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PLANT-BREEDING

COMMENTS ON THE EXPERIMENTS
OF NILSSON AND BURBANK

BY

HUGO DE VRIES

Ml
PROFESSOR OF BOTANY IN THE UNIVERSITY OF AMSTERDAM

1
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563975.

/. (o- S^

CHICAGO
THE OPEN COURT PUBLISHING CO.

London: Kegan Paul, Trench, Trubner & Co., Ltd.

1907

I2.Z

Copyright by
THE OPEN COURT PUBLISHING CO.

1907

O'

PREFACE

Under the influence of the work of Nilsson, Burbank,
and others, the principle of selection has, of late, changed
its meaning in practice in the same sense in which it is chang-
ing its significance in science by the adoption of the theory
of an origin of species by means of sudden mutations. The
method of slow improvement of agricultural varieties by re-
peated selection is losing its reliability and is being supplant-
ed by the discovery of the high practical value of the ele-
mentary species, which may be isolated by a single choice.
The appreciation of this principle will, no doubt, soon change
the whole aspect of agricultural plant breeding.

Hybridization is the scientific and arbitrary combination
of definite characters. It does not produce new unit-char-
acters; it is only the combination of such that are new.
From this point of view the results of Burbank and others
wholly agree with the theory of mutation, which is found-
ed on the principle of the unit-characters.

This far-reaching agreement between science and prac-
tice is to become a basis for the further development of
practical breeding as well as of the doctrine of evolution.
To give proof of this assertion is the main aim of these Essays.

Some of them have been made use of in the delivering of
lectures at the urtiversities of California and of Chicago
during the summer of 1906 and of addresses before various
audiences during my visit to the United States on that oc-
casion. In one of them (II. D.), the main contents have

VI PREFACE

been incorporated of a paper read before the American
Philosophical Society at their meeting in honor of the bi-
centennary of the birth of their founder, Benjamin Franklin,
April, 1906.

The results of Nilsson have been published only in the
Swedish language; those of Burbank have not been de-
scribed by himself. My arguments for the theory of mu-
tation have been embodied in a German book, " Die Mu-
tationstheorie" (2 vols. Leipsic, Veit & Co.), and in lectures
given at the University of California in the summer of 1904,
published under the title of "Species and Varieties; their
Origin by Mutation." A short review of them will be found
in the first chapter of these Essays.

LIST OF ILLUSTRATIONS

Fig. Page

1.

A. The Oak-leaved Hazelnut (Corylus Avellana laciniata),
a natural sport of the ordinary hazelnut (B) ... 7

2. A. The toadflax (Liimria vulgaris). B, C. Its peloric va-

riety. D. A peloric flower on an ordinary specimen . 12

3. A. The Double-flowered Corn-marigold {Chrysanthemum

segctum plenum), an experimental mutation produced at
Amsterdam, 1899. B. A flower-head of the original cul-
tivated variety. C. The first result of selection. D. The
first sign of doubling. E. A typical double flower-head , 13

4. The Experiment Garden in the botanical garden at Am-

sterdam, covered with iron wire netting. Cultures of
different Evening Primroses, some enclosed in bags for
artificial pollination, 1904 ...... 15

5. Lamarck's Evening Primrose {Oenothera Lamar ckiana), a

mutating species . . . . . ■ ■ 17

6. Leaves of Lamarck's Evening Primrose (A), and of two of

its mutants (B. Oen. lata. C. Oen. scintillans) . . 19

7. Mutants of the Evening Primrose. A. The red-veined

form (O. rubrinervis) which is of the same size as the
original species. B. and C. The dwarfish variety {Oen.
nanella) ......... 21

8. A flower-spike of the giant-mutant {Oenothera gigas), which

originated in my garden, 1896 ..... 23

9. A flower-spike of the red-veined mutant {Oenothera rub-

rinervis), which has been produced almost yearly by the
parent species ........ 25

