a neem <sree ene enone 35
Pier Che Tinto MAB Dt ene en ets Sareea antares me ae aoe as 26

VAS Uhethee SLC TSE Mpeerne Ate ste nin ey era ete Le eS De 3
has OMcotioneplanbhy assistance in Glimibine + = 22-2242 e5 44625 -- 25
AMAR OMT StS Ml MO WeI se kee eae Cee = Secs Soiree eerata renee Sia wine has 29
preference for Egyptian and Sea Island cotton and Bidens pilosa. . 26,36, 37
LOLECIOM MOL COULOMie ees ee ere ee se Ce oo kame ie alee te cee a a 8, 34, 35
unknown to European residents in Guatemala .........-...----.---- ral

84 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

Page
Keleps, usefulness in comparison with ants..........---5---.-----+--------- 39
value, known by dndians 22-3 225.- Sere oe se 71
visitation of other nectar-bearing plants than cotton.........-..----- 36
Kidney ‘cotton, adaptations 27220. . 2.23. ba LE ce men see eee eee 74
at Trece Aguas;:Guatemala S222. 22 23 sake eee eee 32, 53
Ticur, Guatemala. 2222 2 See ee tse ee a ee 24, 66
charactersi:2.2 eee a5 Sa eee aa eee 67
Cultural vale os 2 2s ae Sas ee eee ae eee 67
of American originsscii oi ades coset ek ae eee eee 9
Ollelandsh. ute Be ee ees Soe oe ere 53, 54
Origin OL NAMES. 24. Sashes che eee eee eee 9
protective tieaturesix: A225. 2 8 tse eer ene aoe ee 42
seed arrangementiz< 22.2 Ue aha eee See eee 66
thin-outer; wall otsboll 22. 225 as ees So Se ee 66
King cotton, behavior in Guatemala. 266-22. es eo ae ee ee Uy,
cluster variety. olor =< 22 oe so Se e ea eee ee ei ae Wee
dimensionsiof budsiamasbractsa2essers. 46 ee eee eee eee 40
fanino Ol Sqmares: so. ws sce pact soe ea 2 ee ee ee 40)
Jan SesHeClaes:.cc:<,o:o. oe o Be EO ee ee ee eee 31
DrOUMerah Oni. 8. Ss os. usec Sa eon ane aie eAncytt eieerane 60
rapidity ol development =... 22 = S.A ee eee eee 55
Kainslen cbs sO DsergaitOns ams Soe eee ae pe re 17, 29, 37, 47, 50, 51, 55
plantecultiyated im Guatemala +250 5.2:-.- Sl aS See 15
Lacinise ofanivolieral arate saree eee ots ie eee ee ye Seren) 43
Lanham, Md. experiments sos te aera cere ee ee en ee 18, 25, 48
Languim, Guatemala, planting of brown. cotton... 22-22-2222) ae eee 70
Large. varieties; disad vantages 923.0. sess aces Geet oe oe eee ee 19
Late planting in morthem localities. 22. 222.25b. sss G 5 ee ee ee 13
Léaves, “Krele¢ht.. cotton 2+ se ee ee cet oc ee be a ne oe 16
nectaries: cen eral iscusslOnaise5-— cae aa. Shoe eee eae eee eee 30
Keavitt; Rk. Ge, principlevot- translocationiol charactersie-- 455-2 eee eee 70
Taimbléss variety: of Kone, cottons... ee enor ep eee eee ane a ee 17
Jhint disad vantaresers2 8 soso neccese e errie vaer eeate ete atone ee 65
protection Ol: seeds 5.0.8 tee ne ue Seek coe oak oo See eases ee 65, 66
hocke* numberin Wek chilvcoutome -- ose = ee ace cee ee eee ae eee 16
Mackay,.Tex., examination.or cotton: s:..2 ate. aoe oo ee ee eee 75
Maxon, OW.ch,;cottones ptaimed ia oe ee Se ee ee ee 25
Observationss--eeeeee oe Bape SET Se ay ew gt Oe a en een 70
Mekachlan,“Arovle observations: =sosesss2 ose ees sae ae 18, 25, 41, 47, 57, 60, 61, 75
Melanthera deliowdea visited: by. keleps..22no22. 3 ce son 22 oe Dae eee eee 37
Mexican’ plateau, absence of weevils::..-6ssot2 2. se ee esse eee 11
resion, Advantages S325 32 JSP aes 5S. Sa oe eee 45
Mexico; cotton. culitittrey-caae fa, tee 2 Sate a eee oe See eee eee 45
Mit Afifiveotton. ol clands* 3205s ee se eee Se ee eee 53
Molds: erowiham: nectaries 22222555 os 3 ee eee oe ee ee Ee ee 30
Moquiindiany cotton characters: —.-ee ee neoae ose eet eee ee 52
Mutations intKekchi cottomic: 3 3ascse Sane secre eee nee eee See eee eee 16
Natural'selection by boll weevils 2. <2 ock anne cain co tnee's oe a eee 54, 69
COULOM! “Sao Nice ee eee aa oe ne SEE eee aie ee 9

