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The Rural Science Series
EpItep sy L. H. BAILEY
PLANT-BREEDING
The Wural Science Series
Tue Sor. Hing.
Tur SprayYING OF Pruants. Lodeman.
MILK AND ITs Propucts. Wing. Enlarged and Revised.
Tue FertTILITy OF THE LAND. Roberts.
Tue PrincreLes OF Fruit-crowinc. Bailey. 20th
Edition, Revised.
Busn-Fruits. Card.
FerTILIzZERS. Voorhees.
THe PRINCIPLES OF AGRICULTURE. Bailey. 15th Edition,
Revised.
IRRIGATION AND DRAINAGE. Sing.
Tue FarmstHEAp. Roberts.
Ruravt WeattTH AND WELFARE. Fairchild.
THE PRINCIPLES OF VEGETABLE-GARDENING. Bailey.
Farm Pouttry. Watson. Enlarged and Revised.
Tue Freepinc oF ANIMALS. Jordan.
THe FarMer’s Bustness Hanpsook. Roberts.
Tue Diseases OF ANIMALS. Mayo.
Tue Horse. Loberts.
How to CHoosE A Farm. Hunt.
ForaGeE Crops. Voorhees.
BACTERIA IN RELATION TO CountTRY LiFe. Lipman.
Tue Nursery-Book. Bailey.
PLANT-BREEDING. Bailey and Gilbert. Revised.
Tue Forcine-pook. Bailey.
THe Prunine-Book. bailey.
FRUIT-GROWING IN ARID ReGions. Paddock and Whipple.
Rurat HyGiEne. Ogden.
Dry-FARMING. Widésoe.
Law FOR THE AMERICAN FARMER. (Green.
Farm Boys anp Girits. McKeever.
Tue TRAINING AND BREAKING OF Horses. Harper.
SHEEP-FARMING IN NortH AMERICA. Craig.
CoOPERATION IN AGRICULTURE. Powell.
Tue Farm Woop.ot. Cheyney and Wentling.
HovusenHoip Insects. Herrick.
PLANT-BREEDING
| BY;
3
AILEY
| abd be
NEW EDITION REVISED BY
ARTHUR W.GILBERT, Pu.D.
PROFESSOR OF PLANT-BREEDING IN THE NEW YORK
STATE COLLEGE OF AGRICULTURE AT
CORNELL UNIVERSITY
New Work
THE MACMILLAN COMPANY
1915
All rights reserved
CopyrRiaHtT, 1895, 1906,
By L. H. BAILEY.
Set up and electrotyped. Published December, 1895. Reprinted
April, 1896; August, October, 1897; March, 1902; March, 1904.
Fourth edition, with additions, April, 1906; April, 1907; July,
1908; August, 1910; February, 1912; October, 1913.
New ReEvIsED EpITION, ENTIRELY RESET.
CopyrigHtT, 1915,
By THE MACMILLAN COMPANY.
Set up and electrotyped. Published February, 1915.
Norwood ¥ress
J. §. Cushing Co. — Berwick & Smith Co.
Norwood, Mass., U.S.A.
K2¢
FEB 11.1915
©cia393605
FA.49 }
‘
HISTORY
Tuis book had its beginning in a lecture that I gave
twenty-three years ago (December 1, 1891) before the Mas-
sachusetts State Board of Agriculture, in Boston, on “ Cross-
Breeding and Hybridizing” ; and this lecture, in turn, was
the outgrowth of one given in 1885 and soon afterwards
published. Under the same title, but with a bibliography
added, the Boston lecture was published as a pamphlet in
1892, and placed on sale, by the Rural Publishing Company
of New York, as one of the Rural Library Series. It com-
prised forty-four pages, and sold for 40 cents. In the sum-
mer of 1895, I gave two addresses on variation and the
origination of domestic varieties of plants under the auspices
of the American Society for the Extension of University
Teaching at the University of Pennsylvania. In the mean-
time, I had been teaching the subject to my classes in
horticulture in Cornell University. In the latter part of
1895, I put together these materials in book form, and hay-
ing no short descriptive title I used the word or compound
“ Plant-Breeding.” Of this work, the Massachusetts leec-
ture comprised Chapter II, and the Philadelphia lectures
Chapters I and III. The bibliography was not included.
Chapter IV comprised “ Borrowed opinions” from the
writings of Verlot, Carriere, and Focke. Carriére’s work
on “Production et Fixation des Variétes dans les Vege-
taux” had been translated, with a view to publication, as
early as 1886. The book, “ Plant-Breeding,” was translated
V
vl History
into the French by J. M. and E. Harraca, and published in
Paris in 1901 as “ La Production des Plantes.”
Having been thrice reprinted, the second edition was
issued in 1902, although, through an inadvertence, it was
not so marked on the title-page. Few text-changes were
made, but the bibliography was included.
Early in 1904 the third edition was issued. The bibli-
ography was extended, and some changes were made in the
text; but the principal departure was a new Chapter IV,
from which the old “ Borrowed opinions” were omitted,
and “Recent opinions” were substituted, comprising a dis-
cussion of the work of de Vries, Mendel, and others, and
a statement of the current tendencies of American plant-
breeding practice. “In the eight years since this book was
sent to the printer,” it was stated in the preface to the third
edition, “there have been great changes in our attitude
toward most of the fundamental questions that are dis-
cussed in its pages. In fact, these years may be said to
have marked a transition between two habits of thought in
respect to the means of the evolution of plants, — from the
points of view held by Darwin and the older writers to
those arising from definite experimental studies in species
and varieties. We have not given up the old nor wholly
accepted the new, but it is certain that our outlook is shift-—
ing. So far as practical plant-breeding is involved, the
changing attitude is concerned chiefly with discussions of
the nature of varieties and the nature of hybridization.”
It was declared that ‘the time cannot be far distant when
the subject of plant-breeding will be rewritten from a new
point of view.”
In 1906, the fourth edition appeared, with a new chapter
on “Current plant-breeding practice”; and the book had
History vil
grown from the 293 pages of the original edition to 483
pages. This edition was translated into the Japanese by
D. Karashima, and published in 1907.
We now come to the present edition. The book has been
made over by Dr. Gilbert, who has rewritten some of it
and who has added all the new material, and in whose
hands I have been glad to place it. My work in this
edition has been only editorial. A considerable part of the
old work has been preserved, whether wisely or not will
be the occasion for different opinions. It has seemed to be
desirable to retain something of a former point of view
while at the same time expressing the applications of the
work in the method and the language of the day. Con-
siderable use has been made of the work of others, as is
apparent in the pages. The Open Court Publishing Com-
pany has loaned illustrations from the important work of
de Vries, and pictures have been taken from the Yearbooks
of the United States Department of Agriculture. All these
aids we are glad to acknowledge.
These new investigations have taken us far from the
point of view of Darwin, in which the original editions of
the book were founded. I doubt whether the students
receiving their instruction to-day, with all their abounding
facilities and opportunities, have any such feeling for a
master-spirit as we had in those days when the studies of
Darwin had given a new meaning to nature, when there
were still a few naturalists left, and when the glow of his
writings was warm in every person’s work. To one coming
out of a plant-growing relationship, the masterful works of
Darwin had introduced order, and the forms of cultivated
plants had been made worthy of serious study. This inter-
est was further stimulated by the writings of Wallace and
Vill History
others. All these writings were fascinating to read. How
to produce new forms of vegetation seized some of us with
irresistible power. The literature has now become complex
and difficult, with considerable gain, no doubt, in a closer
acquaintance with the subject, and a nearer approach to the
ultimate truth; but the charm of the simple literature is
largely buried, and I fear that much of our interest is now
expressed in the discussion of methods and in disputing
about the reasons. Yet we are accumulating knowledge,
and after a time we shall come back to clarity and to a
simplicity that the layman can use.
LH. BAILEY:
IruAca’,. Ni Y,
December 1, 1914.
TABLE OF CONTENTS
CHAPTER I
PAGES
THe Fact AND PHILOSOPHY OF VARIATION ; ; ; 1-138
The fact of individuality, 2— variation and adapta-
tion, 7 — species-formation, 8 — conception of unit char-
acters, 9 — differences between plants and animals with
regard to general association of parts and their methods
of reproduction, 10 — bud-variation and bud-varieties, 11.
CHAPTER II
THe Causes oF INDIVIDUAL DIFFERENCES . : : ‘ 13-30
Fortuitous variation, 14— action of natural selection
on variation, 14—sex as a factor in the variation of
plants, 15 — physical environment and variation, 16—
do external influences produce permanent effects in
plants, 17 — natal and post-natal variations, 18 —con-
ception of biotypes, 19— variation in food supply, 20
—variation in climate, 22—food supply in different
branches, 23 — what cultivation is, 24 — variation in cli-
mate, 25 — man’s control over climate as a means of
making plants vary, 27——change of seed, 28 — bud-
variation, 29 — struggle for life a cause of variation, 30.
CHAPTER III
THe CHOICE AND FIxaTION OF VARIATIONS : . ; 34-40
What is a variety, 35 —adaptation in nature, 87 —
artificial selection, 37—bud selection, 39 — variation
and selection not entirely within man’s control, 39.
ix
x Table of Contents
CHAPTER IV
PAGES
THE MEASUREMENT OF VARIATION. : : : E 41-51
The science of biometry, 41 — type, 48 — biometrical
expression of variability, 43— mode, 44 — modal coefti-
cient, 45— mean, 45—use of mean, 46 — mathematical
expression of variability, 47 — average deviation, 47 —
standard deviation, 48 — coefficient of variability, 49 —
probable error, 50 — use of statistical methods, 51.
CHAPTER: V
MutTATIONS . : : : : ; ‘ : : 52-91
Evolutionary theories of Darwin and de Vries, 52 —
differences between fluctuating variations and mutations,
54 —history of mutation, 55—history of the appear-
ance of double flowers, 56 — de Vries’ experiment with
cenotheras, 59— analytical table of seedlings (after de
Vries), 68 — how the mutants were produced in the gar-
den, 71— mutating strains of O. Lamarkiana, 72 — de
Vries’ laws of mutability of the evening-primroses, 72 —
frequency of occurrence of mutations, 79 — spontaneous
occurrence of new elementary species in the wild state,
80 — spontaneous occurrence of new elementary species
and varieties under cultivation, 80 — experimental study
of the origin of mutations, 84— experiments in the pro-
duction of double flowers, 86— what do new characters
come from, 90 — can mutations be produced artificially,
90 — economic significance of mutations, 90.
CHAPTER VI
THE PHILOSOPHY OF THE CROSSING OF PLANTS, CONSIDERED
IN REFERENCE TO THEIR IMPROVEMENT UNDER
CULTIVATION . : : : d a , ; 92-148
The struggle for life, 92— survival of the most fit, 98
— flexibility as an aid to survival, 93 — causes of varia-
bility, 94— origin and function of sex, 95 — effects of
Table of Contents
crossing on the species, 97—the limits of crossing, 97
—swamping effects of inter-crossing, 98 — what deter-
mines the limits of crossing, 98 —the limits of crossing
tend to preserve the identity of species, 99 — the refusal
to cross, the result of natural selection, 100—for the
production of useful hybrids, do not have the parents
too diverse, 101 — function of the cross, 101—rarity of
natural hybrids, 102 — change of seed and crossing, 103
—results from change of stock, 105—crossing from
standpoint of plant improvement, 108 — understanding
of terms, 108—history of plant hybrids, 110— what
plants can be hybridized, 111—vigor as a result of
crossing, 112 — Darwin’s experiments with morning-
glories, 114 — Darwin’s results with other plants, 115 —
increased vigor in other crosses, 115 — three factors, 117
—-the outright production of new varieties, 118— how
to overcome antipathy to crossing, 121 — variability of
hybrids, 122 —characteristics of crosses, 128 — difficul-
ties in making successful crosses, 125 — hybridization
and asexual propagation, 125 —in-breeding, 127 — expe-
rience with egg-plants and squashes, 128 — influence of
sex on hybrids, 188— uncertainties of pollination, 140
—graft hybrids, 142-—the case of Cytisus Adami, 142
— Winkler’s Solanum graft-hybrids, 146—are these
real graft-hybrids, 147.
CHAPTER VII
HEREDITY
Heredity studied collectively, 149 — the coefficient of
heredity, 152 — notation, 153 — conception of unit char-
acters, 154— knowledge of heredity has come through
experimental breeding, 154—rediscovery of Mendel’s
work by de Vries and others, 155 — Mendel’s experi-
ments, 157 —explanation of mendelian results, 166 —
explanation of diagram, 171 — Mendel’s results with the
offspring of hybrids in which several differentiating char-
Xl
PAGES
Xl
Table of Contents
acters are associated, 171— Mendel’s iaw of inheritance
of unit characters (table), 175 — results in F) with com-
plete dominance in every character-pair (table 1), 176 —
results involving three pairs of characters (trihybrid),
177 —incomplete dominance, 179—presence and ab-
sence hypothesis, 181— examples of mendelian inherit-
ance due to the presence and absence of a single unit,
181 — mendelian inheritance of color, 185 — white flowers
in F, from red x cream, 187 —the ratio 9:3: 4, 188 —
colored forms from white x white and the 9:7 ratio,
188 — Emerson’s experiments with beans, 189 — absence
factors, 192 — mutations resulting from mendelian segre-
gation and recombination, 195— mutations which men-
delize are constant, 193—mendelism in wheat, 194—
mendelism summarized, 200 — application to plant-
breeding, 202 — the probable limits of mendelism in the
production of new varieties, 204 —conclusion, 208.
CHAPTER VIII
How Domestic VARIETIES ORIGINATE
Indeterminate varieties, 209 — plant-breeding, 212 —
plant-breeding by selection, 218—rules for breeding
plants, 222 — specific examples, 253 — the dewberry and
blackberry, 255 — the apple, 255 — beans, 260 — cannas,
265 —the cabbage family, 267 —the chrysanthemum, 267.
CHAPTER IX
POLLINATION: OR How To Cross PLANTS .
The structure of the flower, 270— manipulating the
flowers, 281.
CHAPTER X
THE ForwaRD MOVEMENT IN PLANT-BREEDING .
Systematic improvement of plants, 295—the plant-
breeder should aim toward definite ideals, 297 — plant
PAGES
209-269
270-293
294-323
Table of Contents
improvement a serious business, 298—the results of
plant-breeding effort, 299 —state plant-breeding associ-
ations, 300— other plant-breeding associations, 304 —
commercial breeding agencies, 308 — work of the council
of grain exchanges, 310— United States Department of
Agriculture and state experiment stations, 310 — work
of the state agricultural experiment stations, 314 —in-
struction in plant-breeding in the United States, 321 —
Luther Burbank, 321.
APPENDIX A
GLOSSARY OF TECHNICAL PLANT-BREEDING TERMS ,
APPENDIX B
PLANT-BREEDING Books
APPENDIX C
List OF PERIODICALS CONTAINING BREEDING LITERATURE
APPENDIX D
BIBLIOGRAPHY
APPENDIX E
LABORATORY EXERCISES : : : ,
Exercise 1 — Field study of variations by abs an
herbarium of variations .
Exercise 2— The statistical seks of. lees aa
variability
Exercise 3 — Eaeesittign
Exercise 4— Statistical study of pares fiden different
trees
Exercise 5 — “Statistical eee of Teepiesies at different
trees
xill
PAGES
325-327
328-31
302-554
335-393
394-467
394-399
399-412
412-420
420
420-423
X1V
Table of Contents
Exercise 6 — Statistical study of the quantity of grapes
from different grape vines
Exercise 7 — Study of VantiOn in rested specimens
of ragweed or some plant showing many different types
Exercise 8 — Study of bud variation and reversions in
ferns
Exercise os Study of he morphology of different
kinds of flowers
Exercise 10— "Technigue of ches cross- pnlhuation of
plants
Exercise 11 — Emberolosieal arias front aides shows
ing cell division at different stages, chromosomes, pollen
mother cells, development of the embryo sac, etc.
Exercise 12— Study of pollen germination and
fecundation i
Exercise 13 = Practiced in the cross- pollinanon of ap-
ples, pears, peaches, plums, etc. ; :
Exercise 14 — Studies of mendelian inherifante
Exercise 15— A study of mendelian characters in
timothy and oats
Exercise 16 — Mendelian neoblewie
Exercise 17 — Ear-to-row test with corn
Exercise 18 — Corn judging
Exercise 19 — Statistical study of ears ‘of corn
Exercise Tee of correlations of characters in
corn
Exercise 21 — Gore poccian a iaborene ste
Exercise 22 — A study in potato selection .
Exercise 23 — Study of citrus hybrids :
Exercise 24 — Study of the results of the plant- sono
tests of wheat, oats, cabbage, onions, or any crop where
data are available ; ‘ é
Exercise 25 — Studies of en of baeties come
wheat, apples, plums, grapes, etc.
Exercise 26 — Field trip to experimental Seale
Exercise 27 — Working plans for practical breeding
experiments
PAGES
425
423
425-424
424-426
426-428
428
428
429
429-435
435-438
438-445
445-447
447-448
448-449
449-450
450-452
452-457
457-458
458
458
458-459
459
LIST OF ILLUSTRATIONS
FIGURE
1. Variation in heads of timothy
2. Two seedling timothy plants, growing side iF sie sowie
a common kind and degree of difference
3. A productive timothy plant .
4, A timothy plant that runs much to seed ;
5. A timothy plant that runs almost wholly to leaf .
6. Couch or quack grass, showing means of asexual propaga-
tion by underground root stalks
7. Orange hawkweed
8. A frequency curve illustrating the distr ibasion of the height
of the pea plants
9. Variations in statures of Gingihera dejiella, tant aa
Hnothera Lamarkiana, its parent .
10. Variations in the amount of sugar in 40,000 beets
11. Chelidonium majus
12. Chelidoniwm laciniatum
3. Anemone coronaria, piele™naieanad ford
14. Anemone coronaria, semi-double-flowered form
15. Anemone coronaria var. florepleno
16. Hugo de Vries
17. nothera Lamarkiana ated Gnoihera RenciiG in Bas
18. Gnothera Lamarkiana. Curve exhibiting variations in the
length of fruits of 568 plants .
19. nothera lata —@nothera Lamarkiana epectheta dante
20. A, spike with almost ripe fruits of Hnothera gigas, a mutant
species; B, the same of (nothera Lamarkiana, its
parent form
21. The cage in Professor de vevies? Benetinent Sanien: pWorinl
corn and various species of Gnothera
XV
53
63
66
XVl1 List of Illustrations
FIGURE
22. Cupid sweet pea (photo by Beal) .
23. Linaria vulgaris — peloric flowers
24. Linaria vulgaris peloria
25. Antirrhinum majus :
26. Chrysanthemum segetum pishin :
27. Chrysanthemum inodorum plenissimum : :
28. Ancestral generations of Chrysanthemum segetum plenum
29. A, Chrysanthemum segetum; B, Chrysanthemum segetum
grandiforium (after purification) . :
30. Extreme variability in the shape of the leaves of hy brid pop-
pies. Second generation from a cross between the Bride
variety of the Opium poppy and the Oriental poppy
31. Inbred corn plants, showing lessened vigor of growth
(adapted from Yearbook)
32. Hybrid walnut and parents
33. A hybrid walnut (Juglans californica fenay: ronenag
double the height of ordinary trees
34. Variation in hybrid pineapples
35. Variation in hybrid squashes
36. Hybrid citrange and its parents, Pantivis er a) trifoliata
and common sweet orange :
37. Hybrid tangelo and its parents, pomelo and baer ine).
58. Samson tangelo (adapted from Yearbook)
59. Citranges (hybrid of orange and Poncirus (citrus) trifoliata)
40. Teosinte and its hybrids with Indian corn ‘ ,
41. Cytisus Adami
42. Cytisus Adami
43. Mendelism in maize
44. Diagrammatic See Peer of Mendel's ES
45. Hybrid carnation between a single and a burster, sub wine
intermediacy .