10. Dr. Hjalmar Nilsson, Director ot the Swedish Agricultural

Experiment Station at Svalof ..... 28

11. Poland wheat (Triticiim polonicum) .... 30

12. A. Belle vue de Talavera-wheat, isolated by Le Couteur.

B. Bearded white wheat, produced by Patrick Shirreff.

C. Squarehead wheat, the most famous production of

th^ same breeder ....... 32

13. A. Hallett's pedigree Chevalier barley. B. Hallett's pedi-

gree wheat ........ 39

14. A reproduction of part of the first advertisement of pedi-

gree wheat by F. F. Hallett. See the Times, London,
June 18, Nov. 8 and Dec. 19, 1862 .... 40

15. The Swedish Agricultural Experiment Station at Svalof.

Part of the campus and residence of the Director . . 49

16. The new building of the Swedish Experiment Station at

Svalof, erected 1907. ...... 53

vii

viii PLANT-BREEDING

Fic.

17. The Laboratory of the Agricultural Experiment Station at

Svalof, Sweden .......

18. The Storage building of the Agricultural Experiment Station

Svalof, Sweden . . - ■ • • •

19. Svalof Concordia pea, a most productive erect new variety

of green peas, produced at Svalof ....

20. Svalof Pearl Summer wheat, not layering, early ripening,

with full-rounded kernels, that keep in the ears at har-
vest time . . . . - ■ • •

21. Ordinary Butt Summer wheat, for comparison with the im-

proved variety of the previous figure ....

22-26. Five different types of new varieties of oats, produced

at Svalof. Fig. 22. Flag-oats

23. Stiff-branched Svalof oats ....

24. Svalof oats with spreading branches

25. Svalof oats with bending branches

26. Svalof oats with weak branches

27. A. Rye of Schlanstedt, produced by Wilhelm Rimpau by

slow repeated selection. B. Ordinary rye .

28. Determination of centgener power of the progeny of individ-

ual wheat plants at the Agricultural Experiment Station
of Minnesota at St. Anthony Park. The progeny of each
parent plant packed in a sack for separate harvesting.
The Director, Mr. Hays in the first carriage, August, 1904

29. Breeding block of corn which has been bred for high oil

content on the farms of Funk Bros. Seed Co., Bloom-
ington, 111. ...... . .

30. Strength of individual stalks of corn on the breeding blocks

of Funk Bros. Seed Co., Bloomington, 111.

31. Different types of corn. A. King Philipp, a variety of flint

corn. B. Giant yellow dent corn. C. Rice popcorn.
D. Dwarf popcorn .......

32. A. Sweet corn, an ear with a staminate upper part and with

some few kernels in top. B, C. Parts of a tassel of flint
corn bearing staminate spikelets and kernels
^T,. A highly ramified ear of corn .....

34. A. A male or staminate spikelet of corn. B. A pair of pis-

tillate or female flowers. After models of Brendel, Berlin

35. A. Tassel of corn, flowering and producing the anthers from

the spikelets. C. Ear in the husks, producing the silks

36. Sweet corn, with scattered starchy kernels, produced by

partial cross-pollination ......

37. jSIethod of sacking ear and tassel in corn for hybridizing,

Agricultural Experiment Station, ISIanhattan, Kansas .

38. The hand pollination of corn in one of the breeding blocks

on the farms of Funk Bros. Seed Co., Bloomington, 111.

39. Another view of hand pollination in breeding blocks of

corn of Funk Bros. Seed Co., Bloomington, 111.

LIST OF ILLUSTRATIONS ix

Fig. Page.

40. Growlli of individual rows of corn on the breeding blocks

of Funk Bros. Seed Co., Bloomington, 111. . . 135

41. Rows from cobs of corn which have been self-fertilized and

from those which have not been self-fertilized. The small
rows are those self-fertilized. On the breeding blocks
of Funk Bros. Seed Co., Bloomington, 111. . . • 139

42. Alternate detasseled rows of corn, at a later period of

growth, on the breeding blocks oif Funk Bros. Seed Co.,
Bloomington, 111 14°

43. View in the experiment garden of Amsterdam, with cul-

tures of corn and Evening Primroses .... 143

44. Twisted stems. A. Of a horsetail {Equisctiim Telmateja).

B. OitheWiXdiediSe]. {Dipsacus sylveslris) . . . 144

45. Sterile Corn, a special form of barren stalks without tassel

and without ear. Originated in the botanical garden at
Amsterdam, 1888 . ...... 145