CONSCIOUS ANG-NN CONSCIOUS --— =e eee ee eee 7
effect of oil glands. csocs = a.3e joc eee ee eee 54

illustration of influence in evolution ......---------------- 71
in’ simultaneous Howertg 2... 22 co- eee ss <= eee 23
not actuating cause of evolutionary change ......-.-.------ 68
the explanation oradaptablOneiae a —se eases oe eee 68
Nectar, continued secretion) by, plantss2 3. -ceesee se eee eae eee 32
PUT POSE = 3622! ABU ee So SOS ee eee ae pat PIR Bio ete oh a 2 28
secretionim Kekehi and Wpland) cottons=25.2--2--¢- =. 22> == eee 32
On Doll Seal se es oe ces Pe te eRe AES eee He is. Se 33
Nectaries,:extern all 1discuesiones a. heacs sro tare ee cis ee 31
position an pendent bolle... 2222s. 6-2 esa eee eee 27
REGCKEUM OMe ee Micke AR I ee ern ci 2 oye fae 27
extrafloral, connection with bacterial diseases ...------------:---- 62
Giseussione 2 ese Snare a Oe se See ee eee 28

fUNCHIONS Se oe eee eS paisa ene aye Se a da 29

th Se

INDEX. 85

Page,
Metianies. ExXtraloral, MUMekChd COWOU so Sue. se56- ances o-- se cess ee ess 34
floral, no connection with weevil resistance ..........-..-..---- as 29
OTN O LOD Vee nes ee ae me an ae Nena Seen Me ene eee be tod 32
INACHVE Olek Oa NCOOME ar 4 a= ses a8 wees ae oe eee ce cle eee ae 24
inner, bractlets subtending ............-> Spee lor eee ip a ha ieee te 33
connected: withidroopime habit. 222... 0.222222. 22-22. 28
Ole MVOMIGL Ss CUS CUS OMe mae meee ae eg ee eee es 31
Oimcinerent sarees semen eee ket ee A Ne eee eee re Ble ade
SGI COULO Mera saps eee ere ie See cre ae se cee eee 16

IPAVEs, SSUGEAL GiSCUMNOM eo ccms. 2k. some ene dees ane ao 3
SCE ib Ce ea RS ree eg al eas oleae nse wletcee a Ss 32
Gil GUE TARO USS (ext Vote) EY SS ete es aia Rican rh re AE CR ae pie ee ee ee 53
IeePeCeMene nNOS toa cs See eee ec ane eeu ee Se Se esas eee cke, Day Oe
ON ea COMIOTA, ACIENETT AIS? ee a meet aR ee SERGE Ae A el ee ee eee eae es Cee 70

Old World cottons. See Asiatic.