46. Fowls’ combs ;
47. Three generations of hybrid ores
48. Mendelism in tomatoes . :
_49. Pride of Georgia, a good short- eanie eoitane
50. Select Jones improved cotton with uniform long Reale
51. Improving the tomato
List of Illustrations XVll
FIGURE PAGE
52. Crop averages in corn breeding for high and for low protein.
Results of twelve generations. (Ill. Exp. Sta.) . . 216
53. Fruit of wild elderberry : ; ou
54. Fruit of a cultivated variety of the Siterberes ‘yetaael ap-
peared as a variation from the wild form ‘ 218
55. Field of wilt-resistant watermelons, growing free from diac
on infected land (from tae : ; . . 219
56. Disease resistance in cowpeas : 220
57. Improved types of lettuce and the varieties Poi which ace
were developed ; E ‘ : : ; é $i 2St
58. Wild cabbage : . : , : : - : .. 240
59. Curled kale . : : : : . : ’ : is AR
60. Collard . ; ; , z é : : : . 22
61. Brussels sprouts. ‘ ; ‘ : ; , ¢ . 248
62. Savoy cabbage 2, a ; : : : : ; . 244
63. Cabbage shapes. ; : : ; . 245
64. Swede turnip, kohl-rabi, and Gaaiiflowe a : ; . 248
65. Wild form of Chrysanthemum morifolium . s ; . 249
66. Wild form of Chrysanthemum indicum : : : . 250
67. Pompon anemone type . i ; 2 ; 3 : . 251
68. Single type . : ‘ ; i ; ; . 252
69. Type of pompon ahepeecatheriain ; : : : . . 253
70. Japanese anemone type P : ! : , ‘ . 256
71. The small and regular anemone type . : ‘ , a ee
72. A pompon chrysanthemum . : : , : . 258
73. Type of Japanese incurved chry Sausthocaiin . 259
74. Japanese anemone chrysanthemum when fully See less . 262
75. New type with short stem . : ! 2 : : . 263
76. Incurved type : é Z : A 3 : q . 264
((.. Hairy type. . é : : 2 : : : : . 267
78. Japanese type . ; : : é ; ’ . . 268
79. Reflexed type : ‘ : : : ‘ : . 269
80. Bellflower . : ‘ . : : : ; . 270
81. Flower of white lily : , 4 : ; , ees fi
82. Flower of greenhouse Se odbetiaia : ‘ f : . 272
83. Flower of night-blooming cereus . : F . > 28
84. Flower of the shrubby hibiscus ( Hibiscus nia ‘ . 204
XV List of Illustrations
FIGURE
85. Bugbane (Cimicifuga racemosa)
86. Blossom of flowering raspberry (Rubus baa
87. Squash flowers of each sex .
88. Flowers of clematis (Clematis ainiiana’.
89. Tobacco flowers, showing the parts of the flower, a paul
ready to be emasculated, and an emasculated subject .
90. Zinnia flowers
91. Instruments used in aallnntine flow ers
92. Ladle for pollinating house tomatoes
93. Bag for covering the flowers
94. Fuchsias, showing the stamens and nistila, Goa a ‘Gall feaay
to be emasculated .
95. Fuchsia flower emasculated
96. Fuchsia flower tied up after emasculation
97. Tomato and quince
98. Pollinating kit
99. Pollinating kit
100. Main building of Seed icentantion: aiices of Sw edish Cae
pany (photo by Newman)
101. Gardens at Luther Burbank’s :
102. Some of Burbank’s frames and garden hada
105. Spineless and spine-bearing cacti at Burbank’s :
104. A specimen herbarium sheet, showing variations in the
leaves of the mulberry . ‘
105. A specimen herbarium sheet, showing dimerence hare een
two leaves of the horse radish
106. A specimen herbarium sheet, showing variations in eaves
of the Persian lilac
107. A specimen herbarium sheet, aaae ea ntnine in ewer
of the blackberry .
108. A common form of ragweed
109. Another form of ragweed
110. Demonstration of allelomorphism and of EGninleks Aatataiee
111. Demonstration of presence and absence hypothesis and of
intermediacy . A :
112.. Demonstration of the presence oe an inhibitor rabie :
Explanation of so-called ‘‘dominance and absence”’ .
The Rural Science Series
EpItTep By L. H. BAILEY
PLANT-BREEDING
venti
Pas <5"
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PLANT-BREEDING
CHAPTHe I
THE FACT AND PHILOSOPHY OF VARIATION
THERE is no one fact connected with agriculture that
more greatly interests all persons than the existence of
numerous varieties of plants that seem to satisfy every need
of the gardener. Whence came all this multitude of
forms? What are the methods employed in securing
them’? Are they merely isolated facts or phenomena
of gardening, or have they some relation to the broader
phases of the evolution of the forms of life? These are
some of the questions that occur to every reflective
mind when it contemplates an attractive garden, but
they are questions that seem never to be answered.
Whatever attempt the gardener may make at answer-
ing them is either obscured by an effort to define what
a variety is, or else it consists in simply reciting how a
few given varieties came to be known. But there must
be some method of arriving at a conception of the ways
whereby the varieties of fruits and flowers and other culti-
vated plants have originated. If there is no such method,
then the origination of these varieties must follow no
law, and the discussion of the whole subject is fruitless.
But we have every confidence in the consecutive uniform-
B 1
2 Plant-Breeding
ity of the operations of nature, and it were strange if
some underlying principle of the unfolding or progression
of plant-life does not dominate the origin of the varied
and innumerable varieties which, from time unknown,
have responded to the touch of the cultivator. Let us
first, therefore, make a broad survey of the subject in
a philosophical spirit, and later, discuss the more specific
instances of the origination of varieties.
The fact of individuality. — There is universal difference
in nature. No two living things are counterparts, for no
two are born alike or into exactly the same conditions and
experiences. Every living object has individuality; that
is, there is something about it that enables the acute
observer to distinguish it from all other objects, even of
the same class or species. Every plant in a row of lettuce
is different from every other plant, and the gardener,
when transplanting them, selects out, almost uncon-
sciously, some plants that please him and others that do
not. Every apple tree in an orchard of a thousand
Baldwins is unlike every other one, perhaps in size or
shape, or possibly in the vigor of growth or the kind of
fruit it bears. Persons who buy apples for export know
that fruit from certain regions stands the shipments better
than the same variety from other regions ; and if one were
to go into the orchards where these apples are grown, he
would find the owner still further refining the problem by
talking about the merits of individual trees in his orchard.
If one were to make the effort, he would find that it is
possible to distinguish differences between every two
spears of grass in a meadow, or every two heads of wheat
in a grain-field.,
The Fact and Philosophy of Variation 3
In timothy, one of the commonest of our grasses, a
casual observer may find differences in the length, shape,
and color of heads; tendency of some plants to produce
asexual leaves in the head; form of base of the head;
My
ft kn
Seay
iene
.
af Ate,
wage
Ce
x
i
*, *
Fic. 1. — Variation in heads of timothy.
length, width, and color of leaves; erect or drooping
character of the leaves; susceptibility of the leaves and
stems to rust; period of blooming; habit of growth of
plant, — erect or decumbent; few or many culms to the
plant; ability to recover after cutting; quantity of seed
Plant-Breeding
a common kind and degree of difference.
ing
ide, show
le bys
SiC
S
.
, growing
Fic. 2. — Two seedling timothy plants
5
The Fact and Philosophy of Variation
Fic. 3. — A productive timothy plant.
Similar differences
may be found in any group of plantsif the group is suffi-
ciently studied.
1-5).
produced, and others (Figs.
6 Plant-Breeding
Fig. 4. — A timothy plant that runs much to seed.
Variation and adaptation. — All this is equivalent to
saying that plants are infinitely variable. The ultimate
The Fact and Philosophy of Variation 7
causes of all this variation are beyond the purposes of the
present discussion, but it must be evident, to the reflective
mind, that these differences are a means of adapting
the innumerable individuals to every little difference or
Fic. 5. —A timothy plant that runs almost wholly to leaf.
advantage in the environment in which they live. And
if the result of variation is better adaption to the physical
conditions of life, then the same forces must have been
present in the circumstances which determined the birth
of the individual. This change in environment may be
8 Plant-Breeding
the cause of much of the variation in plants, since differ-
ences in plants were positively injurious if it were possible
for the conditions of environment to be the same.
Species-formation. —If no two plants are anywhere
alike, then it is not strange if now and then some de-
‘parture, more marked than common, isnamed and becomes
a garden variety. We have been taught to feel that
plants are essentially stable and inelastic, and that any
departure from the type is an exception and calls for im-
mediate explanation. The fact is, however, that plants
are essentially unstable and plastic, and that variation
between the individuals must everywhere be expected.
This erroneous notion of the stability of organisms comes
of our habit of studying what we call species. We set
for ourselves a type of plant or animal, and group about it
all those individuals that are more like this type than
they are like any other, and this group we name a species.
Nowadays, the species is regarded as nothing more than a
convenient and arbitrary expression for classifying our
knowledge of the forms of life, but the older naturalists
conceived that the species is the real entity or unit in
nature, and we have not yet wholly outgrown the habit of
mind which was born of that fallacy. Nature knows
little about species; she is concerned with the individual,
the ultimate complete and working unit. This individual
she molds and fits into the opportunities of environment,
and each individual tends to become the more unlike its
birthmates the more the environments of the various in-
dividuals are unlike.
We must consider, therefore, as a fundamental concep-
tion to the discussion of the general subject before us, the
The Fact and Philosophy of Variation 9
importance of the individual plant, rather than the im-
portance of the species; for thereby we put ourselves as
nearly as possible in sympathetic attitude with nature, and,
resting upon the ultimate object of her concern, we are
able to understand what may be conceived to be her motive
in working out the problem of life: Recall the fact that
the whole tendency of contemporary civilization, in soci-
ology and religion, is to deal with the individual person
and not with the mass. The present-day method of study-
ing the evolution of plants and animals is essentially an-
alytical. As the chemist attempts to discover the smallest
units from which the substances of nature have been built
up, so the student of biology and evolution is seeking for
the smallest heritable units of which plants and animals
are composed. This is only an unconscious feeling after
natural methods of solving the most complex of problems,
for it is exactly the means to which every organic thing
has been subjected from the beginning.
Conception of unit-characters.— The student of evolution
now conceives animals and plants to be composed of what
he terms “unit-characters,” analogous, roughly, to the
atoms of the chemist. These are the smallest heritable
units that a plant or animal may possess. Any distinct
entity that can be traced from one generation to another,
such as the presence or absence of pubescence on the leaves
or stems, the height of the plant, whether dwarf or tall,
the color of the flower or fruits, and very many others are
now known as unit-characters. The more any group of
plants is studied, the more definite and distinct these
unit-characters become. The time may come when the
gardener, from long experience, shall become acquainted
10 Plant-Breeding
with these qualities, so that he may synthetically put
many units together by crossing and produce new varieties
_almost at will.
Differences between plants and animals with regard to
general association of parts and their methods of reproduction.
— Unit-characters are nature’s blocks, which she uses to
build up plants and animals into various shapes for dif-
ferent purposes. These combinations of units when
added together in proper extent and proportion consti-
tute the plant and animal as we know it, the ultimate
living and working organism, with power of growth and
reproduction.
In looking for the ultimate working unit, individuality or
personality in nature, we must make a broad distinction
between the animal and the plant. Every higher animal
is itself a working unit; it is one. It has a more or less
definite span of life, and every part and organ contributes
a certain indispensable part to the life and personality.
of the organism. No part is capable of propagating itself
independently of the sex-organs of the animal, nor is it
capable of developing sex-organs of its own. If any part
is removed, the animal is maimed and perhaps it dies.
The plant, on the contrary, has no definite or distinct
autonomy. Most plants live an indefinite existence,
dependent very closely upon the immediate conditions in
which they grow. Every part or branch of the plant lives
largely for itself, it is capable of propagating and multi-
plying itself when removed from the parent or the colony
of branches of which it is a member, and it develops sex-
organs and other individual features of its own. If any
branch is removed, the tree or plant does not necessarily
The Fact and Philosophy of Variation 11
suffer; in fact, the remaining branches usually profit
by the removal, a fact which shows that there is a competi-
tion, or struggle for existence, between the different
branches or elements of the plant. The whole theory and
practice of pruning rests upon the fact of the individual
unlikenesses of the branches; and the unlikenesses are of
the same kind and often of the same degree as those that
exist between different plants grown from seeds.
Bud-variation and bud-varieties. —'The branches of a
Crawford peach tree, for example, differ amongst them-
selves-in size, shape, vigor, productiveness, and season
of maturity, much the same as any two or more separate
Crawford trees, or any number of trees of other varieties,
differ the one from the others. If any one of these
branches or buds is removed and is grown into an inde-
pendent tree, a person could not tell — if he were ignorant
of its history — whether this tree were derived from a
branch or a seed. This proves that there is no essential
unlikeness between branches and independent plants, ex-
cept the mere accident that one grows upon another branch
or plant whilst the other grows in the ground. But the
branch may be severed and grown in the ground, and the
seedling may be pulled up and grafted on the tree, and no
one can distinguish the different origins of the two. And
then, as a matter of fact, a very large proportion of our culti-
vated plants are not distinct plants at all, in the sense of
being different creations from seeds, but are simply the
result of the division of branches of one original plant or
branch. All the fruit trees of any one variety are obtained
from the dividing up and multiplication of the branches of
the first or original tree.
12 Plant-Breeding
The reader is curious to know how this original tree came
to be, and this we may find out before we are done; but
for the present, let it be said that it is equally possible for
it to have come from a seed, or to have sprung from a
branch which some person had noticed to be very dif-
ferent from the associated branches in the tree-top. In
other words, the ultimate unit or individual of variation
is the bud and the bit of wood or tissue to which it is
attached; for every bud, like every seed, produces an
offspring that can be distinguished from every other
offspring whatsoever.
CHAPTER II
THE CAUSES OF INDIVIDUAL DIFFERENCES
WE have now gone back to the starting-point, to that
unit with which nature begins to make her initial differ-
ences or individualities ; that is, to the point where varia-
tions arise. This point is the bud and the seed, — one
sexless, or the offspring of one parent; the other sexual,
or the offspring of two parents. Now, inasmuch as the
horticultural variety is only a well-marked variation which
the gardener has chanced to notice and to propagate, it
follows that the only logical method of determining how
garden varieties originate is to discover the means by
which plants in general vary or differ one from another.
There is probably no one fact of organic nature concern-
ing the origin of which modern philosophers are so much
divided as the causes or reasons for the beginnings of
variations or differences. It seems to be an inscrutable
problem, and it would be useless, therefore, for us to
attempt to discover these ultimate forces in the present
book. Still, we must give them sufficient thought to
enable us to satisfy our minds as to how far these variations
may be produced by man; and, in doing this, we must
discover at least the underlying philosophy of plant
variation. It is the nature of organisms to be unlike
their parents and their birthmates. Why?
13
14 Plant-Breeding
Fortuitous variation. — It will probably never be pos-
sible to refer every variation to a distinct cause, for it is
probable that some of them have no antecedent. If we
conceive of the forms of life as having been created with
characters exactly uniform from generation to generation,
then we should be led to look for a distinct occasion or
cause for every departure from the type; but we know, as
has already been pointed out, that heredity by its very
nature is not so exact as to carry over every attribute, and
no other, of the parent to the offspring. Plasticity is a
part of the essential constitution of all organic beings.
There is perhaps no inherent tendency in organisms
towards any ultimate or predetermined completion of
forms, as the older naturalists supposed, but simply a
laxity or indefiniteness of constitution which is expressed in
numberless minor differences in individuals.
That is, some variation may be simply fortuitous, an
inevitable result of the inherent plasticity of organisms,
and it may have no immediate inciting cause.
Action of natural selection on variation. — If we were to
assume that every minor difference is the result of some
immediate cause, then we should expect every individual
plant or animal to fill some niche, to satisfy some need, to
produce the definite effect for which the cause stands.
But it is apparent to one who contemplates the operations
of nature that very many — certainly more than half — of
the organisms which are born are not useful to the per-
petuity of the species and very soon perish. From these
fortuitous variations nature selects, to be sure, many
individuals to be the parents of other generations because
they chance to be fitted to live, but this does not affect
The Causes of Individual Differences 15
the methods or reasons of their origin. It is possible that,
whilst many of these mere individual differences have no
direct and immediate cause, they may still be the result of
-a devious line of antecedent causes long since so much
diffused and modified that they will remain forever un-
recognizable; but even so, the fact still remains that
these present differences or variations may be purposeless,
and it is quite as well to say that they exist because it is a
part of the organic constitution of living things that un-
like produces unlike.
Sex as a factor in the variation of plants. — All plants
have the faculty, either potential or expressed, of propagat-
ing themselves by means of buds, or asexual parts. This is
obviously the cheapest and most direct possible method
of propagation for many-membered plants, since it re-
quires no special reproductive organization and energy,
and, as only one parent is concerned in it, there is none of
the risk of failure that obtains in any mode of propaga-
tion in which two parents must find each other and form
a union. There must be some reason, therefore, for the
existence of such a costly mechanism as sex aside from
its use as a mere means of propagation.
It may be said that sex exists because it 1s a means of
more rapid multiplication than bud-propagation, but such
is not necessarily the fact. Many plants produce buds as
freely as they produce seeds; and then, if mere multipli-
cation were the only destiny of the plant, bud-production
would no doubt have greatly increased to have met the
demand for new generations. The chief reason for
the existence of sex in the vegetable world seems to be the
need for a constant rejuvenation and modification of the
16 Plant-Breeding
offspring by uniting the features of two individuals into
one. There thus arises from every sexual union a number
of new or different forms from which nature may select
the best, — that is, those best fitted to live in the condi-
tions in which they chance to be placed. But whilst
sex is undoubtedly one of the most potent sources of pres-
ent unlikenesses, it is not necessarily an original cause of
individual differences, since the two parties to any sexual con-
tract must be unlike before they can produce unlike. When
once the initial unlikenesses were established, every new
sexual union must produce new combinations, so that
now, when every new form, from whatever source it
appears, comes into existence, there are other intimately
related forms with which it may cross. This state of
things has existed to a greater or less degree from the
moment sex first appeared, so that the organic world is
now endlessly varied as the result of a most complex
ancestry.
Physical environment and variation. — Every phase and
condition of physical circumstances, which are not ab-
solutely prohibitive of plant life, have plants which thrive in
them. Every soil and climate, every degree of humidity,
hills, swamps, and ponds, — every place is filled with
plants. Even the trunks and branches of trees support
other plants, as epiphytes and parasites. That is, plants
have adapted themselves to every physical environment ;
or, to turn the proposition around, every physical en-
vironment produces adaptive changes in plants. There
are those, like Weismann and his adherents, who contend,
from purely speculative reasons, that these changes do
not become hereditary or permanent until they have in-
~_
The Causes of Individual Differences bri
fluenced a certain physiological substance which is assumed
to reside in the reproductive regions of the organisms,
and that all those changes which have not yet reached
this germ-plasm are, therefore, lost, or die with the or-
ganisms.
Do external influences produce permanent effects in
plants? —It is not necessary to discuss here the intri-
cate arguments in the time-honored controversy of the
permanent inheritance of external modifications. Such
violent modifications as traumatic injury do not affect its
germ cells and are not inherited. But it is the common
experience of gardeners that the modifications of the envi-
ronment of plants, such as changing food supply or changing
seed from one environment to another, produce changes
which eventually become hereditary. Whether these
changes of environment act directly upon the germ-plasm
to produce the change or whether they stimulate a ger-
minal change which was otherwise latent, is a question
which long and patient experimentation must decide.
Certain it is, that plants have gone through a profound
modification and it is easy to believe that environment has
played no little part in these changes.