46. Sweet com. A. With straight rows. B. With oblique

rows ......... 149

47. A kernel of corn cut longitudinally. H, E. Horny endo-

sperm. INI, E. Mealy or starchy endosperm. S Scutel-
lum. G, G. Germ. B. The young bud from which the
stem will develop. R. Rootlet. After Frank . . 153

48. One of the breeding blocks of corn, which is being bred for

high protein on the breeding blocks of Funk Bros.
Seed Co., Bloomington, 111. Sept. 1906 . . . 155

49. Luther Burbank of Santa Rosa, Cal. . . . -158

50. Burbank's farm at Santa Rosa, Cal., showing the residence,

the greenhouse, the shed, and part of the Experiment gar-
den. Photograph of the S. Pac. R. R. Co. . . . 161

51. Experimental garden of Luther Burbank at Santa Rosa.

A spineless cactus is seen along the fence. Cultures of
Echeveria and other species in the foreground. Photo-
graph of the S. Pac. R. R. Co. ..... 163

52. Luther Burbank in the garden before his house at Santa

Rosa, Cal., receiving a visit of the author of these Essays
(in the middle) and of Dr. G. H. ShuU, of the Carnegie
Institution (to the right) ...... 165

53. A field of improved Australian Star-flowers on Burbank's

home farm ........ 169

54. The improved Everlasting Australian Star-flower . .171

55. A Hybrid Walnut reaching double the height of ordinary

trees {Juglans Cal if ornica nigra) . . . -173

56. Extreme variability in the size of seedlings of hybrid wal-

nuts in the second generation . . . . -175

57. A row of hybrid walnuts before the residence of Luther

Burbank at Santa Rosa. Photograph of the S. Pac. R.

R. Co 177

58. Burbank Giant prune . . . . . . •179

X PLANT-BREEDING

Fig. Page.

59. Burbank Sugar prune . . . . . . .181

60. The improved stoneless prune. The pit is not surrounded

by any stony material, but by a jelly .... 190

61. HyVjrid Cactus Seedlings at Santa Rosa, 1904 . . .191

62. The Spineless edible Cactus, a hybrid between wild spine-

less species and the cultivated varieties, growing along

the fence of Burbank's farm at Santa Rosa . . . 193

63. A row of Shasta-daisies ...... 195

64. A flower-head of the fluted variety of the Shasta-daisy . 198

65. The crisp-leaved hyl^rid Heuchera . . . -197

66. The crisp-leaved hybrid Heuchera of Burbank. B, C.

Normal type of Heuchera leaves .... 201

67. Extreme variability in the size of hybrid Callas . . 205

68. A. The plum and B. The brown-leaved Prunus Pissardi,

two species grafted on the same tree . . . -215

69. Seedlings of the Spineless edible Cactus in their first and

second years. Most of them are spiny, but the rare
spineless ones will be selected for propagation . . 227

70. Seedlings of the Spineless edible Cactus in their second year. 229

71. Extreme ' iriability in the shape of the leaves of hybrid pop-

pies. Second generation from a cross between the Bride-
variety of the opium poppy and the Oriental poppy . 231

72. A. The variety the Bride of the opium poppy. B. The

wild species {Papaver pilosum) . C. The hybrid of these

two poppies . . . . . . . .233

73. Flowers of Columbine, showing the spurs . . . 241

74. The deadly nightshade, or Atropa Belladonna. A. Brown

flower, and B. Black fruit of the species. C. A twig of

the yellow variety with pale flowers and yellow fruits . 243

75. The long-leaved Veronica (Veronica longifolia) . . 245

76. The laciniated bramble {Riibiis jruticosiis laciniatus), witli

divided petals. B. A flower of the ordinary bramble . 249

77. A. Ordinary celandine (Cliclidoiiiidn ma jus). B. Lac-

iniated celandine (C. in. laciiiiatiim), which originated
from A in a garden at Heidelberg about 1590. a and b.
Flowers of A and B . . . . . .251