MreiiMaconPOue an ATIC LEMONS Aso 2. aon n sade cee aeeeee enc ene e det dese 21
munpLoved varieties ME COON. |. 22 eos tees Chote Set Sect 70
Ei plane aneuied Gh. COMO Jet Haare a meman tates te SSE Sl ewes oe 10, 44
Pepe ern COLOME a eons oe ern a ete ae ome nome ecnsésse5 se 74
CL OTEKG Reins toes SE A le SOO SO ea eer 34, 43
comparison in Slexnsiand Maryland... .-....-...-2..-...2-- 18
. HOSUETIEES Goad 52 ee Re oe Ca oe eS ee eee 25
SRT MENA tans oo en oe nig tael atic “Rimes ec nes owes 25
Ealner Ur Bgward, discovery of weevil /.- 22.22... 25 .-- 2. ecee eee 45
OMSL VALONS. OMe COUOM\ ess fees Somes a na ace 2 45
Paeereen elects, Om DGlL weevils 2525. 2222 se Sec nace enn S hea n cee cane ene ance 14
Paritium, species not attractive to boll weevil ..........-..-....-.----.--... 69
Patwen COLON, GImensions Of DUdsiand bracts 5. caso. enn -nk--- aon e ene 40
SEMIN CIA Ua ee MOON Wty ee oe cia an ow cic cue 2 cate 41, 57, 60
CAST OOO Ree eee a ee sina a tem dint Sigerdic nee 40
[OER OS i ag PPI VG gh otetee = SS a a a Ca, ee 60
RendenitapollsncisCusclOlleretieee eee ich ks sere eemeiwr aa. 2r U eRe ges Sie 20 Ws Dit
Pepe in portance to IMOINS se cose oe kek Soucek Sle es 11
Perennia comons, annual cutting back, 22. ..554.2. 52082022256 fete ek 24
not likely to be of use in the United States..............- 67
‘SYeeev stay avail aye ah aVeae Ce ee 2 a i ce ee ap 23
Pergande, Theodore, identification of Pee kf <a eeesedeetl= fists ane es te 39
PED SST yo oS ea a a 17
Petals smoothness an-obstacle to. keleps.--_....--.--<.--.2-bewa cows neo ene 26
Peedi alhessn, [Ryel tee nist: CYGUITI Gs aS SES epee Pa alk I) 7 er ge 16
LEEDS, TELS WG1GIe Se) YC TSi ae oan a 26, 39, 46
Planting, Be Hee ik Rete le be 19
Jasna Ve tai era rel force io: seat nS oe nh a re 13
Peete MN UEIOUS CO: COLLOM ae eee. bt ek ge et eb Le Oke Le 39
Pri PaCS IrUCeLO 1a beta Gilby. 2 2 = kos Se ete ow ei ste we ce eee 22
Pollen, Cee ae eM CUS a ee eed meres, MeN OE My to ot URN Sk 55
SAYER N EL Lah Vetiver eee Mn RoW ee Po SR NM ee ot ke 47
necessity for sexual maturity of vie oi Pe ai ed eee ee 55
ieollen-eatine liabi, deyelopmentss. 28! 25 Sele. lol ee es 63
Berea acer collected tae nr cusp oN ear 30
Proliferation, advantage only under conscious selection .........-.-....----- jill
best weevil-resisting adaptation -_.....2..2£...2¢2.-.:..206.25 9
diminution of power miarver buds. 2.2022. 2.25 2252-240. -.2 2% 51
PHech Ohl aVeEeaCr ecm areas 2.07 807 ie St ie ree ene 60
SID PUSS AV EN Se a Sie SO oh I RS Se a 46
POS ANeS, saya oe eeete es. SN Polat ote ay 49
UG OL een are ef amet 1h. 2 Eee) Se eee 58
ME VUUstandepolise relationesales- 9.884. 52.808 ees Fe 64
JCS G) aul Copia a Ms Rae are ee aR SR Oi a prea ys Lt 46, 49, 75
LESTOVE? (GOUM RONEN = Se che aL ae at ae ne et ced Oo ce ee i 60
EPI col eM ase ye for etn ms ee eee ee Soo Pee SS SS 60
Watieienouner elamieekeht 6.055. ce ubeeec use. MR ieol Pee 50
(BNE | OVO) S Rear k Us nS Fach fool ae a EO an Spr el ge re, Pe leg ea ag ap 55, 56, 59
pie Caller aRaeonauione -.- se 22 Ss ie Pe 49
CULE U ee ed he see ee iy IE ge ET I 48
Iter tissues Oh PUGS oss GoGo2 os et ee ee a ceo 46

86 WEEVIL-RESISTING ADAPTATIONS OF COTTON.

Page.

Proliferation; ‘probable‘ettects of culiuré*: 922202522 (22 eeceeece eee ae 50

summary of results of sitdy.. 22220 < se 2 5ce ee oe «49

time Tequired: 22 Hotes STs StS Se Bee ae ee eee es ee ee 60

Vales. De Sones Se kee aaa a ee ee ae ee ee ee ep Mile: 65

Protection afforded by adaptations, commercial value........--------------- 76

When Mmostieihectives.2-2- 5-2 s--es- eee 74

the involuere? $252 55h 2. ees ese oa ee he eee 37

touch linings. of chambers of bolls 2.222 -2 2.2222. 56

by Keleps;: efficiency: 222. citi 22 2 tense ae e ee ceeee 34, 35

of' seeds by lint ).2i2icc2 22h 2 ae ee at Se ee ee 65

Protective characters, first originated by cotton plant -.......--.------------ 68

