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U.S. DEPARTMENT OF AGRICULTURE.
BUREAU OF PLANT INDUSTRY—BULLETIN 10. 96.
B. T. GALLOWAY, Chief of Bureau.
TOBACCO BREEDING.
BY
A. D. SHAMEL
| AND
W. W. COBEY,
In CHarGE oF Topacco BREEDING EXPERIMENTS,
PLANT BREEDING INVESTIGATIONS.
IssuUED MarcH 12, 1907.
‘= CD Any ed
PAS AEs
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
IS HOLLG:
BUREAU OF PLANT INDUSTRY.
Pathologist and Physiologist, and Chief of Bureau, Beverly T. Galloway.
Pathologist and Physiologist, and Assistant Chief of Bureau, Albert F. ‘Woods.
Laboratory of Plant Pathology, Erwin F. Smith, Pathologist in Charge.
investigations of Diseases of Fruits, Merton B. Waite, Pathologist in Charge.
Plant Breeding Investigations, Herbert J. Webber, Physiologist in Charge.
Plant Life History Investigations, Walter T. Swinele, Physiologist in Charge.
Soil Bac teriology and Water Purification Investigations, Karl F, Kellerman, Physiologist
in Charge.
Beononic ‘Investigations of Tropical and Subtropical Plants, Orator F. Cook, Bionomist
in Charge.
Drug and Poisonous Plant Investigations and Tea Culture Investigations, Rodney H.
True, Physiologist in Charge.
Physical Laboratory, Lyman J. Briggs, Physicist in Charge.
Taxonomic Investigations, Frederick V. Coville, Botanist in Charge.
Farm Management Investigations, W illiam J. Spillman, Agriculturist in Charge.
Grain Investigations, Mark A. Carleton, Cerealist in Charge.
Arlington Experimental Farm, Lee C. Corbett, Horticulturist in Charge.
Sugar Bect Investigations, Charles O. Townsend, Pathologist in Charge.
Western Agricultural Extension, Carl S. Scofield, Agriculturist in Charge.
Dry Land Agriculture, E. Channing Chilcott, Expert in Charge.
Pomological Collections, Gustavus B. Brackett, Pomologist in Charge.
eee vestigations in Pomology, William A. Taylor and G. Harold Powell, Pomologists.
in Charge.
Experimental Gardens and Grounds, Edward M. Byrnes, Superintendent.
Seed and Plant Introduction. Investigations, David Fairchild, in Charge.
Forage Crop Investigations, Charles V. Piper, Agrostologist in Charge.
Seed Laboratory, Edgar Brown, Botanist in Charge.
Grain Standardization, John D. Shanahan, Expert in Charge.
Mississippi Valley Laboratory, St. Louis, Mo., Hermann von Schrenk, Expert in Charge.
Subtropical Laboratory and Garden, Miami, Fla., Ernst A. Bessey, Pathologist in Charge.
Plant Introduction Garden, Chico, Cal., Palemon H. Dorsett, Pathologist in Charge.
Cotton Culture Farms, Seaman A, Knapp, Lake Charles, La., Special Agent in Charge.
Editor, J. EH. Rockwell.
Chief Clerk, James EK. Jones.
PLANT BREEDING INVESTIGATIONS.
SCIENTIFIC STAFF.
Herbert J. Webber, Physiologist in Charge.
Alkali and Arid Plant Breeding: T. H. Kearney, Physiologist in Charge; L. L. Harter,
Scientific Assistant.
Corn Breeding: C. P. Hartley, Assistant Physiologist in Charge; E. B. Brown, Scientific
Assistant.
Cotton Breeding: D. A. Saunders and D. N. Shoemaker, Special Agents in Charge of Cot-
ton Laboratories, Waco, Tex.; R. L. Bennett, in Charge of Cooperative Work, Texas
Agricultural Experiment Station ; S. M. Bain, in Charge of Cooperative Work, Tennes-
see Agricultural Experiment Station ; E. B. Boykin, Special Field Agent; H. A. Allard,
Scientific Assistant.
Oat and Potato Breeding: J. B. Norton, Assistant Physiologist in Charge.
Tobacco Breeding: A. ID. Shamel, Physiologist in Charge; W. W. Cobey, Special Field
Agent; W. W. Garner, Scientific Assistant : W. H. Scherffius, Tobacco Expert.
9
~
96
EEPIER OF SEKaANSMIEPIAL
U. S. DeparTMENT oF AGRICULTURE,
BureEAv oF Puantr INpustry,
OFFICE OF THE CHIEF,
Washington, D. C., September 25, 1906.
Str: I have the honor to transmit herewith a paper on “ Tobacco
Breeding,” by Messrs. A. D. Shamel and W. W. Cobey, of the Plant
Breeding Investigations of this Bureau, and would recommend
its publication as Bulletin No. 96 of the Bureau series.
The tobacco-breeding work of the Bureau of Plant Industry has
now been under way for several years, and results have been obtained
which have attracted widespread attention and proved of very
great value to practical tobacco growers. This bulletin is intended
to summarize the results secured up to date and to place the
knowledge obtained before growers in such a form that they will
be able to understand it and apply it in the practical work of im-
proving their crops. The experiments have shown that tobacco can
be improved in many important ways, and the methods by which
such improvements can be produced are here described in detail.
The illustrations form a very important part of the publication
and are necessary to enable the grower to understand clearly the
character and improvements discussed in the text of the bulletin.
Respectfully,
B. T. GaLioway,
; Chief of Bureau.
Hon. James WItson,
Secretary of Agriculture.
96
B. P. I.—234.
POR VOCO hie DING:
INTRODUCTION.
The growing importance of the tobacco industry may be realized
from a brief summary of the estimates of the value of the crop in the
United States in the season of 1906. About 796,099 acres of tobacco
were grown, producing an average yield of 857.2 pounds to the acre,
or a total of 682,428,530 pounds. The average value of the crop was
10.0 cents a pound, or a total of about $68,232,647. While it is
almost impossible to comprehend the magnitude of the value of the
‘manufactured products of tobacco, a glance at the total figures may
convey some idea of the development of this great and distinctively
American industry. In 1900 the total value of the manufactured
products of tobacco was $283,076,546. - These products may be divided
into three general classes, of which the values were as follows: Cigars
and cigarettes, $160,223,152; chewing, smoking, and snuff products
$103,754,362; stemmed and rehandled tobacco, $19,099,032. In the
manufacture of these products 142,277 people were employed, who
earned a total wage of $49,852,484. In addition to the tobacco grown
in the United States there was imported into the United States in the
year ended June 30, 1906, $4,143,192 worth of tobacco in a manutfac-
tured condition and $22,447,514 worth of unmanufactured prod- |
ucts, making the total value of the importations during this period
$26,590,706. During the same time the exports of manufactured
tobacco were valued at $5,410,480, and of unmanufactured tobacco
at $28,808,367. In 1891 the tobacco industry furnished almost
$50,000,000 revenue to the Federal Government, and the revenue from
this source now amounts to about one-eighth of the Government’s
total net receipts. ;
The United States now grows by far the largest quantity of tobacco
produced by any country in the world. While tobacco was grown by
the first settlers in the colonies and was one of their principal cash
crops, the extensive development of this industry has been a matter of
comparatively recent years. The introduction of tobacco into the
different sections of the United States, with their widely varying
if
96
§ TOBACCO BREEDING.
conditions of soil and climate, has resulted in the production of types
adapted to the soils and conditions of these sections, as well as supply-
ing a product for the varied manufactures now. demanded by the
consumers of tobacco. Improvements in methods of culture, curing,
and fermentation have resulted in the production of tobacco having
an increased value, but the most important factor in the development
of more valuable tobaccos has been the production of improved
varieties by seed selection and breeding. The production of these
improved varieties adapted to local soil and climatic conditions has
made possible the rapid development of the industry and enabled the
United States in a comparatively short time to rank as the foremost
tobacco-producing country in the world.
The prosperity of the tobacco industry as a whole and of the
growers in particular depends on the development of improved
varieties of tobacco adapted to the demands of manufacturers and
consumers. There is no crop which responds so readily to breeding as
tobacco, as has been proved by the experiments of the writers, and it
is further true that without careful selection and breeding there is
no crop which so quickly deteriorates in yield and quality. The
extent of the areas in the United States in which the conditions of
soil and climate are suitable to tobacco culture is almost unlimited,
so that it seems possible that by giving attention to the production of
varieties adapted to those conditions this country can continue to
produce an increasingly large yield of valuable tobaccos.
The experiments of the writers have shown that it is possible to
increase the yield and improve the quality of the crop by seed selec-
tion and breeding. The methods of breeding worked out in the
course of these experiments are simple and practical and can be
carried out by every grower with little or no extra cost in the pro-
duction of the crop. The fact that tobacco is perfectly self-fertile
and that self-fertilized seed produces more uniform and_ better
developed plants than seed resulting from cross-fertilization within
the variety makes it possible by the adoption of proper methods of
saving seed to make rapid progress in the improvement of the crop.
Improvement in the shape, size, and quality of leaves or increase
in the number of leaves borne by the individual plants, all of
which can be attained by breeding, means increased profits to the
erowers and manufacturers, and therefore is of vital interest to al!
who are interested in the production, manufacture, and consump-
tion of this crop.
The production of new varieties of tobacco by hybridization and
selection is a most important phase of tobacco breeding. The new
hybrids of native New England varieties with standard foreign-
erown varieties, combining certain valuable characters of both par-
96
GREAT VARIABILITY OF TOBACCO PLANTS. 9
ents, described in this bulletin, are good illustrations of the use of
breeding in the improvement of the tobacco crop. The making
and testing of hybrids are matters of experiment and require con-
siderable time and expense, but experience has shown that the
results justify the necessary expenditure.
The production of improved breeds of live stock and varieties of
fruits and cereals, in fact, of all crops, might be cited to prove the
importance of applying the principles of breeding to the tobacco
crop. It is only recently that systematic breeding experiments have
been undertaken. It is hoped that the results of the experiments
cited in this bulletin will serve as a means of creating general inter-
est in this subject and of inducing investigators, breeders, and grow-
ers to turn their attention to the further improvement of their crops.
Tobacco growers in the sections where these experiments have
been carried on have generally adopted the improved methods of
bagging carefully selected seed plants and of separating the seed,
and they are using the improved varieties of tobacco produced in
the course of these investigations. In most of these districts cer-
tain men have become interested in the careful and systematic breed-
ing of tobacco.