Weismann teaches that ‘acquired characters,” or those
variations which first appear in the life-time of the indi-
vidual because of the influences of environment, are lost,
because they have not yet affected the reproductive sub-
stances ; but if these characters are induced by the effect
of impinging environment during two or more generations,
they may come to be so persistent that the plant cannot
throw them off, and they become, thereby, a part of the
hereditary and non-negotiable property of the species.
Cc
18 Plant-Breeding
Now, it is apparent that in one or another of the genera-
tions which are thus acted upon by the environment, there
must be a beginning towards the fixing or hereditable
permanency of the new forms, and we might as well
assume that this beginning takes place in the first genera-
tion as in the last, since there can be no proof that it does
not take place in either one. The tendency towards
fixity, if it exists at all, undoubtedly originates at the very
time that the variation itself originates, and it is only
sophistry to assume that the form appears at one time
and the tendency towards permanency at another time.
Since plants fit themselves into their circumstances by
means of adaptive variations, we must conclude that all
adaptive variations have the power of persisting, upon
occasion.
All these remarks, whilst somewhat abstruse, have a
most important bearing on the philosophy of the origin
of garden varieties, because they show, first that changes
in the conditions in which plants grow introduce modifi-
cations in the plants themselves, and second, that wher-
ever any modification occurs it is probable that it may
be fixed and perpetuated.
Natal and post-natal variations. — It is necessary at this
point that we distinguish between natal and post-natal
variations, —that is, between those variations which are
born with-plants, and those which appear, as a result of
environment, after the plant has begun to grow. It is
commonly assumed that the form and general characters
of the plant are already determined in the seed, but a
moment’s reflection will show that this is far from the
truth. One may sow a hundred selected peas, for example,
The Causes of Individual Differences 19
all of which may be alike in every discernible character.
If these are planted in a space of a foot apart, it will be
found, after two or three weeks, that some individuals
are outstripping the others, although all of them came up
equally well and were at first practically indistinguishable.
This means that, because of a little advantage in food or
moisture, or other circumstances, some plants have ob-
tained the mastery and are crowding out the less fortunate
ones. The theory and practice of agriculture rests on
the fact that plants can be modified greatly by the condi-
tions in which they grow, after they have become thor-
oughly established in the soil. Plants may start equal,
but differ widely at the harvest; and this difference may
be controlled to a nicety by the cultivator. Every farmer
is confident, also, that the best results for the succeeding
year are to be got only when he selects seeds from the best
that he has been able to produce this year. So, given
uniformity or equality at the start, the operator molds
the individual plants largely at his will.
Conception of biotypes. — Most varieties are not as
uniform as would at first appear. = 4451.8
(SfV) pedtols
n 286
Mean, = 15.5 inches.
Use of mean. — The mean gives a good average value
of the character and is often more useful than the mode
in expressing type. The breeder must use his judgment
The Measurement of Variation 47
as to which should be used in each case, the mean or the
mode.
Mathematical expression of variability. — After the
average or mean of any group of plants has been deter-
mined, it is desirable to know the amount of deviation of
the different individuals from the mean. This determina-
tion gives a concrete expression which is an index of the
amount of variability exhibited. This variability is ex-
pressed as the average deviation or the standard deviation.
The latter is ordinarily employed by mathematicians.
Average deviation. — The average deviation is deter-
mined by obtaining, first of all, the amount which each
class varies from the mean and multiplying each deviation
by the number of individuals concerned. For example,
the column D is obtained by finding the difference between
the mean, 15.5, and the variations in column V: thus
in the first case the difference between 5.8 and 15.5 is — 9.7
while farther down column V we find 16.3, which is greater
than the mean, giving us a value of 0.8 in column D.
Now, if there were the same number of individuals in
each class, the average deviation could be found by adding
up the deviations in column D, and dividing by the total
number of individuals in column f, but there is one indi-
vidual deviating — 9.7 while there are 43 deviating 0.8
and 18 deviating 5.3, and so forth. In order to overcome
this the deviations are multiplied by the number of in-
dividuals giving the column fD. The sum of this column
divided by the total number of individuals gives the
average deviation. This is an index of variability.
The average deviation is expressed by the following
formula : —
48 Plant-Breeding
2 Df.
n
Average deviation =
Standard deviation. — The operations for finding the
standard deviation are the same as for the average devia-
tion except that the deviations in column D are squared
before multiplying by the frequency numbers (f), thus
giving the columns D? and D?f respectively. The sum
of the latter divided by the total number of individuals
and the square root of the result extracted gives the
standard deviation. This can be expressed by the follow-
ing formula : — 5
‘ go 27:
n
The details of determining the average and standard
deviation are as follows : —
V f D {D Diane Df
5.8 i — 9.7 9.70 94.09 94.09
eee 4 — 8.2 32.80 67.24 268.96
8.8 6 — 6.7 40.20 44.89 269.34
10.3 29 es 150.80 27.04 784.16
11.8 30 — 3.7 111.00 13.69 410.70
133) ov — 2.2 81.40 4.84 179.08
14.8 39 — 0.7 27.30 0.49 19.11
16.3 43 0.8 34.40 0.64 25.2
17.8 34 De 78.20 5.29 179.86
19.3 26 3.8 98.80 14.44 375.44
20.8 18 oo 95.40 28.09 505.62
apes 8 6.8 |. 54.40 46.24 369.92
23.8 5 8.3 41.50 68.89 Holt
25.0 Z 9.8 19.60 96.04 192.08
26.8 2 chess 22.60 127.69 200ioo
28.3 il 12.8 12.80 163.84 163.84
29.8 1 14.3 14.30 204.49 204.49
n = 286 925.20 | >=4851.31
The Measurement of Variation 49
Average deviation = —— = 3.24 inches.
Standard deviation, (o) = (ee =
Coefficient of variability. — The average deviation or
standard deviation as outlined above is always determined
in the denomination of the unit in which the plant is
measured ; if it is height of plant in inches, the deviation
will be in inches and so forth. This prohibits the careful
comparison of the deviations of different plants or parts
of a plant because some deviations may be in pounds
or others in inches, and hence they will not be directly
comparable.
It is desirable, therefore, to have an abstract expression
so that the relative amount of variability of one class of
organs may be directly compared with the variability of
another. This is called the coefficient of variability. It is
found by dividing the standard deviation by the mean.
Thus an abstract number is found which expresses the
variability. In our case the standard deviation = 4.1
inches and the mean = 15.5 inches, so that
4.1
Te .264 = 26.4 % = the coefficient of variability.
If the coefficient of variability of the weight of the plants
‘had to be determined and was found to be, say, .384, it
would follow at once that the height of the plant was
considerably more variable than the weight.
The coefficient of variability may be expressed as
follows : —
E
50 Plant-Breeding
Oo
Of uw’ 100.
Probable error.1— It is obvious that these mathematical
expressions of type and variability will be modified some-
what by the number of individuals measured. The
greater the number of individuals employed, the less the
error. These differences which arise from the fewness
of individuals employed is known as the probable error.
It is expressed by a pair of divergences (+ /), the one
above and the other below the actual value found, and
indicates that the chances are even that the true value
lies somewhere between the value found plus the error
and the value minus the error. For example, the probable
error of the mean in the problem here cited is + .016 and
is found by the formula given below. This means that
1 Formule for probable errors : —
Biiene. = Serer as standard deviation ere 67452
n
number of individuals
E standard deviation = + .6745 standard deviation OE
V2 number of individuals
+ .6745
V2n
E coefficient of variability = + .6745 = coefficient of variability
2 X number of individuals
SES (G7/45) ==
V2
But when C is greater than 10% use the formula
EC = + 6745 © [1 ee
Vi2i 100
Nie
The Measurement of Variation ol
the true mean is probably somewhere between 15.5 + .016
and 15.5 — .016 or between 15.516 and 15.484. The size
of the error is generally indicative of the number of the
individuals employed and the general dependability of the
work.
Use of statistical methods. — The use of statistical
methods enables the breeder to express quite accurately
the amount of variability which would otherwise be
expressed with considerable difficulty. It enables him
also to keep an accurate record of his work from year to
year and affords him a convenient method of comparing
one year’s crop with another.
It will be seen later that statistical methods may also be
employed to express correlation and extent of inherit-
ance.
(
CHAR EER
MUTATIONS
THERE is endless dissimilarity in nature. No two
plants and no two animals are exactly alike. There are
more plants and animals than can find a place in which
to live and thrive. There results a struggle for existence.
Those animals or plants which, by virtue of the individual
differences or peculiarities, are best fitted to the condi-
tions in which they are placed, survive in this struggle
for existence. They are “selected to live.” Those that
survive, propagate their peculiarities. By virtue of
continued variation, and of continued selection along a
certain line, the peculiarities may become augmented ;
finally the gulf of separation from the parental stem
becomes great, and what we call a new species has origi-
nated.
Evolutionary theories of Darwin and de Vries. — This,
in epitome, is the philosophy of Darwin in respect to evolu-
tion of organic forms. It contains the well-known postu-
late of natural selection, the principle that we know as
Darwinism. This principle has had more adherents
than any other hypothesis of the process of evolution.
All recent hypotheses in some way relate to it. A number
of them modify it, and some dispute it. The most pro-
nounced counter-hypothesis is also the newest. It is that
52
Mutations 53
of Professor de Vries, botanist, of Amsterdam, Holland,
who denies that natural selection is competent to produce
species, or that organic ascent is the product of small
differences gradually enlarging into great ones. According
to de Vries’ view, species-characters arise suddenly, or
all at once, and they are ordinarily stable from the moment
they arise.
mold
ee ica!
CON
Fic. 9.— Variations in statures of (nothera nanella ee a mutant,
and @nothera Lamarkiana (right), its parent. (£nothera nanella :
Rangel 7—35em.s: Mi. 22.81 = 1 .02\em.s- oa; 7.26 == 0:72 ems: C- V.,
31.84 + 3.16 per cent. Mnothera Lamarkiana: Range, 77—96 cm. ;
Mes 88:68! 1055 em. sor 4.76) 0139 ent C. Vi. o:a0 = 044 per
cent.
5 Za 10-15 16-20 20-25 «26-30 80-35
De Vries conceives that variations, or differences, are of
two general categories: (1) Variations proper, or small,
fluctuating, unstable differences peculiar to the individual
(only partially transmitted to offspring); and (2) muta-
tions, or differences that are usually of marked character,
appear suddenly and without transition to other forms
and are at once the starting-points of new species or races.
Variations proper may be due to the immediate environ-
54 Plant-Breeding
ment in which the plant lives. The mutations arise from
causes yet unknown, although these causes are considered
to be physiological. Probably many so-called mutations
are hybrids and hence not mutations in the strictest
sense.
Differences between fluctuating variations and mutations : —
1. Fluctuating variations are very common and are
to be found in all plants and animals. Mutations occur
intermediately and are rare.
2. Fluctuating variations are thought not to be trans-
mitted. Muta-
tions are trans-
mitted.
3. Fluctuating
variations — pre-
sent a series of
differences which
may be plotted
on a frequency
curve and obey
the laws of
chance. Muta-
tions or saltatory
variations do not
obey the laws of
MS 1 125 13 135 % HS 1S 18S 16 GS 17 125 18 ae chance, and Png
Fig. 10.— Variations in the amount of sugar not be plotted
in 40,000 beets. the form of a
frequency curve.
4. Fluctuating variations do not lead to a new perma-
nent mean of the race. Mutations cause a new mean to be
+A —__
Mutations . 55
formed, around which is grouped a new series of fluctuating
variations, forming a frequency curve. (See Fig. 9.)
5. In a fluctuating variation no new unit characters are
added. The same char-
acters are merely found
in greater or less quan-
tity or number (Fig. 10).
Where a mutation oc-
curs, new unit charac-
ters are added or old
ones lost.
6. Fluctuating vari-
ations represent indi-
viduals or parts of them.
Mutations represent
groups of individuals.
In fluctuating vari-
ations, the small differ-
ences are grouped
around what may be
called a “center of fluc-
tuation,’”’ which is the
mean of the frequency
curve. When a mutation is formed, a new center of
fluctuation is established around a new mean.
History of mutation. — The first mutation was recorded
in 1590. In the garden of Sprenger, an apothecary of
Heidelberg, was found a peculiar form of Chelidoniwm
majus. The new form appeared suddenly and without
intermediates from a lot of plants which had been culti-
vated for many years. This mutant had “leaves cut into
Fic. 11. — Chelidonium majus.
56 Plant-Breeding
narrow lobes with almost linear tips, and the petals were
also cut up.’”’ The new species has been constant since
the first, and follows Mendel’s law when crossed with
C. majus, its par-
ent. (See Figs.
11 and 12.)
The “word
“mutation”’ was
first used in 1650
by Dr. Thomas
Browne, in _ his
book ‘‘ Pseudo-
doxia Epidem-
Vicia: Sino erks
quotes from
Book VI, Chap-
ter. X, “Of ethe
Blackness of Ne-
groes,”’ as fol-
lows :—
“We may say
that men become
black in the same
Fie. 12.— Chelidonium laciniatum. , Coupled. pet uma wee
back to the year 1855,
when it suddenly arose from ordinary seed in a garden
at Lyons. Carriére reported that from this one plant
all double races and varieties of petunias have been
derived by natural and partly by artificial crosses, and
he added that likewise other species were known at that
time to produce new double varieties rapidly.
Geoffroy St. Hilaire, about 1825, expressed his belief
in saltatory variations as a means of evolution. He
thought that evolution does not take place entirely by
Mie
ale
NY
Mutations 59
the slow changes advocated by Lamark. His ideas were
theoretical, however, and at that time were not borne out
by experimental evidence.
Darwin recognized the appearance of sudden variations
of a marked character, such as is seen in the origin of
large-crested Polish fowls and short-legged Ancon sheep.
He thought that these new and strange forms would be
lost soon by intercrossing and, being rare, that they pos-
sessed no value. He held that the slow accumulation
of minute fluctuating variations was the important factor
in evolution.
De Vries’ experiment with enotheras. — De Vries became
convinced long ago that Darwin’s theory of the origin
of species through ac- |
cumulation of minute
changes was not the only
means of creating new
types. He determined
to produce mutations ex-
perimentally, if possible.
His results in the forma-
tion of a new variety of
the corn marigold will be
described later. After
making preliminary ex-
periments with some Fic. 16. — Hugo de Vries.
hundred species, de Vries
finally decided upon nothera Lamarkiana as the most
suitable form to use (Figs. 17 and 18). “Only one of my
tests met with expectations. This species proved to be
in a state of mutation, producing new elementary forms
60 Plant-Breeding
continually, and it soon became the chief member of my
experimental garden. It was one of the evening prim-
roses.” This G. Lamarkiana was found to produce a
large number of mutants, both when growing wild and
under cultivation.
The Gt. Lamarkiana plants which became the basis of
Fig. 17. — @nothera Lamarkiana and @nothera nanella in bloom.
future experiments were found growing wild in a field at
Hilversum, near Amsterdam, Holland. Little is known
of its history except that it is a native of America. It has
not been found growing wild in America in recent years,
although there seems to be evidence that it was seen and
collected in the Southern States in the last century. The
near relatives of @/. muricata, which were very common in
the sandy regions of Holland, are very stable; de Vries
Mutations 61
found no appreciable change in them, although he watched
them for more than forty years.
Lamark’s evening-primrose is grown in Europe as a cul-
_ tivated plant, used principally for ornamental planting.
It seeds abundantly and some of the plants have escaped
cultivation. Groups of plants are found growing wild
in many places. These wild plants remain in groups
rather than being widely scattered, suggesting a definite
hes
SW 1) i © 2 & a2 29 & 2S 26 27 28 29 30 3) 3239 déMm.
Fie. 18.— Enothera Lamarkiana. Curve exhibiting variations in the
length of fruits of 568 plants. The dotted line is that given by
Quetelet-Galton Law.
origin for each group. CM. Lamarkiana is described as a
“stately plant with a stout stem, attaining often a height
of 1.6 meters and more. When not crowded, the main
stem is surrounded by a large circle of smaller branches,
growing upwards from its base so as often to form a dense
bush. These branches in their turn have numerous
lateral branches. Most of them are crowded with flowers
in summer, which regularly succeed each other, leaving
behind them long spikes of young fruits. The pace are
62 Plant-Breeding
large and of a bright yellow color, attracting immediate
attention, even at a distance. They open towards
evening, as the name indicates, and are pollinated by
bumble-bees and moths. On bright days their duration
is confined to one evening, but during cloudy weather they
may still be found open on the following morning. Con-
trary to their congeners, they are dependent on visiting
Insects for pollination.
“In . Lamarkiana no self-fertilization takes place.
The stigmas are above the anthers in the bud, and as the
style increases in length at the time of the opening of
the corolla, they are elevated above the anthers and do
not receive the pollen. Ordinarily the flowers remained
sterile if not visited by insects or pollinated by myself,
although rare instances of self-fertilization were seen.”
(. Lamarkiana is a biennial, producing rosettes in
the first year and stems in the second year. This species
was found to be variable in all periods of its life cycle, —
in the seedlings, the rosettes, and the stems.
De Vries pursued three methods in obtaining his muta-
tions :—
1. Observations and studies of the plants while growing
in the wild state in the fields.
2. Some of the plants were removed from the wild state
and placed under cultivation. Many of the plants were
self-fertilized and their seed sown under controlled con-
ditions. By this method several mutants were found
which were too weak to withstand the competition of field
conditions.
3. Repetition of the sowing process for several genera-
tions, leading to the production of new forms.
Mutations 63
De Vries divided the new types of plants into five groups,
classified as follows :—
1. Retrograde varieties with ‘negative attributes,
—G. levifolia, A. brevistylis, and GE. nanella (Figs. 17
and 19).
Fig. 19. — Cnothera lata (left), CGnothera Lamarkiana (middle),
nothera nanella (right).
2. Progressive elementary species possessing new
characters, and appearing as vigorous as the parent plant,
CH. gigas and CZ. rubrinervis.
64 Plant-Breeding
3. Progressive elementary species, which are weaker
than the parent species, Gi. albida and C!. oblonga.
4. Organically incomplete forms, @. lata (Fig. 19).
5. Fertile but inconstant species forms, GZ. scintillans
and (. elliptica.
The new species and varieties may be described as
follows :—
Group I, retrograde varieties, which have lost some
of the characters possessed by the parent, 2’. Lamarkiana : —
(LZ. levifolia is easily distinguished from its parent,
CE. Lamarkiana, by having smooth, bright leaves, without
undulations. These leaves are narrower and more slender
than in Lamarkiana and the flowers of the brighter yellow.
This variety was constant from seed, showing no reversion.
It is a strong-growing plant and perfectly fertile.
(H. brevistylis is a short-styled form. The ovary of
this plant is abnormally situated and is not conducive to
proper fertilization. The ovary is reached by only a few
pollen tubes and fertilization must be incomplete. The
few seeds that are obtained reproduce this type without
reversion to Lamarkiana. (:. brevistylis may be dis-
tinguished from the other forms before blossoming as
the buds are much shorter and thicker than in the other
species. The presence of leaves more rounded at the
tip also distinguishes this form from others before
flowering.
(EL. nanella is a dwarf form, attaining often only one-
fourth the height of the other types. ‘The flowers on this
dwarf form are as large as upon Lamarkiana, which is a
striking feature. The size of the leaves is proportionate
to the height of the plant, but retain the same form as the
Mutations 65
parent species. The stems are unbranched and very
brittle. C. nanella is frequently produced as a mutation
and is absolutely constant (Figs. 17 and 19).
Group II, progressive elementary species, possessing new
characters : —
@. gigas is a giant form which is much larger in every
respect than its parent, except in height. The stems are
much larger; internodes are shorter and the leaves more
numerous than the parent species (CZ. Lamarkiana).