78. Flowers of Evening Primroses, deprived of the petals. A.

The ordinary species {Oen. biennis), a self-pollinating
species collected near Chicago. B. Summer-flower of
Lamarck's Evening Primrose, the stigma protruded be-
yond the anthers. C. A late flower of the same plant
with the anthers touching the stigma . . -252

79. Panicles of oats. A. With erect and B. With spreading

branches ........ 263

80. Svalof Grenadier wheat, the best of the new Swedish varie-

ties of wheat, very productive of grain and straw . . 266

81. Svalof Bore-wheat, a new hardy variety for the cultures of

2vliddle Sweden ....... 267

LIST OF ILLUSTRATIONS xi

Fig. Page.

82. A panicle of oats, with weak branches, photographed at

Svalof, Sweden . . . . . . -273

83. A panicle of oats with stiff branches, photographed at

Svalof, Sweden . . . . . . -275

84. A spikelet of oat-grass {Avena elatior), showing a flower

with two palets, three stamens, and two stigmas (a), a
flowerbud (b), of which only the palets are visible,
and the third or sterile flower (c) . . . .278

85. Barley. A. A complete spikelet with the three flowers.

B and C. Single flowers seen from dilTerent sides, show-
ing two palets, three stamens, and the ovary with the
stigmas. In B, also the two outer scales or glumae. D.
Stamens and ovary of a flower . . . . -279

86. Svalof Solo pea, a new forage-plant, most productive of

seeds and foliage. Leaves green . . . .281

87. Svalof Groppea, a new early ripening forage-plant . . 283

88. The wild oat-grass (Avena elatior), a pasture grass . . 285

89. A pitcher-like leaf of tobacco . . . . .291

90. Pitchers of Magnolia, A, B, C. Of clover, D, E. Of

the lime-tree {Tilia), F, G. One-leaved pitchers.

C. Two-leaved. A. Upper part of a leaf only trans-
formed into a pitcher. D, E. Pitcher-like leaflets of

the ordinary and of the five-leaved clover . . . 293

91. A. Seedling-plants of Evening Primroses. B. Of the fig-

wort (Scrophularia nodosa). C. Of Silene odontipetala.

D. Of poppies. E. Of the beech. A i and D i. Nor-
mal seedlings. A 7, B, C 2, D 4, E, Tricotyledonous
seedlings. C 3, D 5, Seedlings with four and D 6 with
five seed-leaves. A 2-6, C i, D 2-3, Different degrees

of splitting of seed-leaves ...... 295

92. Polycephalous opium poppy. A. Normal fruit. B. The

same cut longitudinally. C, D. Normal stamens. E, F.
Stamens transformed into secondary carpels. G, H, I.
Secondary carpels, cut transversely with one, two, and
four rows of seeds ....... 299

93. Young plant of opium poppy in the sensitive period of the

development of the terminal flower, cut longitudinally.
A. Flower-head of June 7. B. Of June 14. C. All parts
discernible. D. Diagram of flower. E. Diagram of
young flowerbud. P. Petals. S. Stamens . . 301

94. The Double Corn-marigold, an experimentally produced

variety ......... 303

95. Variability in the size of the ripe fruits of the Evening

Primrose of Lamarck. A. A weak plant with small
fruits. B. A tall plant with large fruits . . . 305

96. A. The Pansy and some of its parents. B. Viola lutea

grandiflora. C. Viola tricolor versicolor. D. Viola tri-
color lutescens. After Wittrock . . . -311

xii PLANT-BREEDING

Fig. Page.