THE GREAT VARIABILITY OF TOBACCO PLANTS.
Under the intensive system of cultivation necessary for the pro-
duction of profitable crops of tobacco, the condition of the soil,
the fertilization, and the cultivation are fairly uniform so far as
individual fields are concerned. In those tobacco-growing sections
where the best grades are produced it is a common practise to grow
tobacco year after year on the same field without rotation, instances
being known where more than fifty consecutive crops have been pro-
duced on the same field. This system of cropping enables the grow-
ers to become thoroly familiar with the character ‘of the soil in all
sections of the fields, so that any inequality in fertility can be reme-
died by the judicious application of manures or commercial fertili-
zers, or by methods of cultivation. Notwithstanding these favorable
circumstances for the production of uniform plants, a careful study
of the plants in these fields reveals a great lack of uniformity as
regards all characters. This lack of uniformity is particularly
noticeable with respect to the variation in number, size, venation,
shape, and habit of growth of the leaves borne by individual plants,
the time of ripening of the leaves on the same plant and on different
plants, the number and size of the suckers, and the structure and
arrangement of the flowers and flower heads. From the practical
standpoint, there is no more important problem in tobacco culture
than the production of uniform crops. A lack of uniformity in the
96
1 re et
10 TOBACCO BREEDING.
crop not only results in a low yield, as a whole, and more especially
of the best and most profitable grades of the cured and fermented
product, but also increases the cost of sorting out the different
types of leaves into their respective grades for market, the expense
of which must be borne directly or indirectly by the grower.
The principal cause of the lack of uniformity in tobacco is cross-
fertilization. In tobacco, as in all other crops, seed resulting from
cross-fertilization produces many plants unlike either parent. There-
fore such seed is undesirable for the general planting of a crop
where uniformity is so important a factor. Where the tobacco seed
plants are grown without protection from cross-fertilization some
of the flowers are cross-fertilized by insects or other agencies. De-
sirable plants may thus be crossed with undesirable plants in the >
same field or in adjoining fields, and the plants grown from the seed
thus produced are usually extremely variable, some of them resem-
bling the desirable plants from which the seed was harvested, others
resembling the inferior plants from which the pollen was carried
for crossing, while the remainder are of an intermediate type, un-
suited to the purpose for which the crop is grown, and therefore
causing a loss to the grower. The writers have observed number-
less cases in different tobacco-growing sections where several dis-
tinct and worthless new types appeared in the fields, the plants of
which were grown from carefully selected seed. These undesirable
types could only be accounted for by the accidental crossing of the
seed plants the year preceding or at some previous time. The cross-
ing of individual plants of the same strain, even if both are desirable
plants, results in undesirable variations, many of which are appar-
ently reversions to earlier and unimproved types of tobacco.
In those varieties of tobacco in which the buds are removed long
before the flowers open on all of the plants except those saved for
seed production, or where early topping is practised, the opportunity
for the crossing of the flowers borne by the seed plants with other
plants in the same field is almost wholly limited to the seed plants.
However, it frequently occurs that late or diseased plants, or pos-
sibly sucker branches that have been overlookt, develop flowers
which open at just the right time to allow insects to carry the pollen
from these flowers to the seed plants and thus effect cross-fertiliza-
tion. There is little doubt that many of the plants of irregular and
unusual types are produced as a result of this kind of cross-fertiliza-
tion.
An important cause of variation in tobacco plants is the use of
immature seed. Many growers cut off or harvest the seed heads
before all of the seed pods have turned brown; hence, before ma-
turity. The writers have observed hundreds of instances where the
96
GREAT VARIABILITY OF TOBACCO PLANTS. Vek
seed plants have been cut off while many of the flowers were still in
bloom. On such seed heads seed pods in all stages of maturity can
be found. Some of the pods are fully ripe and contain mature seed,
while others have not fully developed. Much of the seed is imma-_
ture and contains little food for the nourishment of the plantlet.
These seed heads are frequently thrashed out with a flail or the pods
are crushed by the hands in order to shell out the seed. In this way
the immature seed is mixt with the ripe seed sown in the seed
beds. In the seed beds the immature seed frequently sprouts earlier
than the mature seed, and the early seedlings grown from such seed
are naturally used for transplanting in the field. Such plants have
a great tendency to vary, in some cases being very early, and as a
rule having leaves that are small, coarse, and wholly undesirable for
any purpose. These weak, immature tobacco seeds, according to
careful and extensive observations by the writers, produce plants
which are more subject to certain diseases, particularly the mosaic
disease, than are plants grown from mature seed.
The excess of plant food in the soil where heavy applications of
barnyard manure and commercial fertilizers are used is usually
thought to produce variations in the plants. This variation is usually
shown by an increase in the size of the leaves, which is generally
correlated with changes in color, flavor, and other characters. In
these cases there is usually a tendency for the type of plant to break
up, so that the uniformity of the crop is disturbed. Where it is
necessary to use large quantities of fertilizers in the growing of a
profitable crop, the inclination to variation induced by this intensive
system of cultivation must be controlled by the most rigid selection
of seed from the type of plants best adapted for the purpose for
which the tobacco is grown.
The change of soil and climatic conditions, particularly the taking
of tobacco seed from southern or tropical conditions to the north,
is a fertile source of variations in tobacco. The fixation of a uniform
type in this case requires several years of acclimatization, supple-
mented by selection of seed from the desirable plants.
In the production of improved varieties of tobacco by breeding, va-
riation in type can be secured by crossing, and by continued saving of
self-fertilized seeds from plants most nearly reaching the growers’
ideal of perfect plants uniform types can be fixt. Growers will fre-
quently find plants that are markedly better than the rest of the plants
in the field, so that by selecting these desirable variations a steady im-
provement in the yield and quality of the crop can be effected. Vari-
ation, therefore, is a basis for selection in an experimental way, but
in practise every effort must be put fofth in order to secure uni-
96
12 TOBACCO BREEDING.
formity of the plants in the field and thus produce the most profit-
able crops. .
The variations in tobacco plants may be divided into two general
classes—variation in type and individual variability within the type.
The causes of the variations in type, or striking variations, include
crossing and change of soil and climatic conditions, particularly the
change of seed from the Tropics to temperate regions. The causes
of individual variations within the type include the fortuitous va-
riations or inherent tendency to variability, methods of soil fertil-
zation and cultivation, maturity of seed, and various local conditions.
With an understanding of these conditions the grower can to a great
extent control the degree of variability by methods of saving seed,
systems of cultivation, and other practical methods of culture.
THE INTRODUCTION AND ACCLIMATIZATION OF VARIETIES.
The introduction of the seed of standard foreign-grown varieties
of tobacco has been the source of increased wealth and prosperity
in certain tobacco districts of the United States. In other regions
such importations have resulted in great financial loss to the grow-
ers, which in most cases has been due to a lack of knowledge of the
effect of the change of soil and climatic conditions on the particular
type of tobacco grown. The writers have had an unusual opportu-
nity in the course of their work to observe the behavior of crops
grown in different tobacco-growing sections from imported seed, and
have conducted extensive experiments in taking seed from one dis-
trict to another, with a view to securing definite information on
this subject for the benefit of the growers. The results of these
observations are presented here for the guidance of tobacco growers
who desire to use foreign-grown seed or who wish to change their
seed.
The western Florida and southern Georgia Sumatra tobacco in-
dustry is an illustration of the successful introduction of a foreign-
grown variety of tobacco. Tobacco growers in this region secured
small samples of the seed of the Sumatra variety of tobacco from
the island of Sumatra. At first small experimental crops were
grown and seed saved from the best plants in these crops. In the
course of this experimental cultivation it was noticed that the
plants grown under the partial shade of trees in freshly cleared
fields produced finer and more desirable leaves for cigar wrappers
than the plants grown in the open. This fact led to the erection of
an artificial shade over the fields, made of slats laid on a suitable
framework. This method of growing tobacco was introduced about
1896 by Mr. D. A. Shaw, of Quincy, Fla. Later, other growers
96
INTRODUCTION AND ACCLIMATIZATION OF VARIETIES. 13
used a coarse cheese cloth as a substitute for the slats. The shade
method of growing tobacco in this region has developed rapidly,
and at the present time several thousands of acres of tobacco are
grown under either slat or cloth shade, and the industry has become
established on a profitable and successful basis. During this time
considerable attention has been paid to the production of a uniform
type of tobacco adapted to the climatic and soil conditions of this
section by the saving of seed from carefully selected plants of the
Sumatra variety.
When Sumatra seed was first introduced into Florida the variety
broke up into a number of different types, some of which were de-
sirable, while others were undesirable. By reason of the small crops
grown from such seed, the loss to the growers from the production
of undesirable types of plants was not very great. The growers
naturally saved for seed those plants which produced the most de-
sirable types of tobacco, and as a result of continued selection of
this kind a fairly uniform type of tobacco which was adapted to
the local conditions in this section was secured. As the demand for
this Florida-grown Sumatra tobacco developed, resulting in in-
creased acreages, seed was at hand which was thoroly acclimatized
for planting the larger area devoted to this crop. From time to
time the tobacco planters in this region have obtained small quanti-
ties of seed from Sumatra, but in such cases this seed has been
grown in a very limited way in very small fields until it has been
acclimatized and uniform types have been secured by seed selection.
About the time of the Cuban revolution it became apparent that
the supply of Cuban-grown tobacco for the use of cigar manufac-
turers in the United States might become limited by reason of the
unfavorable conditions for tobacco growing then prevailing in Cuba.
Under these circumstances it was thought to be a propitious time
to introduce the growing of Cuban tobacco into southern Florida,
where the conditions of climate and soil were believed to be similar
to those of Cuba. Considerable public interest was aroused in this
project, and as a result large quantities of Cuban-grown seed were
secured and planted in certain sections of Florida. . The crops raised
from this seed proved to be a disappointment to the growers. The
change of soil and climatic conditions resulted in the breaking up
of the type of the Cuban variety into a large number of sorts, some
of which were desirable, while others were undesirable. Many of
the plants developed a branching habit of growth, bearing very
small, undesirable leaves of poor quality, resulting in a very low
yield of an inferior tobacco. One of the main causes of failure
was the lack of understanding on the part of the growers of the
effect of the change of conditions on the type of tobacco and their
96
laa A ET
A RR RS mR ae
14 TOBACCO BREEDING.
neglect to appreciate the necessity of securing strains of plants by
seed selection of the desirable types adapted to the particular con-
ditions of soil and climate in southern Florida. If the acclimatiza-
tion of these strains had been accomplished by seed selection in
small fields, with little loss to the growers, the strains could have
been grown on a more extensive scale with better chances of success.