The flower-buds are large and closely crowded on the
spike, and when the flowers open, they make a beautiful
appearance (Fig. 20) .
(. rubrinervis is characterized by the red veins and red
streaks on the fruits. This plant is as tall as &. gigas,
but a little more slender. A feature of this type is the
brittleness of the leaves and stems, especially in the annual
individuals, of which many are found.
Many of these mutants may be recognized before the
adult stage has been reached, for example, at about the
age of two months. The leaves of @. gigas are broad, of a
deep green, the blade sharply cut off from the stalk, all
of the rosettes becoming stout and crowded with leaves.
In @. rubrinervis, on the contrary, the leaves are thin,
of a paler green, and with a silvery white surface ; the
blades are in the form of an ellipse, acute at the apex,
and gradually narrowing into the petiole.
Both of these species are quite constant and do not
revert to @. Lamarkiana. However, other mutants have
sprung from these two species, especially from rubrinervis,
which is produced in greater numbers from Berea
than is gigas.
F
Fic. 20.— A, spike with almost ripe fruits of @nothera gigas, a mutant
species; B, the same of @nothera Lamarkiana, its parent form.
66
Mutations 67
Group III, progressive elementary species which make a
very weak growth : —
(. albida has whitish, narrow leaves, apparently in-
capable of producing sufficient quantities of organic food,
and hence are very weak. These plants are not suffi-
ciently robust to withstand competition in the field and
require transplanting into rich soil in pots in order to
allow them to live through the first year so that they
can produce seed the second year. When these seeds
are planted they produce individuals true to type.
(. oblongaisasmall plant about half the size of Lamark-
zana and may be grown either as an annual or as a bien-
nial. It is characterized by its narrow leaves, which are
fleshy and of a bright green color. Another striking
feature of this type is the presence of numerous little
capsules covering the axis of the spike after the fading
away of the petals. CM. oblonga is very constant if grown
from pure seed.
The forms already described are relatively very con-
stant and never revert to the parent form. Contrasted
with these constant forms, de Vries found several incon-
stant types as follows : —
Group IV, organically incomplete types :—
(E’. lata is characterized by the fact that only pistillate
flowers are formed. The anthers seem to be robust,
but they are dry, wrinkled, and nearly devoid of contents.
It is a low plant with very dense and luxuriant, but brittle,
foliage. It has bright yellow flowers which open only
partially and remain wrinkled throughout the flowering
time. (. lata may be recognized by its seedlings, which
have leaves of a nearly orbicular shape and are very
68 « Plant-Breeding
sharply set off against the stalk. The mature plant
has broad sinuate leaves with rounded tips, which are
often crowded together on the summits of the stems and
branches to form rosettes. CM. lata may be considered
a true mutation, and when crossed with GZ’. Lamarkiana,
the progeny of the second generation segregates into
mendelian proportions, lata being recessive (Fig. 19).
Group V, perfectly fertile but inconstant species :—
(EZ. scintillans is characterized by the production of
deep green leaves with smooth, shiny surfaces, “glisten-
ing in the sunshine.” The plants are smaller and less
branched than the parental type. C. scintillans is a
very inconstant form; from the seeds which are produced
in great numbers, there results not only scintillans, but
Lamarkiana, oblonga, lata, and nanella, with a predomi-
nance of the parental Lamarkiana. In regard to its in-
stability, de Vries says, ‘‘The instability seems to be a
constant quality, although the words themselves are at
first sight contradictory. I mean to convey the con-
ception that the degree of instability remains unchanged
during the successive generations.”
(EL. elliptica is a very rare form both in the wild state
and in cultivation. It is characterized by having narrow
elliptical leaves and elliptical petals.
ANALYTICAL TABLE OF SEEDLINGS (After de Vries)
I. Leaves stalked.
A. Leaves of the same breadth or
broader.) —
1. Of the same breadth and shape,
not to be distinguished as
seedlings.
1 “(than in Lamarkiana)’’ as also in the other analytical tables.
a.
b.
Cc
Mutations
2. Broader, pointed, with many
erumples.
3. Broader, rounded at the tip
with very deep crumples,
a.
b.
edge incurved.
. Leaves narrower.
1. Broadest in the middle.
a. Very long with long stalks,
with narrow veins, almost
smooth.
b. Small with broad leaf-stalk
and broad, principal veins,
very smooth, shiny dark
ereen.
2. Of equal breadth over the
greater part of their length.
a.
b.
Green.
az le Only
slightly
rower, smooth with-
nar-
out, or almost with-
out ecrumples.
a. 2. Very narrow
broad
with
leaf-stalks
and broad _ veins
which often are red-
dish; wrinkled.
Whitish.
b. 1. Crumples
many,
pointed, narrowing
off into the stalk.
b. 2. Crumples few,
nar-
rowing off into the
stalk, wavy, brittle,
veins reddish.
DN
LE
TZ.
Pes outs is
69
. Lamarkiana.
. brevistylis.
. leptocarpa.
gigas.
Gta.
. semilata.
. elliptica.
. scintillans.
. levifolia.
. oblonga.
. albida.
. rubrinervis.
i
i EAL
es
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366 Plant-Breeding
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(This bulletin contains outlines for class studies and exer-
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and testing of seed corn, and the cultivation and breeding of
corn, with list of publications on the subject.)
1910. Crossy, Dick J., School Exercises in Plant Production.
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exercises in plant production, and contains outlines of
Appendix D 367
lessons in the structure and growth of plants, methods of
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368 Plant-Breeding
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Appendix D 369
the destruction of weevils or grain moths, the testing,
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to his locality.)
1910. Henry, A., On Elm Seedlings Showing Mendelian Results.
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380 Plant-Breeding
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Appendix D O87
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SON wee oe = 6 cok
G95. see ds = 764.5
(oo eee, kk = 874.5
BOLO: ES aE 50
500 18970.0
18970.0 = 37.94 cm.
500
We would get exactly the same result if we arranged the bean
plants, in order of size, in a single line, placing them end to end,
and then divided the total length of this line by 500, the number
of individuals in it. :
Average deviation. — One way of expressing variability is to
find out by how much, on the average, any individual in the
population deviates from the mean, the constant thus secured
being termed the average deviation. This is ascertained as
follows: the amount by which each class differs from the mean,
or in other words, the deviation from the mean (designated by
D) is multiplied by the frequency of the corresponding class,
and then-the sum of these products is divided by the total
1The Greek letter capital ‘“‘sigma’’ (2) indicates that the sum of
a series of values is to be taken.
The total number of individuals measured is designated by n.
Appendix E 405
number of individuals. The formula for the operation is Df.
n
Thus in our problem it would be found as shown in the table sao
V f D Df
Te aay: 28.44 113.76
WS. be 18.44 1327.68
29.5 x 169 8.44 1426.36
39.5 425 1.56 195.00
Ags oe Gt 11.56 739.84
BOR oe. an 21.56 819.28
Boel ae 31.56 347.16
BO ered 41.56 457.16
S95 % 2 6 51.56 309.36
5735.60
5735.60 _ 44.4712 em.
500
Of course, the deviations below the mean (28.44, 18.44, 8.44)
are negative quantities, those above (1.56, 11.56, 21.56, 31.56,
41.56, 51.56) positive, but inasmuch as we are here concerned
only with deviation from type, we are correct in neglecting these
signs, and using the arithmetic sum, and not the algebraic.
We would secure the same result if we went along our line
of bean plants spoken of above with an average or mean indi-
vidual as a measure, added up the lengths by which each one
missed of being an average individual, and then divided this
total by 500, the number of individuals measured. Clearly this
would give the amount by which, on the average, each individual
missed of being the mean or the average individual.
Standard deviation. — Another constant expressing departure
from type, and one which is preferred by biometricians on mathe-
matical grounds, is standard deviation, designated by the Greek
letter small ‘‘sigma”’ (a). It is found by squaring the deviations
from the mean before multiplying by the frequencies, dividing
the summation of these products by the number of individuals,
406 Plant-Breeding
and then extracting the square root of the quotient. The
formula is : — oe
Dey
C= =
le
V f Vf D Df D? Df
5-14 | 38.0 28.44 113.76 808.8336 3235.3344
15-24 72 1404.0 18.44 1327.68 340.0336 24482.4192
25-34 169 4985.5 8.44 1426.36 71.2336 12038.4784
35-44 125 4937.5. 1.56 195.00 2.4336 304.2000
45-54 64 £3168.0 11.56 739.84 133.6336 8552.5504
50-64 «=938 =. 2261.0 °21.56 819.28 464.8336 17663.6768
65-74 11 764.5 31.56 347.16 996.0336 10956.3696
15-84 =11 874.5 41.56 457.16 1727.2336 18999.5696
85-94 6 537.0 51.56 309.36 2658.4336 —_15950.6016
500 =18970.0 5735.60 112183.2000
M = 37.94 cm.
Av. Dev. = 11.4712 cm.
ao = 14.9789 cm.
Performing the operations indicated by this formula, we find
the standard deviation in our problem to be
112183.2000
= 14.
500 9789 em
The squaring of the deviations has the effect of exaggerating
the departures of the extremes, and thus the standard deviation
is always greater than the average deviation, so that the two
are not comparable. For the practical breeder the one is just
as good as the other and whether he employs the average devia-
tion or the standard deviation is of little practical importance
so long as he is consistent in the use of one to the total exclu-
sion of the other in the same piece of work.
Finding the mean and the standard deviation by the ‘ short
method.”’ — Where large numbers are used, the derivation of the
mean and the standard deviation by the method presented
Appendix E 407
above is a long and laborious process, in which the liability to
error is great. A much shorter, simpler, and at the same time
more accurate method has been devised. This consists in mak-
ing a guess at the mean (designated by G@), and indicating the
difference between each class value and this guess in a column
marked (V—G). Each of these differences is then multiplied by
the corresponding frequency and the algebraic sum of the total
negative differences and the total positive differences is found.
This is the total amount by which our guess missed the mean
for the whole population, and hence we should divide this
quantity by n to find the average amount by which we missed
our guess. If this amount, which is called the ‘‘correction,”’ is
positive, then our guess has been too low by that amount, and it
is to be added to the guess. On the other hand, if it is negative,
then our guess has been too high, and it is to be diminished by
this amount. The formula for this procedure is : —
correetion (c) = (Algebraic) 2J6V—@)
n
M=GeHte.
LENGTH oF PLants (SHORT METHOD)
V Ih (V—G) f(V—-G) f(V-—G)?
5-14 4 cay Ane Gear's 3600
15-24 72 Boge ato 28800
25-34 169 10... +1690 —3250 16900
35-44 125 0 0 0
45-54 64 10 640 6400
55-64 38 20 760 15200
65-74 1 30 330) 9900
75-84 af 40 440 17600
85-94 a 50) 300 2470-15000
500 Sum = _780 113400
Pig sell Ura C2 = 2.4336
408 Plant-Breeding
M = 39.5 — 1.56 = 37.94 cm.
c= 4 113400 _ 9 4336 = V224.3604 = 14.9789 cm.
500
14.9785
~ 14.9785 _ 39 4g og.
37,94 7
In our problem, the mean as determined by this method, as
shown in the accompanying table, is exactly the same as was
found by the long method, 37.94 cm.
We would have secured the same result if, after a casual in-
spection of the line of bean plants spoken of above, we guessed
that the mean was 39.5, and taking an individual of this length
as a measure, we found the total amount which the short ones
lack of being equal in length to the assumed mean, or the guess,
and likewise the total amount which the long ones exceed the
guess. The algebraic sum of these two amounts would be the
total amount by which our guess missed of being the true mean,
and since 500 individuals were measured, the average amount
by which we missed on each individual would be found by
dividing this sum by 500. Our assumed length would then
be corrected by this amount, just as above. If we had guessed
that the mean was 37.94, and went through the same process,
then the sum of the negative differences would have exactly
counterbalanced the sum of the positive differences, since our
guess in this case coincides with the true mean.
It would have made no difference whatever had we made our
guess at 9.5. Indeed, this would have the advantage that
minus signs would be eliminated and thus a frequent source of
error removed, since students are prone to forget the algebraic
signs. On the other hand, larger numbers would be involved.
In finding the standard deviation by the short method, the
elements of the (V—G) column are squared before multiplying
by the corresponding class frequencies. The sum of these prod-
Appendix E 409
ducts is then divided by n, just as in the long method. In find-
ing the mean a certain correction was applied to the guess.
Now, since we are here dealing with squares, we must apply as
a correction the square of the correction found previously ; but
unlike the previous procedure, this square of the correction is
always subtracted from the quotient found as stated above.
(All this has been proven mathematically correct, but the proof
is beyond the scope of this study.) The square root is then found
as before. The formula for deriving the standard deviation by
this method is: —
es haeegns
n
Using this method, we find the standard deviation to be
exactly the same as before, as shown in the table above and the
following calculations : —
5 =) 118400 (— 1.56)? = 14.9789 em.
A further considerable shortening of the short method can be
employed when the class values differ by amounts other than
unity or a simple multiple of it, such as 10. In such a case
the class differences are to be treated as unity and a correction
made at the end of the calculation. The modified formule are:
M=G + (c X True Difference between Classes).
o = | (e- e | x True Difference.
The short method, because of its simplicity and its labor-
saving features, recommends itself for general use. It is also
slightly more accurate than the long method because no deci-
‘mals are dropped until the very end of the calculation.
Coefficient of variability. — Standard deviation, as a measure
410 Plant-Breeding
of variability, allows of comparison only between similar organ-
isms or parts, between such characters as are measured in the
same denomination, as tubers with tubers, or height measured
in inches with height in inches. This is because it is not an
absolute, or abstract constant, but really represents a certain
number of feet, pounds, centimeters, or what not. And just as
we cannot compare 5 pounds with 5 inches mathematically, so
we cannot compare standard deviation in inches with that in
pounds.
An undenominational abstract constant that will allow of com-
paring diverse variabilities, let us say, height with thickness, or
pounds with inches, is designated as the coefficient of variability.
It is found by dividing the standard deviation by the mean.
The formula is ae < 100 and itissymbolized by C. Itis really
only the standard deviation measured in terms of the mean. For
our beans the coefficient of variability for length is .3948 or since
it is usually read as percentage, 39.48 %. This constant is now
comparable with any other coefficient of variability for what-
ever character or in whatever denomination it may have been
measured. Thus we can compare the variability in the length
of beans in millimeters with their variability in breadth meas-
ured in millimeters or inches, or with height in men or sugar
content in beets, if we wish.
Probable error. — Probable error does not mean the amount
of error that an investigator is likely to make in his experiments
or measurements. It means that if he would measure another
random sample of a population similar in size and character to
the sample he had measured before, the chances are even that
the mean for the new sample would lie somewhere between the
limits denoted by the probable error. Thus, the mean as to
length of plants for our beans is 37.94 em. with a probable error
of + .4518. This means that the mean for the new population
would not be greater than 37.9400 + .4518 = 38.3918 cm., or
Appendix EH All
less than 37.94 — .4518 = 37.4882 cm., but would fall some-
where in between these two limiting values. It is symbolized
by E with the initial of the constant to which it belongs attached
in smaller case type. Thus, the symbol for the probable error
of the standard deviation is E,; of the mean, Hy; of the co-
efficient of variability, E¢.
The probable errors are based upon certain relations between
the standard deviation and the number of individuals. The
greater the number of individuals, the smaller will be the prob-
able error. In short, the probable error will indicate how much
confidence we can place in our constant, and should always
accompany the latter. It is really a part of the constant.
In finding the probable errors the constant .6745 is used.
This has been derived mathematically and is used by all biom-
etricians in the same way.
The following formule will show how the various probable
errors can be found : —
E (G745 =:
SBE vi
Bs = -- .6745 Sere
V2n
oa 10% or less.!
v2
ae eae A
+ .6745 an 1+ 123 where C is greater than 10 %.!
Our completed constants for length of bean plants are then
as follows: —
M = 37.9400 + .4518 cm.
o = 14.9789 + .3195 cm.
C=3948 + .96%.
1In these equations the value of Cin per cent is to be used. The prob-
able error will come out as a percentage.
412 Plant-Breeding
In the accompanying table the constants for the number of
pods borne on these plants are likewise determined by the short
method. Note that the column (V—G)? is entirely omitted, a
short cut which is another considerable time saver. Instead, —
the elements of column f(V—G) are simply multiplied by the cor-
responding elements of the (V—G) column since f(V—G) times
(V-G) equals f(V—G)?.
NuMBER oF Pops (SHorRT MertuHop) \
vi J (V—-G) f(V-G) Ce Gye
5-14 16 —2(0) — 320 6400
15-24 140 —10 ae US Tae ie) 14000
25-34 169 0 O
35-44 115 10 1150 11500
45-54 40 20 ret) 16000
55-64 12 30 360 10800
65-74 3) 40 200 SO00
75-84 3 50 150 + 2660 7500
500 Sum = 940 74200
940
c =— = 1.88 eC = 3.5344
500
Mode = 29.5 ~ Modal Coefficient = 38.36 %
M = 29.5 + 1.88 = 31.38 + .3631 (pods).
: By Oe 3.5344 = 12.0360 + .2568 (pods).
500
_ 12.0360
~ 3836 = 38.36 + .93 %.
31.38 ted
EXERCISE 3
Correlation
Certain characters in organisms tend to appear together
and the inference is that they are causally connected, that is,
Appendix H 413
one is the cause of the other or else both are dependent upon
the same cause.
Two phenomena are causally connected if any one of the
~ following four cases is true: —
(1) If, when the first is present, the second is invariably present
also.
(2) If, when the first increases in amount, the second also in-
variably increases a proportional amount.
(3) If, when the first is absent, the second is invariably absent
also.
(4) If, when the first decreases in amount, the second also
invariably decreases a proportional amount.
Because a fixed or absolute relationship exists in each of the
four cases the correlation between the two phenomena is said
to be perfect, but in the first two cases it is positive in nature,
in the second two negative in nature. If absolutely no relation
existed between the two phenomena, the correlation would be
zero.
Now, in the bean problem used in the preceding exercise, it
might be asked, ‘‘Is there any fixed relation between the length
of plant and its number of pods?”’ Suppose, for example, that
if on selecting a plant from the whole lot, it was found to be a
long one, could we then say, on this information only, that it will
be found to bear a great number of pods? If so, we are assum-
ing that some relation exists between the two characters.
Let us, for the sake of illustration, suppose that each bean
plant bears one pod for every centimeter in length. Because in
this case there exists a fixed or absolute relationship, the corre-
lation is said to be perfect, and is expressed by 100 %, or more
usually simply by unity (1).
Now, suppose, however, that on selecting 300 plants averag-
ing 80 cm. in length, we find the first 100 plants to bear an
average of 50 pods per plant, the second 25 pods, and the third
10, it is clear that if we select one more plant at random and
414 Plant-Breeding
measure it to be 80 cm. also, we could no more predict the
number of pods it bears than if we had not.measured it at all.
Here, then, we say there is no relationship whatever between
length of plant and number of pods, or, in other words, the cor-
relation is 0.
Now suppose a third case, in which we find that invariably
the longest plant bears the fewest pods, and the shortest the
most. Here we could say the relationship is fixed or absolute
too, but in an opposite, or negative manner, and accordingly,
the correlation would be expressed by — 1.
But now turning back to the first supposition, where it was
assumed that one pod was borne for each centimeter length,
suppose that the relationship were not so definite. Suppose
that one pod occurs not for every centimeter, but sometimes for
a little more than a centimeter, sometimes for a little less; then
the relationship, though not absolute, is high, and the degree
to which this relationship approaches the perfect 100 % relation-
ship will express the correlation between the two characters.
The correlation coefficient, in other words, would fall between
0 and + 1.