97. Gordon's currant (Ribes Gordonianum), a hybrid of the

flowering currant and the golden currant . . . 314

98. A. The flowering currant of the Pacific coast (Ribes

sangiiineiim). B. The yellow currant (Ribes aureum) . . 315

99. A. The cultivated snapdragon. B-G. Its color varieties.

B. Yellow. C. Delila, tube white and lips red. D, E.
Flesh-colored. F. Brilliant, of a fiery red. G. Album,
white with a yellow spot on the lip. H. The calyx and
the style after the removal of the corolla . . -317

100. Danebrog Opium poppy ; petals red with a large white spot

at the base ........ 319

loi. Glass-covered part of the experiment garden at Amsterdam
in the late spring, 1906; the biennial plants of the Even-
ing Primroses are flowering, the annual specimens are
still very small. Tubes for spraying and sacks for arti-
ficial ])ollination . . . . . 323

102. A. The short-styled Evening Primrose, and B-F, its parent

form. b. A flower after the removal of part of its petals
and stamens, c. The same without petals, d. The
same without the tube and calyx, e. A flowerbud.
/. Ripe fruits. B-F. The corresponding parts of the
parent species, g. Styles, h. Longitudinal section of
ovary. /. Transversal section of base of style and calyx-
tube ......... 325

103. A biennial specimen of the Evening Primrose of Lamarck . 327

104. A. Spikes with almost ripe fruits of Oenothera gigas, a

mutant species. B. The same of Oenothera Lamarc-
kiana, its parent form ...... 329

105. A. A rosette of root-leaves of Lamarck's Evening Primrose

in September. B. A similar rosette of one of its mutants
(Oen. sciniillans) in the same age .... 330

106. The smooth-leaved variety of the Evening Primrose (Oeno-

thera laevijolia), a. A side-flower with ovate instead of
ob.cordate petals, one of the new, highly variable charac-
ters of the new form ....... 331

107. Oenothera muricata, a seaside plant which originated far

from the sea . . . . . . . . 337

108. Wulfenia carinthiaca, which grows almost only on the

Giirtnerkugel in Carinthia ...... 339

109. The smooth-leaved campion, a local plant of Bohemia with

a useless character .......

no. Two Alpine species of milfoil. A. The Achillea atrata of
calcareous soils. B. The A. moschata of siliciferous
soils .........

111. Palo Verde or Parkinsonia microphylla, a typical desert

plant from Tucson, Arizona ..... 346

112. Palo Christi or Koeberlinia speciosa, a typical desert plant

from Tucson, Arizona ...... 347

341
343

LIST OF ILLUSTRATIONS xiii

Fig. Pace.

113. A. Forest of giant Cacti (Cereus giganteus) near Tucson, in

Arizona. Opuntia in the foreground. Ocotillo, tree-
cactus, and Palo Verde in the middle .... 349

114. The desert botanical laboratory at Tucson, Arizona, with

two shrubs of Ocotillo {Fouquieria spletidens), giant cacti,
Opuntia, tree-cactus, and other shrubs . . -351

PLANT-BREEDING

COMMENTS ON THE EXPERIMENTS OF NILSSON AND BURBANK

CONTENTS

I. Evolution and Mutation ..... i

II. The Discovery of the Elementary Species of Agri-
cultural Plants by Hjalmar Nilsson.

A. Different Principles in the Breeding of Cereals . . 29

B. The Swedish Agricultural Experiment Station at Svalof 48

C. The Svalof Method of Producing Improved Races . 67

D. A Criticism of the Method of Continuous Selection . 90

III. On Corn-Breeding ....... 107

IV. The Production of Horticultural Novelties by

Luther Burbank.

A. Methods and Material i59

B. New Varieties in Fruits and Flowers . . .178

C. Hybridization and Selection ..... 202

D. Mutations in Horticulture . . . . .221

V. The Association of Characters in Plant-Breeding.

A. Association of Characters in Nature . . -237

B. Correlations in Agricultural Breeding . . -255

C. A Methodical Study of Correlations . . .271

D. Correlations in Fluctuating Variability . . . 289

E. Unit-Characters 309

VI. The Geographical Distribution of Plants . . 333
Index 353

EVOLUTION AND MUTATION

In the beginning of the last century Lamarck founded
the theory of a common descent for all Uving beings. It
afforded him the only possible means of explaining system-
atic affinity. He assumed that the influence of the en-
vironment was capable of changing the characters of the
organisms, and of fitting them for their life conditions. His
evidence, however, was very scanty and therefore he failed
in convincing his contemporaries.