In order to illustrate the necessity for the acclimatization of a
variety of tobacco before it 1s grown on an extensive scale, the
successful experiments of the Bureau of Soils in the introduction of
Cuban tobacco in Texas may be cited. After a previous unsuccess-
ful attempt by farmers in Texas to grow Cuban tobacco from
freshly imported Cuban seed the Bureau of Soils began systematic
experiments in growing small fields of tobacco and saving the
seed of the most desirable plants according to the method described —
in this bulletin. In these crops certain plants were found which
produced leaves possessing the flavor and aroma desired in a high-
grade filler tobacco. The seeds from these plants were saved under
bag, and their product has been found to possess the desirable char-
acters of the parent plants. ~This tobacco has been sold at profitable
prices, and the area devoted to the growing of this crop is being
gradually extended in order to meet the demands of the manufac-
turers for this grade of filler tobacco. In northern Florida the
tobacco growers, as a result of their experience with the imported
Sumatra seed, experimented in growing, in the open, small fields of a
cigar filler tobacco of a variety the seed of which was originally
introduced from Cuba. This variety of Florida filler tobacco is
now being grown extensively and profitably in that section.
The best illustration of the effect of a change of climatic and
soil conditions upon the character of a variety of tobacco is found
in the experience of tobacco growers in the Connecticut Valley in
the planting of Florida-grown Sumatra seed and seed of the
Sumatra variety imported from the island of Sumatra. As dis-
cust in an article upon the improvement of tobacco by breeding
and seed selection in the Yearbook of the Department of Agriculture
for 1904,* tobacco growers in the Connecticut Valley in the seasons
of 1901 and 1902 grew extensive crops from seed introduced from
Florida and Sumatra. In a careful examination of these fields it
was found that the change in conditions had resulted in the breaking
up of the type of the variety, so that several distinct types of tobacco
were found growing in the same fields. Some of these types of
plants produced well-rounded leaves, with fine venation and the
elasticity, strength, gloss, grain, and other characters necessary in
a@Shamel, A. D. Yearbook of the Department of Agriculture, 1904, pp. 435-452.
96
INTRODUCTION AND ACCLIMATIZATION OF VARIETIES. 15
a high-grade cigar wrapper tobacco. However, many of the types
of plants produced long, narrow, coarse, pointed leaves, wholly
unsuited for cigar wrapper manufacture. In the case of another
inferior type it was found that the leaves would not burn, altho
the remaining characters were those of a desirable grade of tobacco.
It -was impossible to sort out this type, even by the most careful
inspection of the crop, and, as a result, when the manufacturers
wrapt cigars with leaves of this type and found that the wrapper
would not burn, the quality of the entire crop was condemned.
Certain other types of plants produced leaves of such thin texture
or ight body that when wrapt on cigars and allowed to dry out the
wrapper frequently broke, or when
the consumer carried the cigars 1n
his pocket the wrappers were easily
injured. |
One of the most striking types of
plants produced in the crops grown
from this imported seed was the
Belgian type, an illustration of —
which is shown in figure 1. In this
case the plants bore leaves measur-
ing from 30 to 46 inches long and
only from 5 to 10 inches wide.
These leaves, as shown in figure 2,
were very pointed in shape, with
coarse, angular veins, and as the
cured tobacco lacked the appearance Fic. 1—Belgian type of Connecticut Suma-
necessarv for a cigar-wrapper to- tra tobacco plant. These long, narrow
De : leaves with oblique veins, coarse texture,
baeeco its production was a total burn very poorly, and after curing light
loss to the growers. The variation green color are almost absolutely worth-
: : 2 i less for clgar-wrapper purposes. Thistype
In type Was accompanied by differ- appeared in crops grown in the Connecti-
ences in time of maturity, so that cee ory tones srowne cue
e seed. :
the cost of the growing and har-
vesting of these crops was greater than in the case of uniform ~
crops. The mixture of types was accompanied by great variation as
regards the individual plants of each type. In many cases plants
bearing 25 leaves were found growing by the side of plants pro-
ducing 10 leaves. Marked variations in size and shape of leaves
and in the number of suckers borne by the individual plants were
observed, and as a result it was found that the comparatively small
number of desirable types could not make up for the loss in the pro-
duction of undesirable and worthless grades of tobacco. As a nat-
ural consequence of this condition the extensive culture of this vari-
ety of tobacco from imported seed has been abandoned, and the grow-
- 96
ao oe
a ea cn ain
16
TOBACCO BREEDING.
ers now have small fields and are selecting those plants producing
the most desirable grade of cigar-wrapper tobacco with a view to
securing strains which are adapted to the conditions of the Connecti-
cut Valley. In the experimental fields of the Bureau of Plant Indus-
try, covered with cloth shade, where seed of de-
sirable plants has been saved under bag for three
seasons, uniform strains, which are absolutely
free from the unusual or distinct types observed
in the fields from which the original selections
of seed were made, have been produced.
A few of the growers of the Sumatra variety
in the Connecticut Valley introduced Cuban-
grown seed and used it for planting their general
crops. In these fields the breaking up in type
was not so noticeable as in the case of the Suma-
tra variety, but the effect of change of conditions
in the variety was shown in the production of
so-called freak plants. These plants had a
branching, or suckering, habit of growth, bearing
very small, sharply poimted, coarse leaves that
were worthless for cigar-wrapper purposes. In
a careful study of the plants in these fields it was
found that at least one-third of the entire crop
consisted of these freak plants.
In one of these fields the writers made selec-
tions of seed plants of the most desired type,
bearing the size, shape, and general character of
leaves adapted for cigar wrappers. This seed
was saved under bag, and a similar plan has
Fic. 2.—Typical leaf of
Belgian type of tobacco,
showing the character-
istic shape, venation,
and other characters of
this variety which are
been followed up to the present time.
In Plate I, figure 1, the original crop raised
from freshly imported seed from which the seed
wholly unsuited for ci-
gar-wrapper manufac-
ture. The presence of
such types of leaves re-
duces the value of the
crop and is detrimental
_ to the reputation of the
variety of tobacco in
which they are pro-
duced.
selections were made is shown. In Plate I,
figure 2, is shown a crop grown on the same field
after two generations during which the seed was
saved under bag. As can be seen from the
illustrations, this method of seed selection and
bagging has produced a uniform type of to-
bacco without the freaks and other undesir-
able types of the original crop. It is fortunate that on this farm
the planter saved seed in the open for his own use from the same
field. The crop grown from such seed was visited during the season
of 1905 by the writers, in company with Dr. H. J. Webber and several
tobacco growers, and was found to contain a large proportion of
freaks; in fact, about the same proportion as the crop grown from
96
STRUCTURE AND ARRANGEMENT OF FLOWERS. 17
freshly imported seed. In other words, the seed saved under bag pro-
duced uniform strains adapted to soil and climatic conditions in this
section, while seed saved in the open and subject to cross-fertilization
with freaks and other undesirable types produced about the same pro-
portion of freak plants as the crops grown from the freshly imported
seed.
The writers during the past season planted in Florida Connecticut-
grown seed of the Sumatra variety. It was found that while there
was a noticeable change in the shape of leaf and in some minor char-
acters in the Florida-grown tobacco, there was no violent breaking
up of type or indication of unusual variability. This experiment
and other observations have led the writers to believe that the effect
of changing seed from the north to the south is not accompanied by
such marked changes as when seed is taken from tropical conditions
to northern latitudes.
In summing up the observations on this subject it can safely be
said that it is a dangerous policy to plant large crops of tobacco
with imported seed or with seed from a very different section. In
most cases it has resulted in failure and caused considerable loss to
the growers. The general crops should be planted from seed pro-
duced under the same conditions as the crop which is to be grown. If
it is necessary to change the seed or desirabie to test imported vari-
eties, it should be done on a small scale, followed by a most careful
selection of seed plants, and the seed should be saved under bag, safe
from cross-fertilization.
THE STRUCTURE AND ARRANGEMENT OF FLOWERS.
A careful study of the tobacco flower is one of the most essential
factors in the beginning of tobacco breeding. Successful results,
particularly in the production of new varieties, can seldom be ob-
tained until one becomes familar with the structure of the parts of
the flower and the manner in which these parts perform their sev-
eral functions. A full realization of the ease with which crossing
takes place can only be obtained in this way, and, as has been pre- |
viously stated, the prevention: of promiscuous cross-pollination is
of first importance in the production of a desirable and uniform type
of tobacco. _
The tobacco flowers are arranged upon a branching determinate
flower head, which appears when the middle leaves are about half
grown and continues to develop and produce new flowers during the
rest of the life of the plant. Figure 3 is a diagrammatic sketch of
a tobacco flower, showing the parts of the flower and the general way
in which pollination takes place. The calyx (a) is the outer, green,
five-parted, floral envelop at the base of the flower which serves to
15507—No. 96—O7 Mm
2
,
18 TOBACCO BREEDING.
protect the flower in the bud. The corolla (6) is the delicately
colored floral envelop inclosing the reproductive organs of the flower.
Tts color tends to attract insects, which are the principal agents in
cross-poliination. Next inside the corolla are the five stamens, which
are the male reproductive organs of the flower. Each stamen consists
of the filament (7), supporting the anther (7) in which the pollen
grains (4) are produced. The central organ is the pistil, or female
part of the flower. The terminal enlarged portion (q) is the stigma.
The pollen grains (/) adhere to the
surface of the stigma (g) and germi-
nate, sending an extremely minute tube
(7) down thru the central conductive
tissue (h) of the style (7). This tube
extends into the cavity of the ovary (d)
and finds its way into the ovule (7)
thru a small duct or micropyle (m),
where fertilization takes place. Other
ovules (e) are fertilized by other pollen
tubes. These ovules develop into seeds
after fertilization. The ovary is two-
celled, with a fleshy central placenta
(c) on which the ovules are borne. The
early capsules mature- always before
flowering ceases. The shape of the del-
cately colored corolla is somewhat tubu-
lar, or, perhaps, more nearly lke an
elongated funnel. It is comparatively
small from the basal end to a point
about two-thirds the distance to the ter-
minal end of the flower. At this point
it enlarges suddenly to more than twice
the size of the basal part of the tube
(fig.83). It is composed of 5 petals,
TES ear een ene which coalesce to form the corolla tube,
and separate only at the extreme end.