We rarely find characters or organs in an organism to be
absolutely related; usually they are associated in a more or
less intermediate degree, somewhere between 0 and + 1, or
0 and — 1. The degree to which they are associated, or corre-
lated, if it can be determined in an exact manner and expressed
by a mathematical constant, should be an index of the degree
for which one is the cause of the other, or the probability of
finding the other when we know the first is present. This may
be of importance sometimes to the breeder because some easily
seen character may be responsible for, or indicative of, the
presence of a desired, but unseen character. Thus a certain
shaped kernel of corn (one with a large germ) is known to run
high in oil content, one with large endosperm high in starch.
To select kernels with large germs is much easier than to analyze
Appendix E 415
many ears by chemical methods. Or if, after a relation had
been established, we could safely choose the longest or tallest
bean plants right in the field and know that they will bear the
greatest number of pods, it would be of great advantage to the
breeder.
Now, an exact determination of the degree of correlation can
be obtained by the biometrical method. Let us follow the pro-
cess step by step, using our bean data.
First of all, we take our data for the two characters for which
we wish to find the correlation, length of plant, and number of
pods.
Our original observations will be somewhat as follows : —
No. oF OBSERVATION
(or PLant) LENGTH OF PLANT IN Co. No. or Pops
1 27 32
2 46 Q7
3 18 | 45
etc. etc. etc.
In finding the constants — mean, standard deviation, etc., for
each of these characters, the observations for length and those
for number of pods were distributed in separate tables. Now,
however, we distribute both sets of observations on one table,
in what are known as arrays of a correlation table. (See Table
1.) For example, the first observation tabulated above would
fall in the vertical array 25-34, as regards length, and in the
25-34 horizontal array, as regards number of pods. The second
observation would fall in the 5th column (vertical array 45-54)
and in the third row (horizontal array 25-34).
Thus each vertical array would be a frequency distribution
of length of plant with respect to number of pods, and each
416 Plant-Breeding
horizontal array would be a distribution of number of pods
with respect to length of plant. But if we add up all the fre-
quencies along each horizontal array, we will get the frequency
distribution with respect to the number of pods and it will be
exactly the same as that found in the preceding exercise (see
table on p. 404); likewise, if we add up the frequencies in the
vertical arrays, we will get the frequency distribution with
respect to length of plants.
The various steps by means of which the constants for length
of plant and those for number of pods were obtained were
given in the preceding exercise and need no repetition. They
are here secured by the “short method” and are given in the
correlation table. We are here concerned with the finding of
the constant which will express the degree of correlation between
these two characters.
The only new feature of this correlation table, aside from the
method in which the observations are distributed, is the column
marked 3P. Kach element of this column represents the total
deviation (from the assumed mean, or guess) of the individuals
in each array with respect to both length of plant and number of
pods. Thus, taking the first horizontal array, the 5-14 class
as regards number of pods, we wish to find how much the in-
dividuals in this class deviate from the assumed mean for length
of plants. It is found as follows : —
3 individuals each deviated by — 30 = — 90
9 individuals each deviated by — 20 = — 180
3 individuals each deviated by — 10 = — 30 — 300
1 individual deviated by + 20 = 20 + 20
Algebraic Sum = — 280
All the individuals in this array deviate from the assumed
mean for length of plants by the algebraic sum of the total minus
deviations and the total plus deviations, which is — 280, as
indicated. But each individual in this array with respect to
Appendix E 417
length deviated by — 20 from the assumed mean with respect
to number of pods, and hence we must multiply — 280 by — 20
to find the total deviation from both assumed means and this
gives us + 5600.
All the elements in the =P column are secured in exactly the
same way. The third element is zero, since the deviation from
the assumed mean for number of pods is zero in this case. The
fourth element comes out a minus quantity according to the
following calculation: —
1 x —30 = — 30 18 x10 = 180
11 x — 20 = — 220 5 x 20 = 100
42 x —10 = — 420 2x30 = 60
oo xX = ) Ls 405 =~ 40
— 670 a eo = 108
480
— 670 + 480 = — 190 x 10 = — 1900.
The algebraic signs for each quantity must be carefully ob-
served throughout the calculations.
Finally, the algebraic sum of all the elements in the SP column
is determined.! This will give us the grand total deviation from
both assumed means for all the individuals, and hence to find
the deviation for each individual we must divide by 500. Per-
33100
0) = 66.20.
Now all along we have been working from an assumed mean,
or guess, and we must apply a correction, which, mathematicians
tell us, must be the product of the correction for length by that
forming the operation we get
1 The elements of the 2P column can be obtained by finding the total
deviation of each vertical array with respect to number of pods and
multiplying by the deviation of that array with respect to length, instead
of vice versa. The elements will be different, but their sum will be
exactly the same by either method.
25
Plant-Breeding
418
aye)
G6E
spog jo aquinn
See ea ee eee See eo eee
Ena RSET ENE eae eee Rees oY Te Weeaee
(O9E0'S1) (68L6°F1) _ 5 MSE ese = = = = = = = :
oe ane 00g 1} + |
(9¢'T (S8'T)] = Oolee = x is a
% 86’ F 9E'8E %96 °F 8h'6E= 0 |S] SO = =
spod g9¢z° F 09€0'ZI ‘WH G6IE’ F LZ8L6FI = 2 | | a
spod [¢9§° F SEIE ‘“WISICh + FelZE= W - a as,
Prec es 98'S = wO w _ rot) “I for) D> "—
88'T OPES Oe alle Oe SoU re ot so Sele Meare
Spog ‘ON qysu0T | | | =
on HS ou) no an ee bo Je) A
; =) (=n) S (=) (=) (=) j=) (>) (jo)
Ou
(=) ron feos —
=) = - oo D> wo > =
OOTEE O0CEL OF6 OOM fs = G0 a on © S ee
0008 oosz | 009% ogt o¢ |e | e 7S-¢2
OO8F 0008 00% OF G j SG I £1-S9
0099 OO8OT 09g og ZI I ‘6 I ¢ I & if £9-S¢
000¢ O0009T 008 OZ OF I ¢ I 9 ¢ els Ol I $S-CF
O06I— | OOSTT OSII OL Gy ra I jG c SI CG: Bip Croat elect lee ies
0 0 0 691 F Z FI GGa) eGr 16S ean PE-GS
OOO0T OOOFT | OGZI— OOFI— | OI— | OFT I 9 ZI Of NeP7Gn Ze C-SI
009¢ 00F9 Oz — | OZ— | OL I g 6 © IFS
dz x(D-A) § ()-A) 3 D-A J} || F6-G8 | F8-GZ | $2-C9 | F9-Gs | $9-CF | FF-SE | FE-CS | FZ-ST|FI-G| A
"md ¢'6Z = D ‘Ud UI JURT JO 4VsUIT
sadog 40 uaaWON X INVIG JO HLONGT NOILVIEUOD
I WIidVvL
Appendix E 419
for number of pods. This product is always subtracted from the
quotient of a
66.20 — (1.88 x — 1.56) = 69.1328.
Now this corrected deviation must be secured in terms of the
standard deviations for each character, and hence this quantity
69.1328 is to be divided by the product of both standard devia-
tions :—
9
69.1328 — 3835.
14.9789 x 12.0360 —
We have now finally arrived at our correlation coefficient,
designated universally by the letter 7, the formula for the deter-
mination of which is as follows : —
>P
SS er ee
Correlation Coefficient (7) =
GO; G2
Like all other constants the correlation coefficient must be
accompanied by its probable error, the formula for the finding
of which is as follows : —
wy?
res .6745 iPS 7)
vn
Solving this for our correlation coefficient, we find the prob-
able error to be + .0257.
The amount of confidence which can be placed in the corre-
lation coefficient depends upon the size of its probable error
largely. Biometricians say that in order to be of much value,
the coefficient must be from five to ten times as great as its
probable error. But whether the coefficient shows a high, low,
or intermediate degree of correlation between the two charac-
ters measured depends entirely upon its position with reference
to its two limits, 0 and +1 or 0 and — 1. According to the
420 Plant-Breeding
size of r found for the data used in our problem, the correlation
existing between the length of plant and its number of pods is
not great.
EXERCISE 4
Statistical Study of Apples from Different Trees
Object. —'To study the individuality of fruit trees.
Materials. — Apples representing the total product of different
trees; scales; calipers.
Fill in the following form for each tree. Plot curves repre-
senting the entire population of trees.
| |
NAME OF VARIETY |
Tree no.
Age of tree
Condition of tree
Total number of apples
Number of marketable apples
Total weight of apples
Weight of marketable apples
Average width of 50 apples
Average length of 50 apples
COLOR) 259 ey TAME oes tr ee ie eve
Any other noticeable differences
EXERCISE 5
Statistical Study of Branches of Different Trees
Object. — To continue the study as outlined in Exercise 4,
to test the individuality of trees.
Materials. — Fruit trees of different kinds, preferably dwarf
trees; tapes.
Measure the new growth of various parts of each tree and of
different trees. Plot curves of each tree and of all of the trees
Appendix EK 421
Fig. 108. — A common form of ragweed,
422 Plant-Breeding
Fic. 109.— Another form of ragweed.
Appendix E 423
as a population, to show graphically the extent of bud variation
present.
EXERCISE 6
Statistical Study of the Quantity of Grapes from Different Grape
Vines
Use the same general method as in Exercise 4.
EXERCISE 7
Study of Variation in Pressed Specimens of Ragweed or Some
Plant showing Many Different Types
Object. — Careful study of the large and small variations among
different biotypes of ragweed (Ambrosia artemisiifolia).
Materials. — Specimens of many different types of the above
plant or any species of plant which is rich in biotypes. These
specimens should be carefully pressed and mounted. (See Figs.
108 and 109.) Have each student make detail drawings to show
minute differences.
EXERCISE 8
Study of Bud Variations and Reversions in Ferns
Object. — To determine the nature and amount of reversion
from the parental type, and if possible to find some cause for
the same.
Material. — Obtain specimens of the sword fern (Nephrolepis
exaltata) and Boston fern (Nephrolepis bostoniensis) and as many
of the other ferns named below as possible.
Study the trueness to type of each variety and any reversions
which they may contain. Draw typical specimens.
The following is the history, according to Cogswell, of some
of the fern varieties. This is not a complete list but gives
an idea of the origin of a few common horticultural varie-
ties.
424 Plant-Breeding
INTRO-
DUCED IN SPORT OF
(about) | nephrolepis
Nephrolepis bostoniensis. . . . . 1880 | exaltata
(sword fern)
Nephrolepis Pierson. 37.04... 5°. 1903 | bostoniensis
Nephrolepis elegantissima . .. . 1904 | Piersonii
Nephrolepis ‘Scotti; (1). we ee 1904 | bostoniensis
Nephrolepis; Barrowsil ~=2" 24) 2aey <. 1905 | Piersonii
Nephrolepis Whitmaniti .. . . . 1906 | Barrowsii
Nephrolepis todeaoides 4° 3 0. 1907 | Whitmanii
Nephrolepis superbissima . . . . 1908 | Scottii
Nephrolepis’*Scholzehi 2°02" .64 0 s.4 1909 | Scottii
Nephrolepis Pruessnér,- 2 9. « -:... 1909 | Whitmanii
Nephrolepis magnifica . . . : 1908 | Whitmanii
Nephrolepis elegantissima compac ta : 1909 | elegantissima
EXERCISE 9
Study of the Morphology of Different Kinds of Flowers
Object. — To acquaint the student with floral parts and their
functions. To determine the proper condition of the buds and
flowers for emasculation, crossing, etc.
Material. — Buds and flowers of various kinds and in different
stages of development; microscope or hand lens; set of dis-
secting instruments. The material should represent different
natural families or orders.
Have the students make careful drawings of the floral organs,
of various types of flowers. Take special care to distinguish
the stamens and pistils.
The following outline by Dr. M. J. Dorsey may be found
helpful in this exercise : —
Appendix E 425
Stupy or FLowers (prerequisite to crossing)
_ Flower —
Non-essential organs —
Calyx — composed of sepals.
Corolla —composed of petals.
Essential organs —
Pistil — | carpels.
a, style; b, stigma; c, ovary { placenta.
ovules.
Stamens — composed of
{ loculus or cell.
a, filament; 6, anther
pollen.
Degree of cross-relationship. —
1. Self- or close-fertilization. (Occurring in perfect or her-
maphrodite flowers.)
2. Cross-fertilization. (Between individuals of same species
or variety.)
3. Hybridization. (Between species and sometimes between
varieties which are very distinct.)
Causes of sterility. —
1. Stamens and pistils maturing at different times. (Di-
chogamy.)
' 2. Lack of affinity between pollen and stigma.
3. Scanty or insufficient pollen.
4. Lack of viability of pollen.
Relative position between stigma and anthers. —
1. Stigma and anthers the same height.
2. Stigma above anthers.
3. Stigma below anthers.
426 Plant-Breeding
Relative maturity of pistil and anthers. —
1. Both maturing at same time.
2. Stigma matures first — protogyny.
3. Anthers mature first — protandry.
Methods of pollination. —
1. Insects.
2. Wind.
3. Water.
4. Self-pollination.
Types of plants in regard to sex. —
1. Moncecious (both sexes on same plant).
2. Dicecious (each sex on different individuals within the
species or variety).
3. Polygamous (perfect and imperfect flowers on the same plant).
Types of flowers in regard to sex. —
1. Imperfect (1) Staminate — bearing only stamens.
(2) Pistillate — bearing only pistils.
2. Perfect or hermaphroditic — bearing both stamens and
pistils. Determine the following : —
(a) Number of parts of flower. —
a, sepals; b, petals; c, stamens; d, pistils.
(b) Type of flower — perfect (hermaphrodite) or imperfect.
(c) Relative position of stigma and anthers.
(d) Relative maturity of pollen and stigma.
(e) Is the flower pollinated by insects, wind, or selfed?
(f) Draw the essential organs and label each part.
EXERCISE 10
Technique of the Cross-pollination of Plants
This exercise may be carried out in the winter in a green-
house or conducted in the fall and spring out of doors, where
Appendix E 427
additional expense is not involved in growing the plants under
glass.
The following suggestive directions may be given to each
student : —
Materials. —1. Instruments: tweezers; scalpel; small, sharp-
pointed scissors, hand lens, etc.
2. For covering flowers: Manila bags, waxed paper bags,
cheese cloth, etc. Wire labels, stringed tags, fine copper wire
or twine cut into short lengths may be used to fasten the bags.
Preliminary study of plant. —
Before attempting to cross plants, it is necessary to know the
structure of the flower to be used. To do this (A) locate
all parts — sepals, petals, anthers, filaments, stigma, style,
ovary; (8) determine whether the flowers are perfect or
imperfect; (C) learn to recognize the “ripe” or receptive
condition of the stigma and pollen.
Technique. —
(A) Emasculation. (Unnecessary where stamens and pistils
are borne on different flowers.) For crossing purposes
select flowers in which the anthers have not opened. Re-
move the anthers with tweezers or scalpel, taking care not
to injure the stigma. It may be necessary to remove part
or all of the petals in some flowers in order to get at the
anthers, but it is best to remove only the anthers, if possible.
(B) Bagging. After the anthers have been removed, the
flower should then be covered with some material, as a
manila or oil paper bag, to prevent the entrance of foreign
pollen. When the stigma is receptive, remove the covering,
pollinate with the desired pollen of known purity, and im-
mediately cover again, leaving cover on until fertilization
has taken place — as indicated by withered or brownish
stigma. It is desirable to remove the covering when the
cross has “‘set.”’
428 Plant-Breeding
(C) The record. The record should include a description of
each parent, giving particular attention to the contrasted
characters. Colors may be recorded by comparing with a
standard color chart. The female parent should always be
mentioned first. The record on the label should include |
variety name or number of each parent, date of emascula-
tion, and pollination. (Name of worker can also be placed
on the label.) As far as possible reciprocal crosses should
be made.
EXERCISE 11
Embryological Studies from Slides showing Cell Division at Dif-
ferent Stages, Chromosomes, Pollen Mother-cells, Development
of the Embryo-sac, etc.
Provide each student with a high-power microscope and mi-
croscopic slides mentioned above. Careful drawings of each slide
should be made.
EXERCISE 12
Study of Pollen Germination and Fecundation
Materials. — Fresh and preserved flowers showing structure
of carpels in cross and long section; microscopic slides showing
growth and penetration of pollen tubes into ovary, fecundation,
etc. For study of germinating pollen, fresh pollen may be
germinated in sugar solutions of various strengths mounted in
the cells of hanging-drop slides. If this is done at the beginning
of the practicum, the germinated pollen will be ready for ex-
amination before the end of the period.
Careful drawings of all stages observed should be made. The
drawings should show all the differences in the length and size
of the pollen tube in various degrees of concentration of the sugar
solutions. Note also the effect of temperature and other external
influences upon germination.
Appendix EH 429
EXERCISE 13
Practice in the Cross-pollination of Apples, Pears, Peaches,
Plums, ete.
To be carried on in the spring, when the trees are in bloom.
For general methods of procedure, see Exercise 10.
EXERCISE 14
Purpose. —To teach the Laws of Probability ; dominance
and recessiveness; segregation and recombination; presence
and absence hypothesis; inhibitory factors; complementary
factors; inversed ratios, ete.
Materials. — Coins, wrinkled and smooth peas, bath yellow
and green in equal numbers for two character pairs; yellow and
white kernels of both dent and flint corn ; a pack of playing
cards; and chemicals.
Program. — The instructor should take special care to make
clear the significance of each step in the exercise and their con-
crete application to problems of plant-breeding and genetics.
1. The Law of Probability is taught by tossing coins. Each
student should toss one coin for 2 or 3 minutes and record the
number of times it falls head, and the number of times tail.
Then the total for the whole class is summed up. It will be
found that the latter count, including more tosses, approaches
the theoretical ratio much more nearly. This should be ex-
plained by the instructor.
2. Then in the same way two coins may be tossed by each
student. He now records heads; heads and tails; tails.
The application of this law in the formation of gametes should
be made clear by the instructor.
3. Now the material may be changed by way of illustration.
Peas or corn comprising two allelomorphs may be used for this
exercise. They are mixed together in equal numbers in a bag
430 Plant-Breeding
and each student draws blindly from the bag one seed at a time,
recording his draw. This exercise illustrates segregation and
the formation of gametic cells.
4. Now each student may remove simultaneously one pea
from each of two bags, and lay them down side by side to illus-
trate the mating of gametes in an F, hybrid and the subsequent
recombination of characters. He should record only the domi-
nant characters present in each pair taken and his record will
show the phenotypes of his F, hybrids.
5. The same principles can be illustrated by the use of a pack
of playing cards. Draw at random two cards at a time. Record
each combination observed. Two blacks coming simultaneously
represent a homozygous black individual; a black and a red
represent a heterozygous form appearing as black, two reds
represent a pure recessive. For illustrating the combination of
two character pairs, four cards may be drawn at a time.
6. Some simple chemical reactions ! afford an excellent series of
demonstrations illustrating the main features of Mendelism.
The following apparatus and chemicals are required : —
4 500 ce. flasks 3 dozen test tubes
1 100 ce. flask 4 small funnels for burettes
1 100 ec. graduate 1 iron stand and clamps
4 50 ee. burettes 3 test tube racks
1 2 ce. pipette 1 pipette dropper
500 ce. 10% ep. NH.OH 500 ce. 5% ep. HCl
500 ce. 25% ep. NH,OH 100 ce. 2% litmus powder
500 ec. 10% ep. HCl solution
10 ce. phenolphthalein
While the burettes are not absolutely necessary, they will
greatly facilitate the demonstrations. The solutions are to be
made up beforehand by the instructor, who should try some pre-
1 This portion of the exercise is based on an article by G. H. Shull,
‘“A4 Simple Chemical Device for illustrating Mendelian Inheritance,”
Plant World, 12: 145-153, 1909.
Appendix EH 431
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Y
GS] C+
QI
q
¥
Pee
q
q
Fig. 110.