general o8 st oe oe hs ee ee eee an oe ee ge ee eee ee Lt

Of bose Poe a ee eee See Se eee Sete 51

value of involticre: 2° 45222 Ses 26 oo Ss Saas aeee oe eee eee ot

Quaintance, A. L., observations ------ Pe POE aa Ch Sn ps ea nO a ys
Rabinalcottonyadaptamons 2) s- 5c ne (oe cent cee See eee eee ae 7

bolls fed*upon’ by boll weevils: ..25:2205..<s-2o222 2-2 eee 61

characters: 2: so 522. see ens coe eee eee cae ee eee ee 41

INAGTINGSS) ees 8 20 os SA ee PA See OSS SSE See are eee 25

AM VOMIGNES er eS eae ee PADS EE ES SPRO RE See ee ee ae 37, 38

MECTATICR Rs oe eee ete eee eee he ao ee ee See ee ee dl

Guatemalasantse (of. oo coer see eece aes ot ees ae. eee eee 39

CHOLA MOTO GE NU A Sg Pe ee 2p en Soke a Set Sol ey Deen OR ets 9, 38

GUSLOMIS/OLIndidns 22234 tose eee te See eae ee 24

Rain, effect, at time,of dloyertny':2 5252.5. 208 as se ae aa we ee 21

Redshank cotton, characters 242222 3252.52 525-5. ase = ee ee oe eee 53

Ae ECLA TION ASC s0 oe ons eee eee eee 31

Retalhuleuw district:of Guatemala, cotton planted -...-- <2... 5-8 ee 25, 34

Rivers cotton, character in (Guatemala 222-225-2425 065 o ee eee es 17

Rubber, Central American, branches compared with those of cotton......-.. 19

Sajal) plant often wisited by ketene <2 icess- 22 ontoc. eee eee een 37

Salama, Guatemala, cotton.culture of Indians. ......-22.52.25 scr -ssees-eeee 24

San Lueds: Gastemala, Seq island cotton. 2. - 2-22 <2 sae eee eee 24
adaptatione.<a- ies 4s sone ae ee 7

attacked by other insects -...-----.- 32

(iSGOVELY 2225-55 breu. . waste see ee 50

NeclariGs? oc. 5 peek Uae Bae 32

Seliwarz, UhecAc. OPSErVa HONS ssa nee ee ae eo eee tee eee ere 42,48

onjCubantcoulons — 2. 2525 a= ee ee eee 23

Sea: Islandscottien, Guatemalan, discovery. 2. 5-22 =-2-- = seine eee eee 50

mectanles. 3.2.2.2 4. eos ees 32

of San Lucas, Guatemala, annual flowering -.------------- 24

cottons, comparison of petals with Upland varieties -......------- 26

flaring Of squares’ 2.22.0 66s. eae pa eee oe ore 40

imvolucral bracts: 5.22.52. s See See Oe eee eee 37, 38

lacking in. protective:features.: .- 2. boise: Secece eee 4

less hairy. than’ Upland. vanieties! 2).2: e222. 44 eee 25

notimmune tor boll weevils 2=s2c8 4-6 as Se see eee eee 42

olbwlands)=. 2125 22e26 cee 2 cena (eee Ee eee 53

Origin S22 Wu eee hoe st Ssh ee ee a eee 8

precocity 1n,Gustemalassiaculcs -Seae See eee eee 17

smoothness a disadvantage to keleps -.....-------------- 25

Secanquim, Guatemala, cotton grown im vicinity ---..5-2--.22-<- --2S-225---- 15

exXpellimentsi a. eee eee Seer ape eee aes emeiae 39, 41

Seed; low germinationim Guatemalas -o2o-s 25 oo cea eee e Seee eee 15

Seeds, protective arrangement in Kidney cotton .......--.---..------------- 66

Selection, conscious, unconscious, natural, and artificial, discussion - -- ---- WAS Os ral

inscotton, time required: 22.2 2. =) anes eee seen ee eee 10

provided ‘by boll weevil: <2: .5-- 02 sacs etee = ae See eee ere 10

Selective influence ofibellli weevil 2-25. =~ 22+. = eae see es oe ee Ae 10

Short: season vanetlesiol cotton: soso. tee eee ee eee eee 12, 14, 22

Solenopsis picea, ant inhabiting Rabinal cottom-<.-2.-<--.------2s2-+2>-56-—= 39

Specific type, generalized, the product of diversity and interbreeding. --...-- 68
Squares, boll weevilinjuries:-=: .: ete eee ce oe See ee eee 41

flared and. fallen, countings? = pete a) Lace = See 45

Marine. 3 och St fo hth eee eee ee es ie ee 40, 41

INDEX.