The tobacco flower is symmetrical. The number of sepals and
stamens is always the same as the number of petals, but these floral
circles do not remain constant, varying rather indefinitely in different
strains and even among individuals of the same strain. Trimerous
flowers, or flowers with three parts in each flower circle, have been
found growing on the same plants with pentamerous flowers, or
those having five floral parts. This is the exception, however, and
not the rule.
The tobacco flower is naturally self-fertile, and plants grown from
96
STRUCTURE AND ARRANGEMENT OF FLOWERS. 18S)
self-fertilized seed are always stronger and more vigorous than those
from cross-pollinated seed when the crossing is within the variety.
In Sprengel’s discourse on the cross and self pollination of plants
the statement is found that “nature seems to have wished that no
flower should be fertilized by its own pollen.” Later, Darwin stated
that “ nature abhors perpetual self-fertilization,” but, unlike Spren-
gel, recorded a number of exceptions’ to this rule, and tobacco was
among them. The experiments of the writers conclusively substan-
tiate the findings of Darwin in this connection. They have found
self-pollination in the case of tobacco to be most desirable in all cases.
A very interesting phenomenon of growth takes place in the fila-
ments of the stamens immediately after the opening of the flowers,
which can be taken- as an evidence of the natural self-fertilizing
habits of the plants. An examination of the flower just previous to
the time of opening will reveal the fact that the pistil is longer and
extends up beyond the stamens, but when the anthers open and the
stigma becomes receptive a very rapid growth of the filaments takes
place, which causes the open pollen sacks to be pushed up past the
stigma, and in almost all cases they come in direct contact with the
stigma in passing upward. This gives an opportunity for at least
a portion of the pollen grains to adhere to the viscous surface of the
stigma and for self-fertilization to take place, as shown in figure 3.
It is just before this process occurs or while it is in progress that
there is danger of, or opportunity for, cross-pollination. The open
flower contains a small drop of nectar at the base of the corolla tube,
which is sought by honeybees, bumblebees, and humming birds, as
well as by many species of minute insects, all of which carry pollen
from flower to flower and from plant to plant in their constant search
for the honey-like substance secreted in the corolla tube. In passing
in and out of the flowers the bodies of the bees and other insects and
the beaks of the humming birds become dusted with pollen, which is
transported by them to the pistils of the next flower visited. The
ovules are as readily fertilized by pollen from the surrounding
plants as by the pollen from the flower in which they are produced.
This continuous crossing necessarily results in the introduction and
intermixture of poor and undesirable varieties in our best strains of
tobacco.
The observations of the writers plainly show the absolute necessity
for protecting the flowers of the seed plants from cross-pollination.
Careful experiments have demonstrated that in many instances the
stigma of the tobacco flower remains in a receptive condition for
three or four days. This condition results in a twofold disadvantage
when no protection is used against cross-pollination. In the first
place, it affords abundant time and opportunity for complicated
96
ster Ne ern toe
20 TOBACCO BREEDING.
crossing, for each flower is visited many times a day by various in-
sects and often by humming birds; and, secondly, it brings about con-
ditions favorable for the production of seed of weak vitality. Pre-
vious experimenters have pointed out the fact that the best seed is not
produced as a result of premature or late pollination, either of which
is likely to occur in the case of tobacco flowers under natural con-
ditions. When fertilized only by pollen of the same flower, the
pollination takes place at exactly the right time, or when the stamens
push past the receptive stigma, which results in the production of a
superior grade of seed. :
The readiness with which tobacco flowers can be cross-fertilized
greatly facilitates the opportunity for producing new and valuable
varieties by artificial cross-
ing. In the course of the
experiments here recorded
it has been found per-
fectly possible to combine
certain desirable qualities
found in different strains
and at the same time to
eliminate some of the un-
desirable characters by pro-
ducing hybrids between
strains of tobacco.
The method of cross-pol-
lination used in the experi-
ments of the writers is to
FG. 4.—Three tobacco flowers at proper stage foremascu- Yemove all capsules, open
lation, and the scissors and forceps used in emasculat- flowers and flower buds
ing fiowers. The corolla of the central flower has been y
opened in order that the anthers may be conveniently from the flower head ex-
removed. The flower on the left has been emasculated cept those which are in the
preparatory to cross-pollination.
| proper stage of develop-
ment to open within the following twelve or fifteen hours. In
preparing these remaining flowers they must be carefully opened
and emasculated by the use of a scalpel, small scissors, and a fine pair
of forceps, as illustrated in figure 4. Great care must be taken in re-
moving the anthers before they have dehisced, in order to avoid
injury to the stigma. The emasculation should be done in the after-
noon, after which all of the flowers must be carefully covered with a
thin paper bag as a protection against insects or other agencies
whereby pollen might be transferred to them. In the forenoon of
the following day the emasculated flowers should be ready for polh-
nation, but the exact time for applying the pollen must be determined
in the case of each individual flower by the appearance of the viscid,
sticky fluid on the surface of the stigma. The pollen from the male
96
STRUCTURE AND ARRANGEMENT OF FLOWERS. yA
parent plant can be best applied to the stigma of the female with the
point of a scalpel or other sharp instrument. When apphed with a
brush there is danger of some of the pollen grains adhering to the
hairs of the brush after each operation, resulting in considerable
mixture of pollen, but where the scalpel is used there is no difficulty
in removing all the pollen after each operation. The paper bag
must be replaced over the flowers as soon as they have been pol-
linated, and must be allowed to remain until the seeds have set and
all danger of crossing has past.
In crossing it is not essential that both of the parent varieties be
grown in the same community. Pollen from tobacco flowers when
thoroly dry will keep for several weeks or longer without deteriora-
tion. The writers have sent pollen thru the mails a distance of more
than a thousand miles with perfectly satisfactory results. When
not intended for immediate use, it should be harvested when perfectly
dry and carefully taken off the anthers after they have dehisced
and become dried out. These dry anthers may be put in small
vials, and the pollen kept long enough for all practical purposes,
provided the vials are carefully corked and kept dry.
The large number of seed produced in a single pod and on a single
plant makes it possible to obtain definite results from selection or
hybridization in tobacco much more quickly than in the case of most
other plants. Careful counts show that from 4,000 to 8,000 seeds are
produced in a single pod of normal size, and an estimate of the aver-
age number of pods on each plant shows that the ordinary tobacco
plant produces from 500,000 to 1,000,000 seeds. In many cases the
writers have secured from 1 to 14 ounces of seed from a single plant
when the seed has been saved under bag according to the method out-
lined in this bulletin. This large number of seeds gives an excellent
opportunity for testing each selection or cross on a large scale. The
quantity of seed produced varies inversely with the number and size
of leaves on the plant. The production of a large number of good-
sized leaves 1s almost invariably accompanied by the production of a
small quantity of seed.
On account of the large quantity of seed produced by a single
plant under normal conditions and the fact that the various charac-
ters of a tobacco plant are inherited so strikingly and uniformly by
its progeny the following year when the seed is saved under bag, pro-
tected from cross-fertilization, it is possible for the tobacco grower
to secure uniformity with a considerable degree of improvement in
type, quality, and yield by one year’s selection. One plant often fur-
nishes enough seed for an entire crop, and the plants raised from this.
seed always produce a very uniform lot of tobacco when cross-fertili-
zation is not allowed to take place.
96
99, TOBACCO BREEDING.
THE NECESSITY FOR INBREEDING.
Tn the season of 1903 the writers, in company with Dr. H. J. Web-
ber, visited the tobacco fields of the Connecticut Valley in response to
a request of the growers for assistance in the production of uniform
strains of tobacco by breeding and seed selection. During the survey
of this region with a view to gaining an idea of the variability of the
varieties of tobacco, it was determined to inaugurate a series of ex-
periments in a practical way for the investigation of the methods of
saving seed.
In view of the results of the investigations of Darwin and others
on the comparative vigor of growth, seed production, and other char-
acters of tobacco plants raised from seed obtained by cross and by self
fertilization * the seed of select plants of the different types of tobacco
was protected from cross-fertilization by inclosing the flower heads
with a hight but strong form of paper bag. Other seed plants were
saved without such protection, as is ordinarily done by the tobacco
growers. The seed harvested from these seed plants was saved sepa-
rately, stored in small glass vials adapted to this purpose, and labeled
according to the system now in use by the breeders in the plant breed-
ing investigations of the United States Department of Agriculture.
The record of the number of leaves, size, thickness, shape, and color of
leaves, number of suckers, height of plant, habit of growth of leaves
and plants, time of maturity of leaves and seed, and other characters
was kept according to the system used by Doctor Webber, modified
by the writers for use in keeping a pedigree of tobacco varieties.
The seed of the plants finally selected for experimental purposes
was sown in ordinary seed beds, separated into many small sections
by thin board partitions, each of which was capable of holding 500
seedlings. The seedlings from these separate seed-bed plats were
transplanted to separate rows or plats in the experimental field, each
row or plat being carefully labeled so that the plants could be traced
directly back to the original seed plants. The manuring, or fertili-
zation, and preparation of the soil in the experimental field and the
transplanting, cultivation, and harvesting of the plants were all
conducted with the greatest possible care to give all of the rows or
plats equal opportunity for growth. For instance, the seed of all of
the plants of a variety was sown the same day, and at the proper
time the seedlings of this variety were all transplanted the same day.
At the time of harvest the leaves of the individual rows or plats were
primed or the plants cut on the same day, and the leaves or plants
were hung in the curing shed, so as to get as nearly uniform condi-
a Darwin, Charles. Cross and Self Fertilization in the Vegetable Kingdom,
pp. 203-215.
96
NECESSITY FOR INBREEDING. ; 23
tions for curing as were consistent with the practical handling of the
crop. The leaves of plants selected for seed were harvested sepa-
rately and labeled so that the product of each plant could be intelli-
gently used in comparative tests of the cured and fermented crop.
This labeling process involved considerable extra work and attention
in the field, curing sheds, and warehouses, but was absolutely neces-
sary for a definite selection of seed plants for the next season’s use,
based on the character of the fermented tobacco.
The rows or plats of plants grown from seed of individual plants
saved under bag, 1. e., self-fertilized seed, showed remarkable uni-
formity in type, size, shape, and appearance of leaves, habit of
growth, and all other characters, and conformed closely to the type
of the parent plants from which the seed was saved.