Half a century afterward Darwin brought together such
an overwhelming mass of evidence that opposition had to
give in. His main point was one of comparative investiga-
tion. At his time it was universally assumed that species
had been created as such, but that subspecies and varieties
had been derived from them according to natural laws.
Darwin proved that no such distinction between species
and subspecies exists. Their marks are of the same nature,
and if a natural origin is assumed for one group, it must be
conceded for the other too. The same holds good for genera
and families, and even for the higher divisions of the system.

Moreover, Darwin showed that the sequence of the
appearance of organisms during geological times finds a
natural explanation on the assumption of the theory of de-
scent, and that the geographical distribution of animals and
plants is exactly as we should expect it to be if their common
origin were the main factor in assigning them their special
domains.

These broad proofs of the theory of evolution are quite
independent of the question by which means and in what
way new species are produced from the existing ones. This
question, however, appeals more directly to the imagination.

2 PLANT-BREEDING

and Darwin collected all the evidence concerning it which
he could find. The rapid victory gained by his views has
been due mainly to his discussion of this minor point.

Direct observations concerning the first appearance of
species in nature were not at hand. In agriculture and in
horticulture, however, numerous observations had been made,
and for a number of races and varieties the origin was his-
torically known. Distinct methods were in use to guide
these changes and to produce varieties which would comply
with the demands of practice. The grand principle of all
these methods was selection. Selection means guiding the
changes in the specific characters of organisms by cutting
off all those which are changing in undesirable ways, and
reserving for reproduction only those which differ advan-
tageously from the average.

Darwin proved that the origin of species in nature must
be the same phenomenon as the origin of races and varieties
in culture. He showed that in nature an analogous process
of selection is steadily active. More seeds are produced
and more cliildren are born than can possibly survive, and
the decision as to which are to H\'e and wliich must die de-
pends, on one side, on the life conditions and, on the other,
on the distinctive qualities of the competing indi\dduals. Of
course, in the single instances survival depends mainly on
chance, but in the long run the different chances may be
assumed to annul one another's influence, and the decision
falls to individual excellences and life conditions. In this
way the latter can be said to make a choice of the individuals
best fitted for the local conditions and this is what is now
universally known as the principle of natural selection.
It guides evolution, keeping it in the useful ways, and des-
troys all that try to diverge in opposite directions.

The theory of common descent is Darwin's theory, since
it has been founded by him on so broad a basis of facts as to

EVOLUTION AND MUTATION 3

insure almost universal acceptance. The theory of natural
selection is one of the means by wliich tliis position has been
reached. It is the apphcation of the breeding practice to
the phenomena of nature at large. Darwin's theory is
often designated as the theory of natural selection. This is
however, not the same as the theory of descent. The idea
of descent with modification, wliich now is the basis of all
evolutionary science, is quite independent of the question
as to how, in the single instances, the change of one species
into another has actually taken place. The theory of de-
scent remains unshaken even if our conception concerning
the mode of descent should prove to be in need of revision.
Such a revision has become necessary by the gradual
development of the study of variability. Darwin has demon-
strated that all the individuals of a given species differ from
one another to some extent, and that many of these differ-
ences increase or lessen their chances of survival. A struggle
for life ensues, and, sooner or later, the unfit individuals
succumb, thereby leaving the average of the species changed
to some sHght degree. Differences between isolated local
races afford the means of studying the efficiency of this process
of variability and selection. The question arises, however, as
to how far this variability may go under the influence of this
guidance. Is it Hmited or unhmited ? Can it proceed during
centuries and in the same direction, augmenting the differ-
ences to any extent, or is it bound by its original average
condition, without being able to diverge far from it? Can
it produce new characters and new quaUties or is it Hmited
to changes of degree in those that already exist? To all
these, and many other questions, an answer could not be
given at the time of Darwin, the evidence being too incom-
plete. It was necessary, however, to make a decision of
some. kind and thus it was universally assumed that the
changes by which species originate are slow, almost invisible,

4 PLANT-BREEDING

and may accumulate, in the lapse of time, to any degree.
All of the characters of living organisms were simply assumed
to be due to this slow process of gradual evolution guided
by natural selection.