432 Plant-Breeding
DEMONSTHATION GF FAESENLE ANT AGSENME HYPOTHES/S
ANT GF INTEFIMEDALY
A SHEE.
O27,
Lameles Fi ZyGOIrS
AA
SS
Wd
Hig Geral
Appendix KH 433
liminary experiments to see whether or not the strengths of ‘the
solutions are correct. They may have to be varied slightly.
The contents of each test tube representing a gamete (labeled in
the accompanying figures) are given below. In order to secure
the simple 3:1 or 1:3 ratio in F», eight test tubes representing
the gametes of F; are necessary in each case. It is of course
impossible. to represent the phenomenon of segregation in F
by using the test tube labeled F;. The instructor will have to
explain that after segregation the gametes are exactly the same
in nature as those of the original parents of the cross, and that
the hybrid F; now forms gametes similar to those of both parents,
in equal numbers.
(a) Demonstration of Allelomorphism and of Complete
Dominance (Fig. 110).
D contains 10 ee. 10% HCl + 2 ec. litmus solution.
R contains 10 ee. 10% NH4OH + 2 ce. litmus solution.
The dominance of blue over red can be shown by substituting
5% HCl for the 10 %.
(b) Demonstration of the Presence and Absence Hypothesis
and of Intermediacy (Fig. 111a).
A contains 10 ee. 10% NH,OH + 2 drops Phenolphthalein.
a contains 10 ec. 5% ACI.
(c) Demonstration of Complementary Factors (Fig. 111b).
A eontains 10 ce. 10% NH,O8H.
B eontains 10 ec. H,0 + 2 drops phenolphthalein.
Dominance of a character has usually been taken to be indica-
tive of the presence of a positive factor determining that char-
acter. But in some eases the absence of a factor, e.g. cases of
awnlessness in wheat, or hornlessness in cattle, seems to be
dominant over its presence. To say that the absence of a thing,
in other words a purely negative condition, is dominant over its
2F
434 Plant-Breeding
TIEMONITHATIIN, GF THE FPHESENLE GF AN IMNEITO? § FALTO
A a
DAME/ES
|
[ a8
t ,
BG 2?
Appendix E 435
presence seems an absurdity. However, to make the facts
consistent with the presence and absence hypothesis, two expla-
nations are offered. One consists in assuming the presence of a
positive inhibitory factor, which prevents the production of the
character concerned. The other consists in assuming that one
“dose ’’ of the factor concerned is insufficient to produce the
result, hence in its simplex or heterozygous condition, the char-
acter determined by the factor fails to appear, and it is only
when the factor is in the duplex or positively homozygous con-
dition that it does appear. The first of these explanations is
embodied under demonstration (d). The last is embodied
under the demonstration entitled ‘Explanation of So-called
‘Dominance of Absence.’ ”
(d) Demonstration of the Presence of an Inhibitory Factor
(Fig. 112).
A contains 10 ec. 2.54% NHsOH +2 drops phenolphthalein.
Ai equals A +5 ce. 10% HCl.
(e) Explanation of So-called ‘Dominance of Absence”
(Fig. 113).
A contains 10 ce. 10% NH,OH +6 drops phenolphthalein.
a contains 10 ee. 10% ACI.
After the zygotes of F, are obtained, in this last demonstration,
the instructor should add 10 cc. — 10% NH,OH to each Aa
zygote of F. to show that another “dose” of factor A will now
produce the result.
EXERCISE 15
A Study of Mendelian Characters in Timothy and Oats
Purpose. — To afford the student concrete illustrations of
Mendel’s laws; to find unit characters in plants and to see their
segregation and recombination.
Materials, — Mature timothy plants of various strains, com-
436 Plant-Breeding
EXPLANATION QF SO-LALLEQ TIOMNANEE GF AGSENEL”’
2 Aa
Cae | LAG
a
DATES Fo Z2yG0lrs
—
a ee
ime.
i:
iL
j— JI
Wives ably
Appendix E 437
prising as great a variety of unit characters as possible. A small
bundle of stems for each student containing samples from different
plants. Photographs and mounted specimens. Varieties of
oats comprising various unit characters that may be readily
distinguished in hybrid plants, such as black and white grains,
side and panicled types of inflorescence; also bearded and
beardless varieties of wheat or barley. Specimen plants of
parent types should be available for inspection, also specimens
of the F; plants. A large number of F; plants resulting from each
cross studied should be available for examination by the class.
Program. — 1. The instructor should first explain the purpose
of the afternoon’s exercise and outline the order of procedure.
Unit characters are to be studied and illustrated with timothy
and oats or barley. Dominance, recessiveness (or presence and
absence), segregation, and recombination can be illustrated here.
2. At this occasion a talk may well be given on artificial
crossing of small cereals for the purpose of creating new varieties.
The instructor may describe the inflorescence of the oat plant,
and the technique of making crosses in these plants. He should
illustrate the talk with charts and with diagrams made on the
blackboard.
3. Mounted specimens of oat types together with the F, and
F, progeny resulting from their crossing may be handed around
for examination by the class. If enough mounts are available,
the specimens may be drawn and described by each student.
4. Composite samples of timothy should be handed to each
student. He should study them to see what diversity of unit
characters can be found there, in the nature of differentiating
botanical characters. A list should be made of all the unit
characters observed. Drawings of timothy heads may help to
train his observation and fix the idea.
5. A large progeny of F, oat plants should be distributed
among the class after the parent types have been shown and their
differentiating characters discussed. The class may now examine
438 Plant-Breeding
the plants given to them, and sort out the segregated characters.
When sorting has been completed, the counts for the whole class
may be ascertained. It should serve to illustrate the expected
theoretical mendelian ratio.
Remarks.— Timothy affords very good material for this prac-
ticum, especially when bundled and mounted specimens, together
with photographs, are available.
Oats exhibit excellently contrasted unit characters, but expe-
rience shows them rather poorly adapted for class study, except
when mounted specimens are used. The reasons for this are : —
1. Side and panicled characters — the specimens are often
pressed out of shape, due to drying and storing, and are, therefore,
difficult to distinguish.
2. Color. — Black oats crossed with white give oats of inter-
mediate color which are often difficult to distinguish from black.
White and yellow are impossible of being distinguished by the
inexperienced student. Moreover, color in oat hulls varies
greatly with the seasonal conditions under which it was grown.
3. Plants are likely to become broken up in handling, thus
spoiling the count when mendelian ratios are expected. The
first two of these objections can be obviated by using mounted
specimens. Other characters such as naked, hulled, awned, and
awnless can be illustrated in this way. Probably a better exer-
cise would be given by substituting corn for oats.
EXERCISE 16
Mendelian Problems
Purpose. — To enable students to become familiar with what
might be called the mechanics of mendelism by working out
mendelian problems by the method of squares.
Problem. — Given: Two pairs of contrasted characters —
Tall vine (7), dwarf vine (t); Yellow seeds (Y), green seeds (y).
Tallness and yellowness are completely dominant characters.
Appendix E » 439
1. What gametes will be formed by an F, hybrid individual
from the cross between tall, green and dwarf, yellow ?
2. How many offspring will it be necessary to grow in order
to allow every combination to appear in the second generation ?
3. How many genotypes will there be?
How many phenotypes will appear?
In what ratio will the phenotypes appear?
How many pure dominant individuals?
How many pure recessive individuals?
If the combination T Xt gave plants of medium height
ion a tall plant with yellow seeds is crossed with a dwarf plant
with green seeds, how many genotypes will appear in F.? How
many phenotypes? In what ratio?
Illustrative problems. — The following problems may be studied
by way of illustration. These are taken from actual cases with
the tomato, but will apply in principle to other plants, by sub-
stituting other unit characters : —
Problem 1.—
Tall, homozygous (7) x dwarf, homozygous (t) = Tt; F,
F, gametes = T';t
Be eee ee
F, selfed =
POLLEN-GRAINS
fig 's
Te ft tT
EGG-cCELLS
t Ws tt
440 > Plant-Breeding
Phenotypes (visible types) (2%) = 3 TT; 1 tt.
Genotypes (actual types) (8%) =1T7T; 2 Tt; 1 tt.
Problem 2. —
Heterozygous Tall (Tt) x homozygous dwarf (tt).
Whenever a plant which is already heterozygous is used as a
parent, its gametes will become segregated during their formation,
and when the crossing takes place more than one kind of progeny
will be produced. In this case the female parent will produce
two kinds of egg cells, namely, tall and dwarf.
Graphically, this cross may be represented as follows : —
PoLLEN GRAINS
t t
Eae CELLs
The male parent is pure dwarf, therefore all of the pollen grains
will represent dwarfness only.
Phenotypes = 2 Tt; 2 tt.
Genotypes = 2 Tt; 2 tt.
If the female parent were crossed with a homozygous tall
instead of a dwarf, the visible types the first year after crossing
would all appear the same (tall) instead of two kinds as above.
There would be
Phenotypes = 4 TT.
Genotypes =2T7T; 2 Tt.
Appendix E 441
Problem 3. —
The cases which have been considered hitherto show perfect
dominance of one unit over another. This is not always the
ease. It frequently happens that the first generation hybrid
is intermediate between the two parents, and in the second gen-
eration the heterozygote forms differ from either homozygous
form. Thus when large, round tomatoes are crossed with small,
plum-shaped ones, the F; hybrid is intermediate between the
parents. If ZL represents largeness and (/) small, plum-shaped,
then F, hybrids (ZI) will not be the sameas (LL), but will be
distinctly different. The formule previously given, 2”, 3", etc.,
will not hold in cases of incomplete dominance. This will be
more fully explained later. Large (LZ) X small, plum-shaped
(lt) = Ll, an intermediate type of fruit.
F, gametes = L, l.
F, selfed =
PoLLEN GRAINS
L l
L LL a
Eaa CE.LLs
l Ei ll
Phenotypes = 1 LL; 2L1; 1 ll
Genotypes =1 LL; 211; 1 ll.
Problem 4. —
Intermediate (Zl) x Large, round (LL)
442 Plant-Breeding
PoLLEN GRAINS
L L
ip LL LL
Eee CELLS |
l Ll Li
Phenotypes = 2 LL; 2 Ll.
Genotypes =2 LL; 2 Lil.
Problem 5. —
Tall, smooth (Th) x dwarf, Hairy (tH) = Tall, Hairy (TtHh)
Pvcametes: = i Ph tid 5 tie.
F,selfed =
PoLLEN GRAINS
TOT: Th vee th
Shak
Th
Eca@ CELLS
Appendix E 443
Phenotypes (2") = 9 TH; 3 Th: 3 he Ra a fe
Genotypes (3") = 1TTHH,1TThh, 1 ttHH, 1 tthh, 2 TTHh,
2 ttHh, 2 Tthh, 2 TtHH, and 4 TtHh.
~ Problem 6. —
Tall (Heter)! smooth (Tth) x dwarf, Hairy (tH).
Female gametes = Th, th.
Male gametes = ?¢H.
PoLLEN GRAINS
tH
Th TtHh
Eaea CEs
th ttHh
It will be seen that two types are produced the first year after
crossing instead of the one where pure parents are used. Segre-
gation takes place immediately in the female parent because of
its hybridity, and two kinds of gametes will be produced.
In order to get a comparison with the F, when pure parents
are crossed, it is necessary to self both types as follows : —
(a) TtHh produces gametes as follows, Th, Th, tH, th. These
are the same as in problem 5 and hence the resulting plants will
be: —
Phenotypes = 9 TH, 3 Th, 3tH, 1 th.
Genotypes = 1 7TTHH, 1 FThh, 1 tHHA, 1 tthh, 2 TTHh,
2 tHh, 2 Tthh, 2 TtHH, and 4 TtHh.
(6) ttHh produces the following gametes: tH, th.
<2 1! ister’! is used ‘for short in place of heterozygote, similarly ‘“‘homo”
is used for homozygote.
444 Plant-Breeding
POLLEN GRAINS
tH th
tH
Eaa@ CELLS
th tt tt
Hh hh
Phenotypes = ttHH, tthh.
Genotypes = ttHH, 2 ttHh, 1 tthh.
Problem 7.—
Tall, large-round (7L) x dwarf, small plum-shaped (tl) = Tall
intermediate (TtLl).
Hy eametes = TD: Tle ue sil:
POLLEN GRAINS
TL ia tL tl
Ri CELE | Pr U Ti TtLl
Taner
Tl UIC INN A IEE: HT by5 Ttll
Eaa CELLS ; =
iL TOT | REEL (tLL ttLl
tl TtLl | Till (tL tll
It must be remembered in this problem that we have incom- |
plete dominance in one allelomorphic pair, therefore the number
of visible types is different than in cases where both units exhibit
dominance.
Appendix E 445
Phenotypes = 3 TTLL, 6 TTLI, 3 TTI, 1 t#LL, 2 ttLil, 1 till.
Genotypes = 1 7TLL, 1 TTU, 1 ULL, 1 tll, 2 TTL, 2 Tiil,
2 Till, 2 wLl, and 4 TtLi.
What visible types would be produced if incomplete dominance
occurred in both characters?
Problem 8. —
Self-fertilize-Tall, intermediate (77TZI1). This is a pure tall,
hence all of its progeny will be tall.
POLLEN GRAINS
TL Tl
TL Vi i TELL
Eae Cr.LLs
Ei f BES BST TTI
pe Ani sSsmiliotneies vend
Phenotypes = 1 TTLL, 2 TTL, 1 TTuw.
Genotypes = 1 7TIl, 2 TTL, 1 TTUl.
EXERCISE 17
Ear-to-Row Test with Corn
Field Practicum
Purpose. — To demonstrate to the student the method of
testing out the transmitting power of individual plants; to
show him how a breeding plot should be arranged for corn; to
teach him how to harvest the corn and make notes on which
to base his selections. A practical demonstration of the method
of pure line selection.
Materials. — For each student a sack for holding ears, wired
tags and strings for tying sacks, and sheets for taking data. A
wooden rack with spikes for drying ears of corn. Grocery scales
for weighing the ears from each row.
446 Plant-Breeding
Data SHEET FOR CORN SELECTION
(Kar-to-Row Method)
Mark Dent (+); mark Flint (V).
No. of row
Total no. of hills
Total no. of stalks
No. barren stalks
Total no. of ears
Total wt. of ears
No. mature ears
Wt. mature ears
No. immature ears
Wt. immature ears
Percentage mature ears
Percentage immature ears
Choose 10 of the best-looking ears from one row on which to
take the following data :—
Wt. of ears
Length of ears
Circumference ! of ears
No. of rows per ear
Wt. of shelled corn
Wt. of cob
A field plot planted by the ear-to-row method, saving unused
half of each ear for comparison with its progeny. It should
contain two or more rows, as space permits, for each student.
Each row should contain 50 hills. The rows should be planted
1 Circumference should be measured at a point about 3 of the distance
from the butt toward the tip.
Appendix E 447
and cultivated under regular field conditions. Two buffer rows
should be planted completely around the plot. These should
be cut and discarded before the interior rows of the plot are
studied. Their purpose and use should be explained to the
class.
Program. — After the instructor has explained the purpose of
the practicum, and the manner of procedure for the afternoon,
the class may be taken to the field. Each student should have
one or two rows for himself. Students may be permitted to
work in pairs, if desirable. Careful and detailed notes should
be made on each row and recorded on data sheets provided for
that purpose. The corn may be taken back to the laboratory
for weighing. Statistics for the whole plot should then be
compiled, so that the individuality of different rows can be
compared. The student should select 10 of the best ears from
each of his rows and put them on the drying rack provided.
These ears are to be used later for a study in the laboratory.
EXERCISE 18
Corn-judging
Students of plant-breeding should be trained to have a critical
judgment of agricultural and horticultural plants. Exercises
in comparative judging are the best way to attain this end.
Utility should be kept constantly in mind.
Details of corn judging will not be given here; they are too
well known to need emphasis. For the East, both dent and
flint varieties should be used. The ears which are judged in
this exercise may be the ones the student himself has previously
harvested from the ear-to-row plot. The best ten ears should
be used for Exercise 19, which should always accompany exer-
cise 18.
Object. — To encourage critical judgment of corn and, by the
same means, of other crops.
448 Plant-Breeding
Materials. — Ten ears of different races and types of corn to
each student; tape, scales, charts, etc.
Each student should score a sample of flint corn according to
the following score card : —
New England Flint
Points
Maturity and seed condition . . . Release ayy te one 20
Uniformity (or eee of single ears) DNL Tire a OTS 15
Kernels<)47 i oo c.8 Bea a a eae ho! cae Oe 15
Weight of ear . . eRe RSiirs Itc! Soh ines eerie nC aNe 10
Length and proportion Sap te ea ete Ge eae hae iene WEEE, 10
Maps. ies. SPUN AIMS CANE ean Woesiag eC ett 5
BuGtSs: ae: Sat Daa ah bik OE eg cA 10
Sulci (space between rows). Ate Rati irl Biliran 10
GOLOE AO We ne Bg ena ee ae yc ge ed alam ae Mega ae ee)
4G 21] pec gM Se Re AAT er Sey ce wc I 100
EXERCISE 19
Statistical Study of Ears of Corn
This should accompany or follow Exercise 18.
Object. — (a) To study critically and statistically the various
parts of ears of corn. (6) To work up these data by biometrical
methods, drawing curves, and ascertaining mean, standard
deviation, coefficient of variability, etc., for the various parts
of the ear. (c) To illustrate testing for germination.
Materials. — Each student should be given the same ears of
corn which he had for Exercise 18; tapes, scales, etc.
The following form should be filled in by each student : —
Notes. — This should not be merely a mechanical process, but
the student should give each step very careful thought. These
tables are given to assist in organizing the student’s method and
his thinking, but not to replace them. Do not study the method
but the plants. Consider carefully the significance of each step.
Appendix E 449
STUDY OF CORN
Variety: Dent, flint, sweet, pop. (Underline.)
Where grown
(a) Length of ear in em.
(b) Cireumference of ear in em. (3 butt to
tip)
(c) Weight of ear
(d) Number of rows
(e) Cireumference of cob (4 butt to tip)
(f) Weight of shelled corn
(g) Weight of cob
(h) Percentage of shelled corn
(¢) Total number of kernels
(j) Average weight of kernel
(k) Width of kernels in em. (taken at ran-
dom) ;
(1) Compute average width
(m) Length of 50 kernels in em. (taken at
random)
(n) Compute average length
EXERCISE 20
Study of Correlations of Characters in Corn
Use the same data as employed in Exercises 17 and 19. Make
correlation tables by accepted biometrical methods of such
characters as length and circumference; length and number of
grains; weight and number of grains; length and weight ; etc.
Work out correlation coefficients.
Object. — To find out if certain characters are associated so
that a measurement of one will give an indication of the other.
Materials. — Data from Exercises 17 and 19; cross-section
paper.
are!
450 Plant-Breeding
EXERCISE 21
Corn Selection — Laboratory Study
Purpose. —To give the student an understanding of the
qualities that constitute a good ear of corn; to teach the bene-
fits and dangers of cross-pollination.
Material. — For each student: 1 tape measure; 1 scalpel;
1 hand lens; 10 ears of corn selected from a row in breeding
plot; samples of various types and colors of corn. These
should have been shelled and soaked in water for 24 hours pre-
vious to this laboratory period in order to render them easy to
dissect. Cobs of corn bearing mixed kernels to illustrate zenia ;
scales; data sheets; germinator.
Program. — The instructor should first explain the purpose
of the practicum and outline the afternoon’s work. He should
explain the structure of a kernel of corn, calling attention to
the difference between the various types of corn and the ad-
vantage of certain shaped kernels. Fecundation should be
thoroughly discussed, and its effect in causing zenia. Illustrate
with diagrams, charts, and specimens.
Discuss the dangers of mixing varieties by close planting.
The danger of close fertilization and the stimulus resulting from
cross-fertilization should also be discussed.