Plate II, figure 1, shows a type of parent plant and Plate I,
figure 2, the progeny of this plant, raised from self-fertilized seed.
From this illustration it can be seen that the transmitting power of
tobacco is most strongly marked and the progeny of plants raised
from inbred seed remarkably uniform in all characters, every plant
closely resembling the parents. In the hundreds of tests of this char-
acter which have been carried on by the writers during the past three
seasons, not only in the Connecticut Valley but in Maryland and
Florida, the benefits to be derived from using inbred tobacco seed
have been confirmed and emphasized. It is true that some plants
have the power of transmitting their characters to their progeny
more strongly than others, but on the whole every case under obser-
vation has offered additional evidence of the value of the practise of
saving tobacco seed under bag, free from possible cross-fertilization.
The continued saving of self-fertilized seed for three seasons
has furnished no evidence of a decrease in the rate of growth or
constitutional vigor of tobacco plants as a result of this practise.
On the other hand, by reason of the selection of the best plants in
the different varieties every season there has been a marked increase
in the productiveness and the general vigor of constitution of the
varieties under consideration. This conclusion is emphasized by the
vigorous and productive strains of Connecticut tobacco shown in
Plate III. :
Self-fertilization is the closest possible degree of inbreeding, and
it is the general impression that this practise is usually associated
with a loss of vigor of growth, with a predisposition to disease, and
other undesirable results. In tobacco, so far as our experience goes,
this does not happen, and the exact opposite of this condition obtains,
viz, that inbreeding is beneficial to the general development of the
variety.
It is unfortunate that it is impossible to present tabular data at
96
24 TOBACCO BREEDING.
the present time showing the behavior of plants raised from arti-
ficially cross-fertilized seed within the variety in comparison with
plants raised from self-fertilized seed. The principal object of this
work has been the achievement of practical results, so that the
opportunity for scientific observations and experiments has been
necessarily limited. However, the writers have had the privilege
of making careful observations on the results of saving seed from
plants grown under large field tents and comparing the plants raised
from such seed with the plants raised from self-fertilized seed.
Under these tents there is little opportunity for cross-fertilization
with other varieties, except thru the small doors opening into these
tents, which are kept closed all of the time when persons or teams
are not actually passing thru them, so that there is little hkelihood
of bees or other insects passing in and out. The probability is that
the cross-fertilization that takes place is wholly between the plants
saved for seed in these tents or with other plants under these shades
that are in bloom at the proper time for cross-pollination.
The comparison of the plants raised from seed saved under these
field tents and exposed to cross-fertilization with the surrounding
plants and of plants of the same variety raised from seed protected
from cross-fertilization by paper bags shows that self-fertilized
seed produces more uniform, vigorous, and productive plants than
the open-fertilized seed, which is to a greater or less extent cross-fer-
tilized between plants of the same variety.
It appears that the cross-fertilization of tobacco seed, even tho it
occurs between good individuals, has a tendency to seriously break
up the type. Along with the variability of type induced by cross-
fertilization, it frequently happens that many freak plants resembling
the wild species appear; these can only be explained with our present
knowledge of the subject as reversions. Such freak plants are not
usable for profitable manufacture, and consequently are a source of
loss to the growers.
The size and weight of seed from the inbred plants are equal to
and in most cases greater than the seed saved from open-fertilized
plants. In a series of comparative tests of the two kinds of seed
in the case of four varieties grown in the Connecticut Valley it was
found that the inbred seed was heavier and larger than the cross-
fertilized seed. The total quantity of seed harvested from the
open-fertilized plants usually exceeded that of the inbred plants.
This was due to the fact that in the case of the inbred plants more
of the seed-bearing branches were removed than where the plants
were allowed to set seed under natural conditions, in order to adapt
the seed head for the best possible development under the paper
bags. Where an equal number of seed pods was examined for
96
NECESSITY FOR INBREEDING. 25
vield of seed the inbred seed equaled or exceeded in quantity the
cross-fertilized seed in the variety. In the case of hybrids or in
the crossing of two distinct strains or varieties the yield of seed,
as well as rate of growth of the hybrid plants, was greater than thai
of the inbred seed and plants. It is true that some of the improved
inbred strains produce but little seed compared with unimproved
types of the same variety. Inbred strains have been selected for
increased yield and number of leaves, which seem to be correlated
with lessened seed production. The same correlation holds true
where open-fertilized strains have been selected for increased num-
ber and total yield of leaves.
The rate of germination of the inbred in comparison with the
cross-fertilized seed was thought to be slower in some of the experi-
ments carried on in the season of 1904. However, further compari-
sons have failed to bear out this conclusion, and it is the behef of
the writers, based on careful observations on this subject, that the
inbred seed sprouts as rapidly as the cross-fertilized seed. It seems
probable that in the cases observed by growers in 1904 a difference
in moisture content of the rotted apple-tree fiber, the medium used
for sprouting, was the cause of the apparent differences in time of
sprouting. So far as the writers’ observations go, the inbred seed
produces more rapidly growing plants than the open-fertilized seed,
and consequently earlier plants for transplanting. There is no doubt,
Turther, that the inbred seed produces a larger proportion of seed-
lings for transplanting at one time than the open-fertilized seed,
which is an important matter to the tobacco grower, who is fre-
quently forced to wait for seedlings on account of the lack of uni-
formity of plants in beds sown with open-fertilized seed.
Darwin’s conclusions on the comparison of tobacco plants raised
from inbred and cross-fertilized seed for three years are as follows: ¢
Taking the plants of the three generations altogether, the crossed show no
superiority over the self-fertilized, and I can account for this fact only by sup-
posing that with this species, which is perfectly self-fertile without insect aid,
most of the individuals are in the same condition as those of the same variety
of the common pea and of a few other exotic plants which have been self-fer-
tilized for many generations. In such cases a cross between two individuals
does no good; nor does it in any case, unless the individuals differ in general
constitution, either from so-called spontaneous variation or from their pro-
genitors having been subjected to different conditions. I believe that this is
the true explanation in the present instance, because, as we shall immediately
see, the offspring of plants which did not profit at all by being crossed with a
plant of the same stock profited to an extraordinary degree by a cross with a
slightly different subvariety.
@Parwin, Charles. Cross and Self Fertilization in the Vegetable Kingdom,
Dp. -210:
96
26 TOBACCO BREEDING.
These conclusions of Darwin were based upon greenhouse and gar-
den tests, where, of course, it was not possible to study and compare
the characters of quality or the value of the tobacco from the inbred
and cross-fertilized seed. The observations of the writers upon to-
bacco grown in the field under normal conditions in the different
tobacco-growing sections bear out the conclusions of Darwin on this
subject, and show, further, that the inbred seed produces more profit-
able crops of tobacco than the seed resulting from open or cross fer-
tilization within the variety.
THE IMPROVEMENT OF THE SHAPE OF LEAVES.
The shape of the leaves is a very important factor in determining
the value of all classes of tobacco, and is of first and particular im-
portance in cigar-wrapper varieties. Many varieties which possess
some of the most desirable characteristics of high-grade wrappers are
totally valueless for this purpose on account of the narrowness of the
leaves. From such leaves it is impossible to cut cigar wrappers eco-
nomically. The manufacturer of cigars demands a leaf which is wide
and well rounded at both ends. This shape admits of the best op-
portunity for cutting into wrappers of the desired shape and size
with the least possible waste, while the long, pointed leaf will yield
very few wrappers, and a very considerable proportion of it must be
consigned to the waste pile.
The long, pointed leaf is not only undesirable because of its shape,
but the texture toward the basal end is poorly adapted for cigar
wrappers and the grain is usually unevenly distributed. In such
cases a large part of each leaf can be utilized only for binders or
low-grade fillers. A striking example of leaves of this character
may be found in the case of many strains of Connecticut and of |
Pennsylvania Broadleaf varieties. When working these varieties
the manufacturer expects to cut wrappers from the middle portion
and tips of the leaves only, while the remainder of the leaves, often
half or more, must be used as binders or for filler purposes. A
wider leaf and one which is more nearly round would yield many
more wrappers to the pound and would be proportionately more
valuable.
In addition to being wide, with well-rounded tips, the best wrap-
per leaves must have small, fine veins which are widely separated
and which form an obtuse or right angle with the midrib. The
veins in narrow leaves extend along down the leaf toward the tip,
are coarse, and present a very unattractive appearance when wrapt
on cigars, while in the case of wide leaves the veins usually extend
out toward the edge of the leaf and are almost perpendicular to the
midrib, smaller in size, and wider apart. In some of the strains of
96
IMPROVEMENT OF SHAPE OF LEAVES. Da fl
Broadleaf tobacco which have been improved by careful seed selec-
tion and breeding the veins are sufficiently wide apart to allow
wrappers for cigars of standard size to be cut between the veins.
Such wrappers have a very smooth, attractive appearance on cigars,
and where they can be cut in this way the waste material from
each leaf is exceedingly small. Figure 5 illustrates the superior
value of the wide over the narrow form of leaf for cutting wrappers
economically. Attention is also called to the character of venation
Fic. 5.—Diagrams showing the superiority of broad over narrow leaves for cigar-wrapper purposes: A,
broad leaf; wrapper cuts numbered 1, 2, 8, 4,5,6,7,and 8. B, narrow leaf; wrapper cuts numbered
la, 2a, 3a, and 4a. Waste indicated by hatching. Not only do the broad, round leaves yield more
cigar wrappers, but on account of the venation and other characters they produce wrappers of
superior quality.
in the two leaves shown. It will be observed that the veins extend
out almost directly toward the edge of the leaf from the midrib in
the case of the wide leaf (A), while in the case of the narrow leat
(B) the veins run upward, and, consequently, when used as wrap-
pers injuriously affect the appearance of cigars.
The variability of the plants in the field in respect to shape of
leaf is found upon close observation to be more striking than the
variability in many other characters. The variability of strains of
96
TES LIE OS OO,
28 TOBACCO BREEDING.
tobacco grown from the seed of the same variety and under similar
conditions as respects shape of leaves is shown in Plate IV. It is
very important that this variability be reduced to the minimum,
and the writers have found that it is possible to greatly reduce the
variability by systematic seed selection. Plants producing leaves
which are very long and narrow are frequently found growing be-
side others with well-rounded leaves of a desirable length. Plants
bearing leaves of the ideal cigar-wrapper shape and those that were
totally worthless on account of their shape, as well as many grada-
tions between these extremes, have been found growing side by side.