Here, however, a first difficulty arose. We do not ob-
serve actual specific changes in nature. To meet this ob-
jection Darwin assumed the changes to be so slow as to be
invisible to us. Even the hfe time of a man would not be
sufficient to control them. By this supposition the evolution
of a flower or a seed or of highly differentiated organs (such
as the leaves of insectivorous plants) would require an enor-
mous time. From this a calculation could be made as to
the time required for the whole range of evolution of the
vegetable and animal kingdoms. The result was that many
thousands of millions of years were considered to be the
smallest amount that would account for the development
of hfe on earth from the very first beginning until the appear-
_ance of mankind.

Physicists and astronomers have objected to this con-
clusion. The objection has been brought forward from the
time when Darwin pubUshed his calculation. It has never
relented and has often threatened to impair the whole theory
of descent. The results of physical and astronomical cal-
culations concerning the age of life on this earth differ so
widely from the demands made by the theory of slow evolu-
tion as to be considered incompatible with them. The de-
ductions made by Lord Kelvin and others, from the central
heat of the earth, from the rate of the production of the cal-
careous deposits, from the increase of the amount of salt
in the water of the seas, and from various other sources,
indicate an age for the inhabitable surface of the earth of
between twenty and forty milHons of years only. This
large discrepancy has always been a weapon in the hands of
the opponents of the evolutionary idea, and there can be no

EVOLUTION AND MUTATION 5

doubt that it proves that the current view of extremely slow
and almost invisible changes must be abandoned.

Shortly after the publication of Darwin's Origin ofSpecies,
the Belgian anthropologist, Quetelet, submitted the variabil-
ity in measurement of the different parts of the human body
to a statistical investigation. He discovered that this kind
of variabihty follows distinct laws and that these laws agree,
in the main, with the law of probabiUty. Small divergences
from the average are numerous, larger discrepancies are
rare, and the rarer, the larger they are. Variabihty is thereby
limited, and is subject to a return to the average condition.
It may be moved from tliis average, to some extent, by a
change in the outward conditions or by a repeated selection
in one direction ; but, as soon as these causes and this selection
cease to work, a return to the average is unavoidable. Vari-
abihty may augment or diminish the quahties; it is linear,
consisting of changes along a simple hne, some being positive
and others being negative, but it does not strike into new
directions. It is no source of new r^uahties. The phenom-
ena which are controlled by this law and which are bound
to such narrow limits cannot be a basis for the explanation
of the origin of species. It governs cjuantitics and degrees
of cjuahties, but not the quahties themselves. Species,
however, are not, in the main, distinguished from their
alUes by c^uantities or by degrees — their very quahties may
differ.

From this discussion it may be seen that the slow and
gradual changes of ordinary variabihty and the production
of new characters are not of the same order. Variabihty,
in the ordinary sense of the word, is a broad conception.
It must be subdivided for the purpose of scientific investiga-
tion. The phenomena that follow Quetelet's law are now
considered as one group, which is called fluctuating variabihty
or fluctuation, since the individual quahties fluctuate around

6 PLANT-BREEDING

their average. The processes by which new qualities are
produced must be studied separately. Under the assump-
tion that these processes are neither slow nor invisible, but
consist in leaps and jumps such as are popularly indicated
by the name of sports, they are now called mutations, and
this great subdivision of the phenomena of variability is
designated, in consequence thereof, as mutability.

Darwin was well aware of the existence of different cases
of variability, and of the possibility of their bearing on the
theory of evolution. He considered the assumption of an
origin of species in nature by leaps and sports, such as were
observed to occur among horticultural plants. He pointed
out that the affinity of closely allied species can be explained
on this assumption as well as by slow changes. If we con-
sider all the varieties and subspecies of apples, or beets, or
of one of the cereals, and assume thousands of years for
their production, the changes may have been brought about
by rare sports as well as by long continued changes; the
effect, at the present time, would be the same. Darwin
agreed that this possibiUty could not be denied and that it
was a very weak point in his hypothesis of slow evolution.