The advantage and manner of making germination tests
should be explained.
The student should remove 6 kernels from each ear and place
them in the germinator to be examined later, at which time he
should record the percentage of germination.
Questions and problems concerning zenia printed on the
outline sheet should be answered in a written report.
Laboratory Directions for Corn Study
1. Complete taking data on 10 ears of corn. Compare with
remnant half of parent ear. From your data select the best
3 ears for breeding purposes.
Appendix H 451
2. Remove 6 kernels from each ear for germination test,
along a spiral line from 1 inch of butt to near the top, revolving
the ear twice.
3. Draw a typical kernel.
(a) Face aspect.
(b) Side aspect.
4. Make and draw longisections through the middle line
both ways of the kernel, showing the following structures: —
(a) Mass of starch or endosperm.
(b) Crescent-shaped body, the germ or scutellum near the
smaller end of the grain.
(c) Remaining portion of embryo lying in the depression
between scutellum and seed-coat.
(d) In sample kernels where does color lie, in the pericarp,
aleurone layer, or endosperm ?
(e) Note relative amount and position of starchy and
horny endosperm in
1. flint kernel,
2. dent kernel,
3. pop-corn kernel,
4. sweet-corn kernel.
5. How would an F;, kernel of corn appear in a cross between
4 g
white sugar x yellow flint?
yellow flint xX white sugar?
white flint X purple flint?
purple flint x white flint?
red sweet X purple flint?
purple sweet x red flint ?
Dominant Characters. —
Colored over white.
Yellow over non-yellow.
452 Plant-Breeding
Red pericarps may conceal purple aleurone.
Purple in aleurone over red in aleurone.
Starchy over non-starchy.
EXERCISE 22
A Study in Potato Selection
Purpose. — 1. To teach the essential characteristics of a good
tuber and a good tuber-line.
2. To teach the principles of selection by a study of variability
in pure tuber-lines.
3. To demonstrate the tuber-unit method of potato selection.
4. To study variability by means of biometrical data, and
the interpretation of constants and curves derived therefrom.
5. To fix in mind how the hills of different weights look.
6. To calculate the theoretical weights per acre when given
certain weights per hill.
First Exercise
Materials. — Printed directions and sheets for recording data.
Manila paper bags, size 12, for containing product of each hill.
Cloth bags for carrying a number of these small bags when filled.
A breeding plot planted by the 4-hill tuber-unit method,
that is, each four hills having the same progeny-number should
come from the same mother tuber, and they should be planted
and staked so that the progeny of each hill and unit can be
distinguished.
This plot should be planted in good soil and given excellent
care throughout the season as its usefulness to the class will
depend entirely on the condition of the crop at harvest time.
The rows and tuber-units should be labeled carefully and accu- °
rately in a convenient way, so that they may be made an object
lesson in record-keeping.
453
Appendix EH
454 Plant-Breeding
Enough hills should be provided so that each student may
have for himself several tuber-units. Five to ten units to each
student will be enough if the student is required to observe and
compare a large number as they lie in the field. The complete
data for the whole field should be compiled by the class as a
whole, and distributed to each student for a comparative study.
Program. — Just prior to the exercise, each hill should be
dug carefully and the tubers replaced where they grew, but
exposed to sight, especial care being taken that no labels be mis-
placed nor lost. The class may then be taken to the field.
The instructor should explain the purpose of the exercise, the
principles of pure-line selection as illustrated here, and the
method of planting a potato-breeding plot by the tuber-unit
method. He should give careful instructions for the after-
noon’s work. The class may then examine and compare the
units as they lie exposed in the rows. The instructor should
point out such differences as occur. A certain number of tuber-
units should then be assigned to each student, and he should
be required to take data from these units, as directed on the
printed sheets provided. Such data-taking as involves the use
of apparatus will necessarily have to be postponed until the
following period, when it can be done in the laboratory.
Each student should carefully preserve his tubers properly
labeled for the next laboratory exercise.
Second Exercise
Materials. — Data taken in Exercise 1; the tubers collected
in Exercise 1; scales; paper plates (6 for each student).
Program. — The instructor should first outline the afternoon’s
work. He should explain the qualities that constitute a good
tuber; also how that ideal form, size, and color differ in various
varieties. He should explain a score-card.
The students may now proceed to finish taking the data on
the tubers that they collected at the previous laboratory period.
Appendix EH 455
When the data are complete, they can all be summed up for
each tuber-unit and the units compared.
Each student should next make out a score-card embodying
the points of his ideal unit, and score his units by it. The
instructor may now give out a score-card by which the whole
class may score their units alike.
Make up hills weighing 3, 1, 14, 2, 3, and 4 pounds, and
draw them natural size.
Compute the yield per acre from the above weights per hill,
assuming the hills to be planted in rows 3 feet apart and 18
inches apart in the rows. One bushel weighs 60 pounds.
Directions for Report on Potato Selection
1. Distribute the data for the number of tubers per hill into
classes.
2. Determine the mode, modal coefficient, mean, standard
deviation, coefficient of variability, and their probable errors for
the number of tubers per hill.
3. Determine the mode, mean, standard deviation, and co-
efficient of variability for the number of marketable tubers per
hill, weight of tubers per hill, and weight of marketable tubers
per hill.
4. Draw Quetelet curve, showing frequency distributions for
number of tubers per hill, number of marketable tubers per
hill, weight of tubers per hill, and weight of marketable tubers
per hill.
5. Distribute into classes the data for the number of tubers
per four-hill-unit, number of marketable tubers per four-hill-
unit, weight of tubers per four-hill-unit, and weight of market-
able tubers per four-hill-unit.
6. Draw Quetelet curves, showing frequency distributions for
number of tubers per four-hill-unit, number of marketable tubers
per four-hill-unit, weight of tubers per four-hill-unit, and weight
of marketable tubers per four-hill-unit.
456 Plant-Breeding
7. Make a transmission curve from the data on the accom-
panying sheet. Which progeny units would you select for breed-
ing purposes? How do you account for the apparent discrep-
ancies which occur, such as the cases where the offspring give a
very different yield from their parents ?
8. Taking into account the number of tubers per hill, weight
of tubers per hill, number of marketable tubers per hill, and
weight of marketable tubers per hill, select the best 25 four-
hill-units. Tabulate these, giving their progeny number and
data for number of tubers per four-hill-unit, number of market-
able tubers per four-hill-unit, weight of tubers per four-hill-unit,
and weight of marketable tubers per four-hill-unit.
9. Give briefly your reasons for selecting the above four-hill-
units. Draw Galton curves for these 25 four-hill-units, showing
variation in the number of marketable tubers per four-hill-unit
and weight of marketable tubers per four-hill-unit.
10. Determine the possible yield of marketable tubers from
an acre of the highest and lowest yielding of the 150 four-hill-
units, also for the highest and lowest and for the average of the
25 selected units.
11. Give a short summary of results as shown by the con-
stants and curves and their bearing on your final selection.
12. Give direction for starting a potato breeding-plot.!
Potato Data for making a Transmission Curve
The following data have been obtained by the method out-
lined above. They represent the weights in grams of parent
hills and the average weight of their corresponding progeny.
The parent hills have been listed in the order of their weight
from lowest to highest (forming a Galton curve).
1 Reference: H. J. Webber, ‘‘Plant Breeding for Farmers.’’ New
York Agr. Exp. Sta., Cornell University, Ithaca, N. Y., Bull. 251:
162-171, 1908.
Appendix E 457
Nos PARENTS PROGENY || Nos. PARENTS PROGENY
1 1077 1463 26 1588 1454
2 1106 1080 eae 47 1588 1615
3 1106 1240 28 1616 1175
4 1361 1881 29 1616 1575
5 1361 837 30 1644 1775
6 1361 1136 31 1644 1807
Z 1361 1536 32 1644 1917
8 1361 1605 33 1758 2250
9 1361 1660 | 4 1814 1660
10 1361 1800 39 1871 1275
11 1361 1895 Lek oo 1871 1: 80
12 1389 1972 Lala SN 1871 1665
13 1418 1696 WORE cs: 1871 1688
14 1418 1904 le ao 1871 1750
15 1471 1440 fay AO 1874 1555
16 1474 1086 41 1874 1861
Lig 1474 1215 42 1874 1889
18 1474 1480 43 1928 1440
19 1531 (ee: 44 1928 1481
20 15a8 1294 45 1928 1620
21 1531 1574 46 1928 1982
22 1531 1725 eae: 274 1984 1575
23 1531 1755 he 48 2041 1236
24 1588 1320 | 49 2041 1880
25 1588 1365 one ses) 2098 2365
EXERCISE 23
Study of Citrus Hybrids
Object. — (a) To study the possibility of obtaining valuable
kinds of citrus fruits by means of hybridization. (b) To study
the structure of citrus hybrids as compared with their parents.
(c) To study the economic value of these hybrids.
Materials. — Obtain from some of the extreme southern ex-
458 Plant-Breeding
periment stations, or from nurserymen or growers, samples of
citrus hybrids, such as citranges, tangelos, and the like, and
samples of Citrus trifoliata. Purchase oranges, lemons, grape-
fruits, and tangerines from the fruit stores. Provide also for
each student, or group of students, a glass, spoon, sugar, and
water.
Compare the hybrids with their parents, with special reference
to the following points : —
(a) Fruit — size, shape, color, amount of juice, quality of
juice, condition of segments, etc.
(b) Trees (if branches or photos are available) — size, shape,
branching, kind of leaves, etc.
(c) General — length of season, resistance to cold, ete.
Squeeze out the juice from several fruits, add sugar and water,
and test the adaptability for beverage and other economic
purposes.
EXERCISE 24
Study of the Results of the Plant-to-Row Tests of Wheat, Oats,
Cabbage, Onions, or any Crop where Data are Available
EXERCISE 25
Studies of Origin of Varieties — Corn, Wheat, Apples, Plums,
Grapes, Etc.
Literature study of the history of varieties. Methods em-
ployed to originate varieties should be carefully noted.
EXERCISE 26
Field Trip to Experimental Grounds
Most experiment stations have plant-breeding experiments
under way, and if a fall inspection of the plats would be in-
structive to students, they should be taken on such a trip early
Appendix HK 459
in the fall and required to make careful notes, to be written up
later in the form of a report.
EXERCISE 27
Working Plans for Practical Breeding Experiments
Object. —'To familiarize the student with field methods of
breeding plants.
Outline for Timothy Breeding
First Year. — Select 10 heads of timothy and grow 50 plants
from each.
100 ft.
10 rows.
4O ft 500 plants in 10 rows 100 ft.
; long. Plants 2 ft. apart in
the rows.
Second Year. — Cultivate.
Third Year. — Choose several of the best plants from the best
two rows, and the one best plant from each of the other rows —
14 or 15 in all. With the seed from these, plant a “test plat,”’
and plow up the original seedling plat.
60 ft.
15 rows.
60 ft. Rows 4 ft. apart — plants 2 ft.
apart in the rows.
Fourth Year. — Cultivate the test plat.
Fifth Year. — Choose 2 or 3 or more of the best rows and save
separately the seed from each. Plow up the remainder of the
rows and plant to vegetables.
460 Plant-Breeding
60 ft.
4 selected rows.
Plant }% acre multiplication
plat from each select row.
60 ft. Seed them broadcast at the
rate of 16 pounds per acre.
Remainder of the plat utilized
for vegetables.
Sixth Year. — Use seed from multiplication plats to plant a
fairly large-sized field. | Continue selection of seedlings, if de-
sired, from select rows according to above scheme.
Outline for Selective Breeding of Timothy
First Year. 1. Manner of procuring seed from starting a selec-
tion. — When timothy is ripening, go over a field and choose a
number of good ripe seed-heads from tall, robust culms which
appear to come from good plants. Also look for exceptionally
good plants from along the roadsides and fences, and whenever
they are found, preserve good heads for seed. Choose good seed-
heads from at least 10 or 12 of these good plants. Thresh the
seed from these heads, keeping the seeds from each plant sepa-
rate, and sow them immediately. No time should be lost.
2. Planting the seed. — The seed should be planted early in
August. Take small boxes about 2 feet long by 13 feet wide
and 4 inches deep; fill them with good soil from some locality
where there has been no timothy and thus where there is little
likelihood of timothy seed being in the soil. Pack the soil down
slightly in the box and smooth off the top, removing all lumps.
Plant the seed in the boxes in short rows, placing the rows about
2 to 24 inches apart. In planting the seed open shallow furrows
in the soil and sow the seed by hand, arranging so that the seed
will be only very lightly covered. Sow the seed as thinly as
possible in the rows and thin out later so that the plants will
Appendix E 461
stand about 1 inch apart. Sow enough seed in rows of sufficient
length, so that when properly thinned there will remain about
300 plants. If thinned to 1 inch apart, this will require rows
aggregating 25 feet long. Be careful to keep the seeds from
each head or plant separate from one another and plainly labeled.
After the seed is sown, water the seed boxes carefully, using a
fine spray, in order to prevent washing the seed out. A good
method is to cover the soil with an open mesh cloth, such as
cheese cloth, and sprinkle the water on this until the soil is
thoroughly wet.. Then place the seed box in the shade in a moist
place, such as the north side of the house. It is a good practice
to keep the boxes covered with paper or glass, until the young
plants begin to appear. It is important to keep them moist at
all times. When the young plants are well up, thin them to
about one inch apart in the rows, leaving the strongest plants.
The plants should be kept in boxes until about the 20th of
September, when they should be planted in the field. About a
‘week before transplanting they should be gradually exposed to
the full sunlight in order to harden them up. At this time each
plant should have 2 or 3 leaves, 3 or 4 inches long.
3. Transplanting into the field. — Choose a place in the field
where the plants may remain for at least two years without
being disturbed. Set the plants two feet apart in rows that
are four feet apart. By this method the greater part of the
cultivation can be done with a horse cultivator. In transplant-
ing the seedlings from the boxes, a time must be chosen shortly
after a rain, when the soil is well moistened. The plants should
be set out about the 20th of September, if possible, so that they
may become well rooted before winter comes on. It may be
necessary to hoe them before winter, but this is not likely if the
land is well prepared before planting.
If 10 heads were originally chosen and 50 plants are grown
from each head, there should be 10 rows 100 feet long, which
would occupy a piece of land 40 x 100 feet.
462 Plant-Breeding
4. Second Year. Cultivating the seedlings. —In the spring
the seedlings must be cleaned out very early before they are
hidden by other grasses. The cultivation and hoeing must be
done at sufficient intervals to keep the ground free from weeds
and in good condition. These plants will produce a few culms
each the first summer, which should be cut as soon as they have
bloomed, in order that the strength shall go into the general
growth. Do not attempt to select the best plants the first
season. A safe judgment cannot be rendered until the second
season.
5. Third Year. Selecting the best plants. — When the plants
reach the stage for cutting in the second summer, that is, when
they are in full bloom, the final selection of the best individuals
can be made. Examine each row critically in order to determine
which head or heads have given the best progeny as a whole.
If any one or two rows are markedly superior to the others,
choose several of the best plants in each of these rows. Also,
choose the one best plant in each of the other rows.
6. Testing the selected plants as clonal varieties. — In order to
make a further test of the 14 or 15 best plants, choose another
uniform plat of fairly good soil between the 5th and 20th of Septem-
ber and prepare for planting an area of slightly over 60 feet square.
This plat should be located at some distance from any other
timothy, preferably 200 to 300 feet. Dig up each selected
plant; divide it into slips or clons and plant this new plat with
them as before, in rows 4 feet apart. Plant one row with slips
from each selected plant, placing the plants 2 feet apart in the
rows. Transplant about 30 slips from each of the selected
plants, so there will be a single row from each about 60 feet long.
This plat may be designated as “the clonal test plat.”
As soon as this clonal test plat is planted from the selected
plants, the seedling test plat may be plowed up and used for
other purposes. .
7. Fourth Year. Cultivation of ‘‘clonal test plat.’ — The
Appendix EH 463
clonal test plat should be cultivated and hoed sufficiently to
keep the weeds down and to allow the full development of the
plants.
8. Fifth Year. Selecting the best clonal rows. — When the
plants are well headed and are about to begin blooming, the
final examination can be made. Go over each row carefully,
and examine it with reference to yield and desirability of type,
and select the superior row or rows. It will be best to retain
at least 2 or 3 of the best rows; or more, if there is but little
difference in them. Good early-maturing and late-maturing
rows should be retained if both are present in the test plat.
When this selection has been made, cut the crop on the dis-
carded rows immediately so that the pollen from these dis-
carded rows will not contaminate, by cross-fertilization, the seed
which is being developed in the selected rows. At any con-
venient time these discarded rows may be dug up and the space
filled with new plants grown from cuttings of the chosen plants.
By a little care and cultivation these select rows can be retained
5 or 6 years as a source of supply of seed of a superior kind. As
the rows of selected types begin to run out, or become impure
by ordinary timothy plants around them, or by other grasses
erowing in the clumps, other or more extended clonal rows
could be planted from them.
9. The multiplication plat. —'The seed from the select rows
of the clonal test plat should be sown in the early fall, sometimes
before the 15th of September in broadcast plats, as large as the
amount of seed obtained will permit. Sow these plats, at the
rate of about 16 pounds to the acre. _ There should be enough
seed from each row to plant about § acre.
Sixth Year. —The seed from these broadcast multiplication
plats can be utilized the next year to plant a fairly large field
which, if desired, may be harvested for seed to plant still larger
areas. These plats may be utilized for seed for several years
before they run out.
464 Plant-Breeding
10. Continuation of the selection. — If the farmer has in mind
the continuous selection of his seed, with the view of selling his
seed as improved seed, he should plant small samples of seed
from each of the selected rows in the clonal test plat. Their
treatment and subsequent selection should be a repetition of the
original scheme outlined above.!
General Directions and Questions for Report on Corn
Breeding
Suppose you buy a farm of 200 acres on which are growing
the following crops: potatoes, corn, timothy, and one of the
three cereals, wheat, oats, or barley. There are 50 acres of
pasture and woodland. You wish to continue growing these
same crops, and at the same time to improve them by a scheme
of selective breeding. Plan the arrangement of fields and breed-
ing plots for the first 6 years, using the following directions.
Timothy breeding plots should be 200 to 300 feet from any
other timothy. Corn plots 1200 feet from any other corn.
(Why?) Each year should be planned separately, using
maps and diagrams, but should be included in a definite
six-year scheme. Observe proper rotations for crops where
desirable.
1. In selecting plants for breeding purposes, why do we choose
individual plants?
2. In breeding work, why do we test out the selected individ-
uals by breeding each one separately ? |
3. Why is it most satisfactory for the breeder to work with
plants that are self-fertilized ?
4. Why do we plant border rows around breeding plots?
5. Why do we detassel alternate halves of adjacent rows in
corn breeding plots?
1 For more detailed directions for timothy breeding, see Webber, H. J.,
‘*Production of New and Improved Varieties of Timothy.’ Cornell
University Agr. Exp. Sta. Bull. 313, 1912.
Appendix E 465
6. Why should corn breeding plots be isolated? What is a
safe distance?
7. Why should timothy breeding plots be isolated? Whatisa
safe distance?
8. Is it necessary to isolate breeding plots of the small cereals?
9. In selection work, what three rules should the breeder
follow who understands the principles of pure-line breeding?
Scheme for Potato Breeding Plots!
First Year. — Choose 500 good tubers. Plant them in a
breeding plot by the tuber-unit method. Rows should be 3
feet apart, hills 1} feet apart in the rows. At harvest time
choose the best 50 units. Save the best 10 from each of these
units for planting a breeding plot the next year.
Second Year. — Plant the selected tubers in a breeding plot
as in the first year. At harvest time discard all poor units.
Select the best 50 units. Save 10 of the best tubers from each
of these units for planting the third year’s breeding plot. Use
the rest for planting a field crop the next year.