In the case of a field of Florida tobacco grown from freshly im-
ported Sumatra seed a similar variability was observed in the sum-
mer of 1905. The production of leaves of undesirable shape results
in a direct loss to the grower and manufacturer alike. The cost of
production to the grower is no greater where the leaves are all of
uniform size and shape, and the cost of grading is greatly reduced.
In nearly all varieties of cigar-wrapper tobacco, most of the leaves
are small and narrow near the basal end and this portion of the
leaf is seldom wide enough for wrapper purposes. Figure 5, A,
shows a leaf wide at both ends, from which wrappers may be cut
down to the extreme basal end, thus avoiding the waste which can
not be avoided in the form of leaf shown in figure 5, B. It is im-
portant to produce the form of leaf shown in figure 5, A, not only
because it will yield more wrappers to the pound and _ necessitate
very much less waste in cutting, but because more wrappers to the
acre may be obtained.
The variability in the shape of leaves on the same plant is often
very marked, and may be as readily corrected by proper methods
of seed selection as the variation among the individual plants in
the field. The size and shape of the individual leaves on almost
all plants vary more or less, but on some much more than others.
An occasional plant will be found on which the leaves are compara-
tively the same size and shape from the top to the bottom of the
plant, while in other cases there are marked differences in this
respect. Where this uniformity is found the top leaves are seldom
as thick or heavy as where there is a lack of such uniformity, and
therefore a larger percentage of the leaves is adapted for cigar-
wrapper purposes. ;
By selecting for seed the plants possessing leaves of the most
desirable shape from top to bottom and protecting them from cross-
fertilization, it is possible to produce a crop which will be uniformly
hke the parent plant. It can be plainly seen that this will result
in a larger yield to the acre of much more valuable tobacco because
of the uniformly well-shaped leaves, best adapted to cigar-wrapper
96
i
MODIFICATION OF SIZE OF LEAVES. 29
purposes, and this may be accomplished with no additional expense
to the grower.
The shape of the leaf in certain types of smoking tobacco largely
determines its adaptability to both soil and market conditions. In
Maryland it has been found generally true that a broad leaf gives
best results on very light sandy soil, and is best adapted to the
demands of the German market, while a somewhat narrower or
longer leaf is more desirable on heavy clay soil; from this latter
type the highest grades of red tobacco are produced to meet the
requirements of the markets of France. In the case of Maryland
tobaccos the shape of leaf js usually correlated with the number of
leaves, there being more leaves to the plant where they are narrow
than in cases where they are broad. The writers have observed many
exceptions to this rule and have found that by keeping this point in
mind when selecting seed plants it 1s possible to find round-leaved
plants producing a large number of leaves, and to procure varieties
from these plants which will produce a large number of uniform
leaves and at the same time a grade of tobacco which will be adapted
to the demands of the market for which it 1s grown.
It is within the power of the tobacco grower to produce the shape
of leaf best adapted to the purposes for which his tobacco is grown,
and to continually improve the shape and gradually bring it up to
the ideal of a perfectly shaped leaf, by carefully selecting seed
plants year after year which produce leaves most nearly approach-
ing this ideal. In all cases if uniform types are to be produced
cross-pollination must be prevented, in order that the progeny the
following year may inherit only the characters of the desirabie
parent plants.
THE MODIFICATION OF THE SIZE OF LEAVES.
The modification and control of the size of tobacco leaves is of
almost equal importance to the improvement of their shape, and
the size is so intimately associated with the shape that both features
ean be dealt with along the same lines in the improvement of
tobacco by breeding and seed selection.
The purpose for which the crop is grown must always determine
the most desirable shape and size of the leaf, and the individual
grower must decide for himself what size and shape will be best
adapted to the local market demands. The importance of producing
a comparatively definite and uniform size of leaf is well recognized
by the manufacturers of all classes of tobacco. In the case of the
Maryland Smoking tobacco grown for export purposes it is difficult
to procure a leaf which is too large for the highest market demands, -
especially when it is grown for the French market. In most cases
96
30 TOBACCO BREEDING.
the leaves are too small. This defect may be remedied to a con-
siderable extent by selecting for seed those plants which have the
largest leaves, and at the same time this will result in a material
increase in the yield of the crop. When grown for plug wrappers,
the size of the leaf is as important and worthy of as careful con-
sideration on the part of the grower as when grown for cigar wrap-
pers. In the manufacture of certain brands of plug tobacco the
entire side of the leaf is used for one wrapper, which method is
often preferable to using large leaves which have to be cut into two
or more wrappers. Where this system is followed, leaves are de-
manded which are comparatively narrow and of sufficient length to
cover the standard size of plug with the least possible waste.
A eareful study of the size of wrapper desired by the manufac-
turer will give the grower a very definite idea of the most desirable
size of leaf to produce, and by selecting plants having this style of
leaf for seed the grower is enabled to produce uniformly the type of
tobacco which will be best adapted to his market conditions.
In cigar-wrapper varieties of tobacco the size is of as much impor-
tance as the shape of the leaf. A short, wide leaf is always the kind
most in demand, and has the advantage of being much less suscepti-
ble to injury in the curing barn. The. manufacturers of certain
brands of cigars prefer to cut only two wrappers from each leaf,
and for this reason demand a very small, round leaf. Most man-
ufacturers prefer a leaf sufficiently large for cutting two or more
wrappers from each side, for the reason that nearly all classes of
clgar-wrapper tobacco may be used more economically in this way.
The size of Sumatra leaf most desired at present is about 16 inches
long and sufficiently wide to admit of the most economical cutting.
When leaves become very much larger than this there is danger of
coarse venation, altho this can be very largely controlled by select-
ing for seed only those plants which produce leaves that have small,
fine veins.
The question of venation is very intimately associated with both size
and shape of leaf, and a certain correlation seems to exist between
these characters. The writers have been able to produce types hav-
ing leaves of desirable shape and size in which the venation is fine
and in every way desirable. The experiments that have been con-
ducted with this end in view prove beyond a doubt that these im-
portant characters may be successfully correlated and largely con-
trolled by methods of selection and saving seed.
In curing tobacco in the barn the size of the leaf has been found to
be an important factor. This has been clearly shown in the breeding
experiments in the Connecticut Valley during damp curing seasons.
One of the objects sought in Connecticut has been to secure a shorter
96
MODIFICATION OF SIZE OF LEAVES. 31
and rounder leaf than is now being produced in the Havana Seed and
Broadleaf varieties. Numerous crosses have been made and hybrids
produced with this end in view, and considerable progress has been
made in securing a rounder leaf in the native varieties by careful
seed selection: It has been invariably observed that these round-
leaved varieties and strains have suffered much less injury from
pole-sweat than the old standard varieties. This difference is attrib-
uted to the fact that in the case of the old long-leaf varieties the
leaves after wilting hang down close around the stalk and adhere
to one another, thus preventing the proper circulation of air when
it is most needed for successful curing; while in the shorter, round-
leaf types, the leaves stand out from the stalk, do not adhere closely
together, and admit air freely to all the leaves on the plant, thus
preventing in a large measure the injurious effects of pole-sweat or
house-burn. The importance of the size of leaf from this standpoint
can not be too strongly emphasized. The loss in the Connecticut
~ Valley, as well as in many other sections of the country, due to pole-
sweat often takes away the profit of the crop and is keenly felt by
tobacco growers. The best crops are occasionally totally ruined by
pole-sweat after they have been grown successfully and put into the
barn in good shape. Therefore it can be plainly seen that the pro-
duction of shorter, rounder leaved varieties in sections of the country
where pole-sweat is disastrous will result in great profit to the tobacco
growers and packers. Crops which have been badly injured in the
barn are a source of endless trouble, and are very expensive to sort
and pack successfully.
For cigar-filler purposes a comparatively small, short, and thick
leaf is demanded. The small leaves are usually thicker and have
better body and a very much better aroma and flavor than large, thin
leaves. It has been definitely demonstrated from observations made
by experimenters on the island of Cuba and from the observations of
the writers made in certain filler districts of the United States that
the best and most aromatic fillers are always obtained from plants
producing comparatively small leaves. Plants which in a way seem
to represent dwarf types or strains almost invariably produce leaves
which have a much higher aromatie flavor than can be obtained from
plants of the same variety producing larger and finer leaves.
In an attempt to improve the aroma of some of our domestic filler
types thru breeding and selection the Department of Agriculture is
endeavoring to produce new types of Cuban tobacco with very small
leaves, with the belief that such types will have a superior aroma and
will excel the filler grades which are now being grown in this coun-
try. These experiments have not advanced far enough to admit of
any very definite conclusions, but they have indicated very clearly
96
32 TOBACCO BREEDING.
that it is possible to produce better fillers by originating and per-
petuating small-leaved varieties of tobacco. The yield from such
types has been comparatively small, but by setting the plants closer
together it is believed that there will be very little decrease in the
yield to the acre in the production of small leaves uniformly thruout
the crop.
The great variation in the sizeof leaf which is found in nearly all
tobacco fields makes 1t possible to breed up and fix varieties which
will produce uniformly the size of leaf most desired to meet special
market demands. Plants producing small leaves are found growing
along with those producing large leaves when all are, as far as we
know, of exactly the same variety and grow under equal and uniform
conditions. This variation is undoubtedly due to promiscuous acci-
dental cross-pollination which has taken place in preceding genera-
tions. This variation in size as in shape of leaf also occurs much
more strikingly on some individual plants than on others. Plants
may be found in all tobacco fields with leaves of comparatively the
same size and shape from the top to the bottom of the stalk, while in
the majority of instances they are much smaller near the base and
top than the middle of the stalk. By selecting seed plants that pro-
duce leaves which are uniformly of the desired size and shape from
top to base of plant and by covering the flower heads with light
paper bags, leaves very uniform in this respect may be grown the
following year from seed saved in this manner.
Any fonacee grower will recognize immediately the advantages to
be gained by producing types of tobacco in which the leaves on all
of the plants are uniform in size and shape and where the leaves on
the individual plants are likewise uniform in this respect from the
top to the bottom of the plant. The yield of the crop will be mate-
rially increased, as will the value of the tobacco, while the cured
product from such fields will be much more uniform in the packing
house and the cost of handling proportionately reduced. The writers
have already secured striking uniformity in some of the best strains
of cigar and smoking tobaccos grown from seed which they have se-
lected carefully and systematically for three years, and have found a
considerable increase in the yield and value of the crop grown from
such varieties.