Squares, multiplicationinieluster cottons-- 2-2. 2--- - 2-2-2 <5 lesene eee eee
small breeding places for- weevils: 22.22.2555 2...-202i..45..2-----
SL PeTlnOUe (cat TSICChOM Meee oe oe aR Sta sate alee alse sas ce
Vicar ou kay gu Cela tevo beets) veo ol hakos, 2 Oe ar eee eee ae eee ae ee
SLanninalat pe provseratio n= se eee eee ess oe Ean seein comes oes
Stipules of cuter bracts represetited by bractlets_...'...-...---2.--5--.----+-
SLORMPOOLV All ChiCshOmCOUsOnen eet we sees ae tt nis oor a sce eiemine Seer crc
PSmpenioma OUOS ;OISCUSSLON dice hess eee oa c's a no cicls Sea ee cee ones ss
Symbiotic specializations between plants and animals .-......-.----.-------

Tapinoma ramulorum, ant inhabiting Rabinal cotton ..............----.-----
Temperatures at localities where Kekchi cotton is grown
MerreliipeNexse ce SPOLIMents25— soe .a seems eaaiae ee ees om wince a asin ietc/oaneis S ore
Mexacteamlysachvent Or Weevil seer eee see meee Me ae oe a's Says Reen cece
Soupmerns wmebnod: ot checkimosweevillee aese 22 acjs0 toes cee soca te
sLhespesia, species! not attractive to: boll weevil -..-....-26 ses. esses ccs eee
iopmerapeeiect OL WeCVLLe 2s as cease seas sk Goce sais ow seco oS ane SSeS
SINCEVCOULONS, CUMONSIONSS<—\= sees hase oo eee Neem a stan a ws acess ae
GISCUSSIONE Saeeme ne acer eee n tienes Oe a Noe atte os scene 6

TMM UY. LO Wee Vile, TepORUGd s. a eee ence cee eck ~ esse eesne ses

rea Gree hr ern cru leRs ki fo N eed 2 c e

PANTS SLE NAGI IM) Sa lS viel ol gk eee ee ee ce ae oe

ING ScCOMeENLC CLUE DEMERS ar ee ema eee hy A SR SSE

THENELON TOV, CONE 1 C(O Spe a ea aN le ee al ee eee ne,

(See also Perennial cottons. )
Trelease, William, observations

Tucuru, Guatemala, Kidney cotton
Turkeys, boll weevil destroyers
Tyler, F. J., observations

United States cotton varieties, effect of Guatemalan conditions
SiOINeCOlbONA, ACAPIAGONS beeps. 8 he osccccini seuss Suet ow See ee cke
GHECE OL Chanperel Climate. ce. -nclooane Soasoc t= sceeelh uk fs fe
indeterminate habit in United States varieties .......-....--
native in Central America
COMBINE = = ci Doe eee ee HER ee hen Sen Tena ae tee
preference of keleps
secretion of nectar

Variations, climatic, in cotton
in Kekchi cotton

RiGiOnA hex we xperinenties = tench nes asthe 2 Soe Oe Se owen
Volunteer cotton, absence in eastern Guatemala
breeding of weevils

CHI Minny. cOMmeObONChODon= S625 sce oars Su Aalst ance hedole Jekedoes
exclusion of boll weevil from Mexican plateau
Wie hermiiardee shalemmentdas == s26 2208 Sse Sisk es Soe EN a del ee aed
Weaving by Guatemalan natives, use of foreign thread
Weevil. See Boll weevil.
Peel procmumnine Of Dolls 58 = ee Sec oe sn oclac ue be Seedenuic ceeds cased
Weissman, Professor, doctrine of inheritance
Winters, severe, no protection from weeyils

O

i ete ee

me 97-50

<5 oes, oh

: ea . , Hy _ igure a

Qe

Ee eee

ed Pk ers

ERS SY
ALY ed
re

SG ee F rae
: Borie

= = Sar
ara
yin

L¥ 4

+ eh

a ey *
i red
att a

is

Y

|

}

|
9 002 8

i)

“y —-*

ee