Third Year. — Use these 500 tubers to plant a breeding plot.
Plant your field crop with the remaining choice tubers. How
1 For details of the following schemes read Cornell University Exp.
Sta. Bull. 251, ‘‘ Plant Breeding for Farmers,’’ 1908 ; also Bull. 313, ‘‘ The
Production and Improvement of New Varieties of Timothy.”
For cotton breeding, see Webber, H. J., ‘‘Improvement of Cotton by
Seed Selection,’’ U. S. Department of Agr. Yearbook, 1902, pp. 365-
386.
16.5 ft. = 1 rod; 160.0 sq. rd. = 1 acre.
Plant: Corn, 8-12 qt. per acre; Oats, 2~3 bu. per acre; Wheat,
2-3 bu. per acre; Barley, 2-3 bu. peracre; Potatoes, 12—15 bu. per acre;
Timothy, 6-8 qt. or 16 lb. per acre.
Standard weights: Corn, 1 bu. = 70 lb. shelled, or 56 lb. on cob;
Oats, 1 bu. = 32 lb.; Wheat, 1 bu. = 60 lb.; Barley, 1 bu. = 48 lb.;
Potatoes, 1 bu. = 601lb.; Timothy, 1 bu. = 45 lb.
Average yield per acre in United States for 1902: Corn, 20.2 bu. ; Wheat,
£5.95 buy.; moe 37.4 bu.; Barley, 50.4 bu.; Potatoes, 113.4 bu.
H
466 Plant-Breeding~
large a field can be planted if the yield has been at the rate of
200 bushels per acre?
Fourth and Subsequent Years. — Continue this same scheme,
constantly discarding the poor units and selecting the best for
breeding.
Estimate how large your breeding plot should be in order to
supply a 5-acre field with seed in the third year, supposing the
yield from your selected units to be the same as the average
yield given by the 25 best selected units in your former report,
1.e. about 370 bu. per acre.
Scheme for Corn Breeding Plots
All corn breeding and increase plots should be at least 1200
feet from any other corn. Why?
First Year. — Select from the field 100 ears. From these
choose the best 50 for planting a breeding plot the next year.
Second Year. — From these 50 ears, plant a breeding plot
by the ear-to-row method. Rows should be 4 feet apart, hills
3 feet apart in the row, each row to contain 100 hills. Surround
the breeding plot with 2 or more border rows planted with seed
from the unused select ears. Why? Detassel alternate halves
of adjacent rows. Why? Select from the best 10 or 12 rows
50 to 100 of the best ears, choosing the best 50 for the next
year’s breeding plot. Save the seed from the other best-yielding
rows for an increase plot, or the general field.
Third Year. — Plant your breeding plot as before, with the
best selected 50 ears. With the other selected ears plant an
increase plot or general field. Select as before the best 50 ears
from the breeding plot for the next year’s breeding plot, saving
the remainder for a new increase plot. Save ears from this
year’s increase plot for planting next year’s field.
Fourth and Subsequent Years. — As before, plant your breed-
ing plot, increase plot, and field, using a continuous and pro-
gressive scheme of selection.
Appendix E 467
Scheme for Wheat Breeding Plots
First Year. — Choose 100 fine heads for starting your improve-
ment work.
Second Year. — Plant seed from these select plants in short
rows by the plant-to-row method. Space the rows 1 foot apart.
Select a few rows, say twenty, to furnish seed for a breeding plot
in the third year.
Third Year. — Plant seed from each of these select rows in a
breeding plot. Do not mix the seed from different rows. Plant
as many 17 foot rows in each plot as the amount of seed saved
will permit. This is at the rate of 1} bushels per acre. The
rows should be 1 foot apart.
Fourth Year. — Find average yield of progeny rows that came
from the selected rows of the third year. Select several of the
best strains which may yield about 24 bu. per acre. With this
seed plant increase plots from each kind of seed. Save seed from
2 or 3 of the best yielding plots for more extensive trials in the
5th year. The rest of the seed can be used for planting a field.
Make new selections of heads in the fields and repeat the whole
program as before. There may be many more valuable types
in the fields that can thus be isolated.
Fifth Year. — Test out your select strains and choose one or
two of the best for increase plots and for planting your field.
Plant the field this year with seed from last year’s increase plot
and from the test rows.
Scheme for Oat or Barley Breeding Plots
The principles of selection and methods of breeding these
cereals are the same as for wheat.
INDEX
Absence tactors, 192.
Acquired characters, 17.
Adami, M., 145.
Adams fund, 314.
Adam's laburnum, 142.
Adaptation, 7, 37, 106.
Alfalfa, 313.
Alkali resistance, 313.
Allelomorph, 325.
Allen, Dr., 314, 315.
American Seed Trade Association,
309.
Anemone coronaria, 57, 58.
Animals, breeding, 217.
Anthers, 276.
Anthocyanin, 186.
Antirrhinum (see snapdragon).
Apples, 212, 255, 295; hybrid, 235.
Arthur, 228, 239.
Artificial selection, 37.
Asexual propagation and hybridi-
zation, 125.
Asparagus, 313.
Associations, plant-breeding,
Atavism, 211, 231.
Average deviation, 47.
300.
Barker, E. E., 394.
Bartel, T. C., 254.
Barteldes, 264.
Bateson, 155, 183, 187, 192.
Beans, 260; Emerson’s experiments
with, 189.
Bibliography, 335.
Biometry, 41, 325.
Biotypes, conception of, 19.
Blackberries, hybrid, 136.
Blackberry, 253.
Books, plant-breeding, 328.
Braun, Alexander, 20.
‘‘Breaking the type,” 22, 219.
Breeding periodicals, 332.
Breeding plants, rules for, 222.
Broughton, Mr., 91.
Browne, Dr. Thomas, 56.
Bruant, 237.
Brunella vulgaris, 80.
Brussels sprouts, 243.
Budd, Professor, 258.
Buds, methods of emasculation,
291.
Bud-selection, 39, 242.
Bud-sports, 210, 241.
Bud-variation, 11, 29.
Bud-varieties, 242.
Burbank, 112, 321.
Burpee, 264.
Burr, ‘‘Field and Garden Vege-
tables,’’ 295.
Cabbage, evolution of, 267; savoy,
244; shapes, 245; wild, 240.
Camerarius, 110.
Canadian Seed Growers’ Associa-
tion, 304.
Cannas, 237, 265.
Capsella Heegeri, 80.
Carex, little natural crossing in,
103:
Carnation, 179.
Carriére, 58, 223, 239, 296.
Castle, 180.
Cauliflower, 248.
Cavalier, wheat, origin of, 91.
469
470
Cereals, disease-resistant, 313.
Change, of seed, 28 ; of stock, results
from, 105, 107.
Chelidonium, 55, 56.
Cherries, hybrid, 235.
Chimera, 146, 148.
Chromoplasts, 186.
Chromosome, 325. :
Chrysanthemum, 251, 252, 2538,
256, 257, 258, 259, 262, 263, 264,
267, 268, 269; carinatum, 226;
indicum, 250; tnodorum plenis-
simum, 87 ; morifolium, 249 ; sege-
tum, 86, 89; segetum plenum, 86,
88.
Citranges, 132, 312.
Citrus trifoliata, 312.
Climate, as factor in variation, 25,
26; man’s control over, 27.
Coefficient of heredity, 152; of va-
riability, 49.
Collard, 242.
Color, mendelian inheritance of, 185.
Commercial breeding agencies, 308.
Composit, 223.
Compositous flowers, 279.
Corn breeding, 216.
Correns, 155.
Cotton, 213; 214, 312.313:
Council of grain exchanges, 310.
County agent, the, 310.
Cowpeas, disease resistance, 220.
Cross, function of, 101, 230.
Crosses, characteristics of, 123.
Crossing, a means not an end, 232;
and change of seed, 103; effects
on the species, 97; from stand-
point of plant improvement, 108 ;
how to overcome antipathy to,
121; limits of, 97,98, 99; process
of, 281; refusal result of natural
selection, 100; vigor as result of,
ee Lass.
Crossing animals, 216.
Crossing plants, philosophy of, 92.
Crozy, 237.
Index
Cucumber pollinations, 141.
Cultivation, philosophy of, 24.
Cupid sweet pea, 77.
Curled kale, 241.
Cytisus Adami, 142, 145.
Darwin, 20, 34, 52, 59, 73, 105, 107,
111, 113, 209, 240, 242, 244, 296,
307.
Dates, 313.
Davenport, C. B., 183.
Davenport, E., 149.
Davis, Bradley Moore, 318.
Deviation, average, 47 ; standard, 48.
de Vries, Hugo, 52, 53, 59, 62, 63,
U2 CO, e, 1055 LO ao:
Dewberry, 253.
Dihybridism, 171.
Dicecious flowers, 278.
Disease resistance, 219, 220, 313.
Dominance, 165; incomplete, 179.
Dominant characters, 325.
Dorsey, M. J., 424.
Double flowers, experiments in
production of, 86; history of
appearance of, 56.
Downing’s ‘Fruits and Fruit
Trees,’ 295.
Draba, 73.
Drought-resistant plants, 313.
Duggar, B. M., 318.
Duplex, 325.
Durum wheat, 313.
Ear-to-row, 308.
East, E. M., 318.
Eckford, 237.
Egg-plant, 128, 141.
Egyptian cotton, 313.
Elderberry, 217, 218.
Elementary species, 63, 80.
Emasculation, 282.
Emerson, 189.
Environment as a cause of varia-
tion, 16, 216:
Epistatic, 325.
Index
Error, probable, 50.
Evening-primrose (see QCinothera).
Evening-primroses, laws of muta-
bility of, 72.
Factor hypothesis, 326.
Fairchild, Thomas, 110.
Fertilization, 270.
Flowers, structure of, 270.
Fluctuating variations and muta-
tions, 54.
Focke, 232.
Food supply, as cause of variation,
20, 21; of different branches, 23.
Frequency curve, 42.
Fultz wheat, origin of, 91.
Galton curve, 326.
Gametes, 168, 326.
Garden varieties, origin of, 18.
Gartner, (C. &., 110; 111.
Genetics, 326.
Genotype, 326.
Germ-plasm, action of environ-
ment upon, 17.
Gibb, 258.
Gideon, Peter M., 233.
Gladiolus, 237.
Glossary, 325.
Gmelin, J. G., 110.
Goff, 228, 229.
Gold Coin wheat, origin of, 91.
Gourds, 140.
Graft-hybrids, 142.
Grain exchanges, council, 310.
Grapes, 212, 235; hybrid, 133.
Gray, Asa, 35.
Green, Ira W., 91.
Hallock & Son, 247.
Harper, R. A., 318.
Head-to-row, 308.
Helianthemum, 73.
Henderson, 264.
Heredity, 149; coefficient of, 152. ;
studied collectively, 149.
Aga
Heterozygote, 326.
History of mutation, 55.
Homozygote, 326.
Hopetown wheat, origin of, 91.
Hurst, 192.
Husk-tomato pollination, 141.
Hybridization and asexual prop-
agation, 125.
Hybridized, what plants can be,
I ke
Hybrids, 326 ; history of, 110 ; defini-
tion of, 108; influence of sex on,
138; production of, 101; vari-
ability of, 122.
Hyper-chimera, 148.
Hypostatic, 326.
Ideal, 220.
Illinois Seed Corn Breeders’ Associa-
tion, 303.
Immature seeds, 228.
Implements of pollination, 292.
Improvement of plants, systematic,
295.
In-breeding, 127.
Indeterminate varieties, 209.
Individuality, fact of, 2.
Individual selection, 308.
Inhibitor, 180.
Inter-crossing, swamping effects of,
98.
Ipomeeas, 229.
Kinshu rice, 313.
Knight, Thomas Andrew, 110.
Kohl-rabi, 248.
Kolreuter, J. G., 110.
Kumerle, J. W., 265.
Laboratory exercises, 394.
Lamark, 59.
Lemoine, 237.
Lettuce, improvement in, 221.
Linaria vulgaris (see toad-flax).
Linaria vulgaris peloria, 84.
Linnezus, 110, 138.
472
Locke, 180.
Lupines, 231.
Maize, 224.
Mass selection, 307.
Mean, 45; use of, 46.
Measurement of, 41.
Mendel, 155.
Mendelian inheritance of color, 185.
Mendelian ratio, 179.
Mendelism, application to plant-
breeding, 202, 225 ; in wheat, 194;
limits of, in the production of
new varieties, 204; of tomatoes;
203; summarized, 200.
Mendel’s experiments, 156.
Mendel’s law, explanation of, 158.
Methodical selection, 307.
Minnesota Field Crop Growers’ As-
sociation, 303.
Mirabilis, 112.
Modal coefficient, 45.
Mode, 44.
Moncecious flowers, 277.
Monotypic genera, 224.
Moore, Jacob, 235.
Morning-glories, Darwin’s experi-
ments with, 114.
Morse & Company, 77.
Morus multicaulis, 299.
Munson, Professor, 117, 235.
Munting, Abraham, 57.
Mutability, laws of, with evening-
primroses, 72.
Mutants, how produced
garden, 71.
Mutation, history of, 55; first use
of word, 56.
Mutations, 40, 52, 326; economic
significance of, 90; and fluctua-
tions, 54; can they be produced
artificially ? 200 ; examples of, 76;
experimental study of origin of,
84 ; frequency of occurrence of, 79 ;
mutations resulting from men-
delian segregation and recombi-
in the
Index
nation, 198; mutations which
mendelize are constant, 193.
Natal and post-natal variations, 18.
Natural hybrids, rarity of, 102.
Natural selection, 34, 93; as cause
of variation, 14.
Navel oranges, 313.
Nectarines, 241.
New York Plant Breeders’ Associa-
tion, 304.
Nicotiana pollinations, 142.
Nilsson, Professor, 304.
Nulliplex, 326.
Oats, Swedish select, 313.
CGncthera albida, 63, 67, 71, 74;
analytical table of seedlings,
68-69; brevistylis, 63, 64, 71, 74;
de Vries’ experiments with, 59;
elliptica, 64, 68, 71, 74; gigas,
63, 65, 66, 71, 74; levifolia, 63,
64, 71, 74; Lamarkiana, 59,
61, 64,71; 74 > \hlata-64 or
74; muricata, 60; nanella,
63, 64, 71, 74; oblonga, 63,. 67,
71, 74; rubrinervis, 63, 65, 71,
74; scintillans, 64, 68, 71, 74;
variations in stature of, 53.
Ohio Plant Breeders’ Association,
304.
Olives, drought-resistant, 313.
Ononis repens, 80.
Organs, essential, 274.
Orton, 313.
Palmer, Asa, 264.
Peaches, 212.
Peas, Mendel’s experiments with,
Lome
Pedigree culture, 308.
Pelargoniums, 237.
Peloric toad-flax, 79.
Pepino pollination, 141.
Pepper pollinations, 141.
Peppers, 222.
Index
Perennial plants, 241.
Periclinal chimera, 148.
Periodicals, breeding, 332.
Phenotype, 327.
Physalis, 104.
Pineapple hybrids, variation of, 123.
Pistils, 27 Pf.
Plant-breeding: associations, state,
300; books, 328; by selection,
218; defined, 212; forward
movement in, 294; instruction,
32> Iaboratory, U.S.’ Dept:
Agri., 311; projects, 315; use
of term, 296.
Plant improvement a serious busi-
ness, 298.
Plant introductions,
Sue:
Plants, differences compared with
animals, 10.
Plant-to-row, 308.
Plateation, 397; defined, 327.
Plums, 212, 294.
Pollen, 280.
Pollen storage, 289.
Pollination, 270; process of cross,
281, 289; uncertainties of, 140.
Poncirus trifoliata, 312.
Population, 41.
Potatoes, 241.
Presence-and-absence
181.
Pride Butte wheat, origin of, 91.
- Probabilities, theorem of, 169.
Probable error, 50.
Punnett, 183, 184.
division of,
hypothesis,
Quetelet curve, 44.
Radishes, division of, 239.
Raspberries, hybrid, 235.
Recessive characters, 327.
Recessiveness, 165.
Regel, cited, 295.
Reproduction, difference between
plants and animals, 10.
473
Retrograde varieties, 65.
Rogers’ grape hybrids, 235.
Roguing, 251.
Russian apples, 212, 258, 295.
Savoy cabbage, 244.
Score card, use of, 236.
Sea Island cotton, 312.
Sectional chimera, 148.
Seed, change of, 28.
Segregation, 327.
Selection, accumulative, 209; ar-
tificial, 37, 248; individual, 308;
mass, 307; methodical; 307;
plant-breeding by, 218.
Sex, a factor in variation, 15, 215;
influence on hybrids, 138; origin
and function of, 95.
Shirley poppy, 76.
Shull, 190, 318.°
Simplex, 327.
Snapdragon, 83.
Snyder blackberry, 255.
Solanaceous plants, 222.
Solanum darwinianum, 147; Gart-
nerianum, 147 ; graft-hybrids, 146 ;
kélreuterianum, 147 ; proteus, 147 ;
tubingense, 146.
Somatic, 327.
Species, definition, 8.
Species-formation, 8.
Spencer, 105.
Spillman, 180, 194.
Sport, 39.
Sprenger, 55.
Squares, method of, 169.
Squashes, 128, 140.
Stamens, 271.
State experiment stations, 310.
State plant-breeding associations,
302.
Statistical methods (see biometry).
St. Hilaire, Geoffroy, 58.
Stout, A. B., 318.
Struggle for life, a cause of varia-
tion, 30.
474
Sturtevant, 228.
Sugar beets, variation in amount
of sugar in, 54.
Swede turnip, 248.
Swedish Seed Association, 304.
Swedish select oats, 313.
Swingle, Walter, 312.
Systematic improvements of plants,
295.
Tangelo, 133, 312.
Teas’ Weeping mulberry, 233.
Teosinte, 137.
Thomson, 149.
Thymus vulgaris, 80.
Timothy, variability of, 3.
Toad-flax, 79, 81, 82.
Tobacco pollinations, 142.
Lomato, 215, 222. 228; 244, 246:
ignotum, 246; pollinations, 141.
Trihybrid, 177.
Tschermak, 155, 188.
Tuber-unit, 308.
Type, 43.
Unit-characters, 9, 154.
United States Dept. Agri., 310.
Uses, breeding for specific, 224.
Variability, biometrical expression
of, 43, 47; coefficient of, 49.
Variation, action of natural selec-
tion upon, 14; and adaptation, 7 ;
causes of, 13, 30, 94; caused by
environment; caused by _ sex
differences, 15; in climate, 25;
choice and fixation of, 34; de
Vries’ classification, 53; fluctuat-
ing, 54; in food supply, 20;|
Index
measurement of, 41; natal and
post-natal, 18.
Varieties, ‘‘coming true,”’ 210, 211;
how they originate, 209; inde-
terminate, 209; non-uniformity
of, 19; outright production of,
by. crossing, 118; retrograde, 63 ;
spontaneous appearance in wild
state, 79.
Variety, what is it? 35.
Verlot, 244, 296.
Vigor as result of crossing, 112, 115.
Vilmorin, 226, 230, 231, 269.
Waitisael 22.
Vries, de, Hugo (sce de Vries).
Walker, Ernest, 243.
Wallace, 105, 123.
Watermelons, wilt-resistant, 219.
Wealthy apple, 233.
Webber, 133, 156, 312.
Weismann, 16, 17.
Wheat, Durum, 313.
Wheatland fife wheat, origin of, 91.
Wheat-rye hybrid, 136.
Wier, DBa-2338:
Wild cabbage, 240.
Wilks, Rev. W., 76.
Willis, 117.
Wilson, strawberry, 248.
Wilt-resistant watermelons, 219.
Winkler, Professor, 146, 148.
Wisconsin Agricultural Improve-
ment Association, 300.
Xanthein, 187.
Xenia, 327.
Zygote, 327.
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