A recognition of the importance of producing this uniformity is
emphasized by the great number of demands made upon the writers
for seed of these improved strains. It is easily within the power of
tobacco growers to improve their present strains of tobacco in the
shape and size of leaf, as well as in other characters, by selecting
for seed the plants which are most nearly perfect in these respects
and by saving the seed under bag according to the methods outlined
96
CONTROL OF NUMBER OF LEAVES. 33
in this bulletin, in this way preventing intermixture with undesirable
strains by accidental cross-pollination.
THE CONTROL OF THE NUMBER OF LEAVES ON INDIVIDUAL
PLANTS.
The variation in the number of leaves borne by individual plants
is just as marked as the variation in size and shape, but the size and
shape are not always correlated with the number of leaves. In a gen-
eral way it has been the observation of the writers that in cigar-
wrapper tobaccos the plants which produce the best-shaped leaves
usually produce more than the average number of leaves. The varia-
tion in the number of leaves on individual plants grown in the same
field may be almost invariably attributed to the lack of systematic
seed selection, to crossing, and to the use of a large proportion of
light, weak seed in planting. The variation may be correlated with
the height of the plants or the length of the internodes, or both.
Different strains of the same variety are extremely variable in respect
to the number of leaves produced, and until pure strains are devel-
oped no very great degree of uniformity in the number of leaves
borne by individual plants in the crops may be expected. The pro-
duction of strains true to type and uniform in the number of leaves,
as well as other characters, is made possible by the careful selection
of seed.
The control of the number of leaves is directly associated with the
yield of the crop, and bears a very important relation to success in the
handling and curing processes. The possibility of procuring a larger
number of desirable leaves on each plant thru careful selection of
seed is no longer doubtful, as is clearly borne out by experiments in
tobacco breeding. An increase in the production of leaves borne by
individual plants has been effected without any increase in the height
of the plants and with no detriment to the quality of the tobacco.
The reduction in the height of the plants is especially important in
Sumatra tobacco grown under shade. It is difficult to prime or pick
the top leaves from plants over 7 or 8 feet high, and it would not be
advisable for the grower to produce plants which must be topt
above that height. The most convenient height for a tobacco shade is
about 9 feet. A tent higher than this would be difficult to build, and
would be more lable to damage from severe windstorms; hence the
necessity for keeping plants below this height by growing more
leaves on each plant or by producing plants bearing shorter inter-
nodes. The Sumatra and Cuban varieties have a tall habit of
growth, with long internodes, but respond readily to methods of
breeding in the production of shorter stalks and shorter distances
between the leaves.
15507—No. 96—O7 Mm 3
34 TOBACCO BREEDING.
In all the varieties of tobacco which the writers have improved by
seed selection and breeding the internodes are short: and the number
of leaves proportionally greater in the improved strains. In a care-
ful count of the number of leaves to the plant in a good field of.
Sumatra tobacco the average was found to be between 19 and 20,
while the records made in the breeding plats of strains of tobacco
originally grown from the same seed as the general field where these
leaves were counted show that the number of leaves was increased by
two years’ selection to an average of between 23 and 24. The breed-
ing plats and the general field were grown under exactly the same
conditions in order to eliminate any influences outside of the results
of careful seed selection for the production of a greater number of
leaves. ‘The leaves produced on the plants giving an increased num-
ber were equal in size and more desirable in shape than those from
stalks producing a smaller number.
The increase in yield due to the production of a greater number of
leaves on individual plants and to shortening the internodes may be
secured by systematic seed selection with no additional cost to the
grower. Aside from the increase in yield, the quality of the leaf when
there is a large number of leaves borne by the stalks is usually better
than when the stalks produce but few leaves. This is particularly
true in cigar and high-grade smoking’ tobaccos. None of the im-
proved types of Sumatra tobacco have leaves sufficiently close together
to cause any deterioration in the quality or texture of the leaf during
the curing process. In the case of certain types of export and plug
tobaccos and in some of the northern-grown cigar-tobacco varieties
an increase in number of leaves is not desirable, for the reason that it
is conducive to pole-sweat when the crop is being cured. It is further
true in the case of these varieties that if the number of leaves is in-
creased without shortening the internode, the plants will become too
tall for expeditious handling. Therefore, it 1s necessary in certain
varieties of tobacco to keep the leaves down to a certain definite num-
ber, with a desirable length of internode. 7
It is entirely possible for the grower to control largely the number
of leaves by careful seed selection and in this way produce uniformly
the plants which give the number desired. Care must always be taken
in selecting for a large number of leaves not to increase the number
at the expense of leaf uniformity. Only plants having leaves uni-
form in size and shape should be selected for seed purposes, and this
selection must be kept up with unremittent persistency from year to
year in order to hold constant the characters of improved strains of
tobacco after they have been produced.
A large number of leaves to the plant is almost invariably closely
correlated with a much lessened tendency to sucker and with de-
96
PRODUCTION OF NONSUCKERING TYPES. 35
creased seed production. The plant food in such cases goes to the
leaves, where it is most needed, and not into the production of suckers
and of seed, which would be a loss to the grower. A large growth of
leaf greatly retards the growth of suckers, and in some instances types
have been produced which were comparatively suckerless—i. e., types
which produced only very few and small suckers. These types are
desirable not only from the standpoint of an increased leaf produc-
tion, but the expense of suckering is in a-_large measure eliminated.
The habit of growth of the leaves, whether erect, or at right angles
to the stalk, or drooping, greatly influences the number of “sand” or
ground leaves obtained from the crop. When the leaves are drooping
or pendent on the stalk the tips of a number of the lower ones come in
contact with the ground and are often covered with sand or beaten
and bruised by heavy rains, and are therefore partially or totally
damaged. This loss of the lower leaves of the stalk can be very
largely overcome by carefully selecting for seed those plants on which
the leaves have an upright or erect habit of growth. This very
important point in the habit of growth of the plant is often over-
lookt, but can be easily controlled by systematic selection. In view
of the fact that the sand leaves are not nearly so valuable as those
which have not been injured in this way, it is highly desirable that
this habit of growth of the plant be kept constantly in mind when
selecting plants for seed purposes.
The number of leaves on plants of a drooping habit of growth is
sometimes greater than where the leaves grow erect or in an upright
position, but where a large number of the lower leaves are badly
damaged a larger number of the best grade of wrappers may be ob-
tained from plants producing a somewhat smaller number of leaves,
but all erect. Individual plants producing a large number of the
desirable erect leaves may be found, however, and such plants should
be saved for seed under bag in order to propagate the strain the fol-
lowing year.
THE PRODUCTION OF NONSUCKERING TYPES.
The number and size of suckers borne by individual tobacco plants
are subject to considerable variation. In making selections of seed
plants in many tobacco fields the writers have found plants bearing
from 8 to 12 large suckers, and in the same fields other plants pro-
ducing only one or two small suckers. In Plate V are shown two
plants growing side by side in the field, at about the same stage of
maturity, one of which bore five large suckers, while the neighbor-
ing plant bore only one small sucker. Instances of this kind are
common in most tobacco fields. As can be seen in the illustration the
nonsuckering plant has a larger number of more rounded leaves
96
36 TOBACCO BREEDING.
than the suckering plant, which condition is usually true in all such-
cases. . | |
The production of many large suckers is usually correlated with
the development of few, heavy, dark, and usually narrow, pointed
leaves. This condition is explained on the ground that the large
sucker branches take from the plants the elements of plant food
which otherwise would be utilized in the development of many
broad, round leaves. The possibility of securing nonsuckering types
of tobacco was suggested in the course of a series of experiments in
the improvement of cigar-wrapper tobaccos. In the selection of seed
plants great care was exercised to pick out those bearing the largest
number of rounded leaves with fine veins. In the course of the
study of the progeny of these plants it was observed that few suckers
were produced by the most desirable types of plants. The continued
observations on this subject have confirmed the conclusions that
there is a correlation between the number, shape, and character of
the leaves borne by individual plants and the number and size of
suckers produced by these plants.
The number and size of the suckers produced by the plants in all
tobaccos is an important practical problem from several standpoints.
Owing to the dwarfing and otherwise injurious effect of the suckers
it is necessary to remove them by breaking them off, or to “* sucker ”
the plants, as the process is commonly called. There is great danger
of breaking, tearing, or injuring the leaves during the suckering
srocess, and this causes much loss in cigar-wrapper varieties, as the
injured cigar-wrapper leaf is rendered practically worthless. A care-
less laborer frequently causes great loss to the grower during the
process of suckering the plants. Owing to the fact that the suckers
do not develop on all of the plants at the same time and consequently
can not all be removed at once, it is necessary to go over the field
several times during the season in order to remove all of them.
The cost of suckering is one of the important items of expense in
the cultivation of tobacco. Therefore the production of nonsuckering
types is an economic problem of great importance, not only by
reason of the reduction in the cost of growing the crop, but from the
fact that the nonsuckering types usually produce a larger yield of a
more desirable quality of tobacco than the suckering types.
It has been found possible to produce uniform strains of different
varieties of tobacco having but few and small suckers by saving the
seed from nonsuckering plants under bag. As an illustration of the
possibility of the growers producing such types the experience of one
of the writers in the improvement of the Connecticut Broadleaf
tobacco may be cited. In these experiments desirable plants were
selected for seed in 1903, producing round leaves of fine, silky texture
96
PRODUCTION OF EARLY VARIETIES. 37
and few suckers. ‘The crops raised from this seed were found to
produce but few suckers, the progeny of the different plants varying
somewhat in this respect. From the strains producing the best type
of leaves and bearing the least number and smallest size of suckers
nonsuckering plants were again selected and the seed saved under
bag in 1904. In the season of 1905 it was found that the progeny of
these selections were almost .free from large suckers. In one strain
in particular only a few very small suckers, none of which grew more
than 4 inches in length, were produced. The plants raised from
ordinary seed of the same variety in the same field produced many
large suckers, and as usual it was necessary to sucker the crop several
times during the season. The remarkable difference in the sucker-
ing and nonsuckering habit has become so well fixt in this particular
strain that a limited distribution of the seed was made for testing
during the season of 1906.
It has been suggested that by saving seed from sucker branches
strains of tobacco are developed which produce an increasingly large
proportion of suckers; in other words, that sucker seed tends to
produce suckering types of tobacco. In experiments with plants
raised from seed saved from the central flower cluster the writers
have observed little or no difference. As a rule, however, it has been
found that the seed pods in the central flower cluster contain more
large and heavy seed than the pods borne by the sucker branches, so
that where seed is not carefully separated in order to secure only
heavy seed for planting it is probably the best practise to save seed
from pods borne by the central flower cluster of the seed head.
THE PRODUCTION OF EARLY VARIETIES.
Early maturing varieties of tobacco are of particular importance
to northern tobacco-growing districts. Owing to the fact that
frost kills the plants it is necessary for northern farmers to grow
varieties which will mature between the time of the last frost in
the spring and the first frost in the autumn. After the tobacco
crops have been harvested and hung in the barns the curing processes
are carried on most favorably during warm weather. The length
of time required for the completion of the curing varies with the
variety grown, the purpose for which the tobacco is to be used, and
the weather. Under normal conditions, however, the natural curing
period extends from four to eight weeks. It can readily be seen,
therefore, that early-maturing varieties are likely to have more
favorable conditions for curing than late varieties, as has proved
to be the case in the experience of the tobacco growers in northern
districts.
96
38 TOBACCO BREEDING.
Another fact of importance in this regard is the likelihood of
late-maturing varieties being injured in the field by autumnal storms.
The earlier the crops can be harvested, the less is the probability
of injury by severe rain, wind, or hail storms. In one district of
the Connecticut Valley in the season of 1905 a severe hailstorm at
about the usual time of harvest completely destroyed all except the
early-maturing tobacco, which had been harvested and hung in the
curing sheds. This experience is common to other northern tobacco
regions and emphasizes the value of early-maturing varieties.
The uniformity in time of maturing of the individual plants in
the fields is an important practical matter. In those districts where
the tobacco crop is harvested by cutting off the plants near the
ground all of the plants in a given section of the field must be cut
off at one time. The immature plants can not be left to ripen and
the early-maturing plants can not be harvested before the rest of
the plants in the field. Overripe or underripe tobacco is likely to
be of poor quality. In cigar-wrapper varieties the overripe leaves
lack elasticity, gloss, and strength. ‘The underripe leaves are likely
to have uneven color and are susceptible to injury by various fun-
gous and bacterial diseases. It is very important, therefore, that the
‘individual plants in the field ripen uniformly, so that they can be
harvested at one time without loss or injury.
The lack of uniformity in the maturity of leaves borne at the base,
middle, and top of the plants is a cause of loss in value of the crop to
the growers. As a rule the bottom or so-called “sand” leaves ripen
first, the middle leaves next, and the top leaves last. In the varieties
of cigar-wrapper or smoking tobaccos, especially where the entire
plant is harvested at one time, the overripe sand leaves and the im-
mature top leaves on such variable plants are inferior in value to the
middle leaves. As stated, the color of these sand and top leaves is
usually poor and undesirable, and there is also generally a corre-
sponding inferiority in the texture and quality of these leaves. ). The valve
(ce) is connected directly with the seed receptacle (e). The seed
receptacle consists of a 1-inch glass tube (¢) about 14 inches in length,
cemented in the reducer (d) with plater of Paris. At the extreme
bottom of the glass tube e and just above the top of the valve (c)
a fine wire gauze is fastened. The object of this gauze is to prevent
the seed from falling into the valve trom the receptacle, and there-
fore it is necessary to use a wire gauze with very small mesh. An
ordinary gas pipe coupling (7), about 3 inches in length and slightly
larger than the tube e, is firmly cemented to the top of the tube to
serve as a support for the tube g. The tube g is of glass the size
of tube e and about 6 feet in length. The apparatus can be sup-
ported by a convenient frame, which may be fastened to the wall or
set up wherever desired.
The bellows and tubing for this apparatus may be procured from
any chemical supply house, and the remaining parts from hardware
stores. They can be easily put together and the apparatus set up
in the proper manner by anyone who wishes to use it. A complete
device of this nature should not cost more than $5, a very small
sum compared with the benefits to be derived from getting rid
of the light and undesirable seed. In the successful operation of
this apparatus the following method should be employed: Pour
about 1 ounce of the tobacco seed to be separated into the seed
receptacle, and by means of the foot bellows pass a current of air
of sufficient strength thru the entire apparatus. The strength of
the current of air may be regulated by the globe valve so as to blow
out the desired proportion of the hght seed. The light seed is blown
out thru the top of the tube and the heavier seed falls back into the
seed receptacle. The degree of separation may be controlled accu-
rately by means of the valve, the length of the tube, and the work-
ing of the foot bellows. A much more complete separation may be
made by the use of a long tube than where a short one is used.
This simple apparatus serves to completely eliminate the evil re-
sults associated with the use of light and inferior seed. It is thoroly
practical in every way, and delicate enough in its operation to sepa-
rate the smallest kinds of seeds according to their individual speci-
96
60 TOBACCO BREEDING.
fic gravity. One apparatus is sufficient to separate seed for an en-
tire community, a plan which is being followed in some cases. A
pound of seed may be separated in less than half an hour. Thus it
is seen that the apparatus and cost of operating are very small and
not sufficient to prevent any tobacco grower from eliminating all
heht and poorly developed seed, in this way not only increasing
the yield, but also improving the uniformity and quality of his crop.
DISEASE RESISTANCE.
In practically all fields producing diseased tobacco plants where the
writers have made observations some degree of immunity has been
noticed in individual plants which have been found growing among.
badly diseased plants on infected soil. These cases of immunity could
not be explained on the ground of any differences in treatment, but
their resistance to disease was evidently inherent in the individual
plants. The same conditions have been found by other investigators
and workers in other farm crops, and from these resistant individuals
many unmunhe strains have been developed. Among the most notable
are the variety of wilt-resistant cotton, improved by Mr. W. A.
Orton and Mr. Rivers, and the Iron cowpea, which is resistant to
root-knot caused by nematodes, improved by Dr. H. J. Webber and
Mr. W. A. Orton. The transmission of this immunity found in indi-
vidual plants has made it possible to develop immune strains, and in
that way to produce thoroly healthy crops on disease-infected soils.
In most cases where immune plants occur, if seed is saved from a
large number of such plants some of them will be found to transmit
their resistance to the progeny uniformly and thus give rise to the
easiest known method for the control of certain plant diseases.
In the case of tobacco, the seed of the immune plants must be saved,
with precautions to avoid cross-pollination, to insure the best results.
In the season of 1903 the writers made selections of plants in several
tobacco fields in the Connecticut Valley which showed immunity to
the tobacco wilt. These plants stood out very plainly and strikingly
in the diseased sections of the field, making a normal growth, and
were apparently not affected by the wilt in any way, while plants
growing all around them were so badly diseased that they produced
no tobacco, and many of them died before maturing seed. Seed was
also saved from some of the diseased plants that reached maturity.
Two rows were planted the following year on the infected soil, one
from seed of a resistant plant and the other from seed of an immune
plant, with the results shown in Plate LX, figure 2. In this instance,
by reason of the foregoing and other observations, it was found that
complete resistance to the wilt was obtained by one year’s selection.
96
DISEASE RESISTANCE. 61
A wilt in tobacco occurs in North Carolina which is evidently a
parallel case with the one found in Connecticut, and in all probability
could be controlled in the same way.
One of the most serious diseases affecting tobacco at present is the
root-knot caused by nematode worms. ‘Tobacco seems to be particu-
larly susceptible to the attacks of nematodes, and many crops are
more or less seriously affected by this enemy. There is no known
remedy for this pest that 1s applicable in a practical way to field con-
ditions. Soil-sterilization methods are used successfully in plant
beds or in greenhouses, but such treatment is rather too expensive
to be used on large fields. The most practicable method for the con-
trol of this disease seems to be in the way of securing immune strains
of tobacco by seed selection and breeding. The writers have se-
lected a large number of individual plants that showed immunity in
the field, and the seed of these selections will serve as a basis for ex-
periments in the production of nematode-resistant types. The com-
plete success of other workers in obtaining resistance to nematodes
im varieties of sugar beets and cowpeas is good evidence that similar
results may be obtained in their efforts to obtain resistance to this
enemy in tobacco. The [ron cowpea shows strong resistance to the
nematode when planted on badly infected tobacco fields, and for this
reason can be highly recommended to tobacco growers for use in
this connection.
The mosaic disease causes very serious injury in tobacco fields in
many parts of this country. The writers believe, from indications
observed during the past two years, that it will be possible to develop
strong, vigorous strains of tobacco which will be largely resistant
to this disease. In the case of some Maryland selections, resistance
to the mosaic disease seems to have been transmitted in a large
degree to the progeny of certain vigorous strains. In two plats
grown side by side under uniform conditions, one from seed of a
parent plant affected with mosaic disease, the other from a perfectly
healthy one, the following results were obtained: Plat 1, grown from
the seed of the mosaic plant, showed 80 per cent of diseased plants
in the field; plat 2, grown from the seed of a perfectly healthy plant,
showed less than 20 per cent of diseased plants. It maybe impos-
sible to entirely eradicate this disease by the production of immune
varieties, owing to the peculiar nature of the malady, but these fig-
ures, which have been duplicated many times, show very conclusively
that by the development of stronger and hardier types of tobacco,
especially where heavy seed is used for sowing, it will be possible to
gradually reduce the percentage of mosaic plants in ordinary to-
bacco fields.
96
62
TOBACCO BREEDING.
There are numerous tobacco diseases which the writers believe may
be largely eradicated by producing immune strains. It is the inten-
tion of the Office of Plant Breeding Investigations to take up work
with as many of these diseases as seems practicable and endeavor
by selection to produce resistant types wherever it is possible to do so.
A NEW VARIETY PRODUCED BY
SEED SELECTION.
UNCLE SAM SUMATRA.
The original plants from which the
variety of tobacco known as Uncle
Sam Sumatra has been produced by
seed selection were grown under shade
on the plantation of the Connecticut
Tobacco Corporation, near Tariffville,
Conn. The first selections were made
in the season of 1903 on this planta-
tion in a field the plants of which were
grown from seed originally brought
from Florida. The Florida seed was
produced by plants which were grown
from seed originally imported from
the island of Sumatra. In a careful
study of the Connecticut-grown Su-
matra crops in 1903 a number of dis-
tinct types were discovered, some of
which were evidently very undesira-
ble, while others were apparently
desirable.
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