The mutations must not be assumed to be considerable
changes. From a study of the differences among small
species, we may form some conclusion as to their probable
size. Common observation shows the difference between
allied species, ordinarily, to be quite striking; but a little
discussion and a closer inspection will easily prove that, in
such cases, the dift"erences are due to more than one, and
often to numerous, characters. In groups (such as bram-
bles, roses, buttercups, willows, and many others), where
large numbers of species are closely allied, the differences
between any two of them become smaller, and, the number
of distinct forms increasing, the distinction, in the end, may
become reduced to one single dift'erential mark for each two

Fig. I A. The Oa-k-leavedUazdnut (Coryhis Avellanalaciniata), a. natural
sport of the ordinary hazelnut (B),

8 PLANT-BREEDING

neighboring types. Such differences must be assumed to
be produced each by a single mutation. By tliis means
the significance of the mutations may best be judged, and
whenever species differ from their nearest alhes in a higher
degree, the inference is allowed that they have been origin-
ated by more than one mutation.

Since the publication of Darwin's theory, the probabil-
ity of such sudden changes playing an important part in the
evolution of species has always found some support. Of late,
the evidence has increased in this direction, especially under
the influence of Cope. Discontinuous evolution has been
defended among palaeontologists by Dollo, among zoolo-
gists by Bateson, and among botanists by Korshinsky. This
Russian author compiled the history of a large number of
varieties from the widely scattered horticultural literature
and showed that, in almost all cases where the history of
the origin of a variety was recorded, it originated suddenly.
Many other varieties, especially among trees and shrubs,
have been discovered as such in the field, and, although
their origin is not historically known, the constant absence
of intermediates pleads vigorously for the explanation of
tlieir differential qualities by mutation.

The conception of mutations agrees with the old view
of the constancy of species. This theory assumes that a
species has its birth, its lifetime, and its death, even as an
individual, and that throughout its life it remains one and
the same. Thus it is only natural that wild species are
almost always observed to be constant, since by a mutation
they do not change themselves but simply produce a new
type. This is alhed to its ancestor as a branch is to a tree,
the stem continuing its own growth, no matter how many
branches it produces. Just so a species may produce quite
a number of new forms without being changed itself, in the
the least, thereby. Among palaeontologists Scott has given

EVOLUTION AND MUTATION 9

forth this same view. According to his conception, species
are derived from one another by small shocks. Each
shock caused the old limits to be transgressed; but, after
it, the new species remained unchanged until, perhaps after
centuries, a new shock made it transgress its new limits.
Each single type (be it species, subspecies, or variety) is
thus wholly constant from its first appearance and until the
time it disappears, either after, or without, the production
of daughter species.

On the ground of the mutation theory, there is a struggle
for Hfe among species as well as among individuals. There
is selection, also, between competing species and among
the individuals of the same species; the fittest will survive, —
but this holds good for species as well as for individuals.
As to individuals, natural selection may, to some extent,
cause a divergence from the average type. But among
species, natural selection is the most potent factor, since it
eliminates some and thereby protects and favors others.
Thus we come to the conclusion that natural selection is
as active as Darwin assumed it to be, and is as pre-eminent
a factor in the process of evolution. It causes the survival
of the fittest; but it is not the survival of the fittest individ-
uals, but that of the fittest species, by which it guides the
development of the animal and vegetable kingdoms.

Summing up the main points of this discussion, we may
sketch the origin of species, according to the theory of mu-
tation, in the following manner. Species are derived from
other species by means of sudden small changes which, in
some instances, may be scarcely perceptible to the inexper-
ienced eye. From their first appearance they are uniform
and constant, when propagated by seed; they are not con-
nected with the parent species by intermediates and have
no period of slow development before they reach the full
display of their characters. They do not always arise, but

lo PLANT-BREEDING

only from time to time. A parent species may produce its
offspring separately at intervals, or in larger numbers during
distinct mutating periods. After this production, the old
species is still the same as it was before, and it subsists in
the midst of its cliildren. New forms are produced by the
old, either in one, or a few, or in numerous individuals; in
the latter case, the chance of survival is evidently enhanced.
Some young species will be better fitted for their life-
conditions than others, and the struggle for life will induce
a selection among them by which the fittest survive. Even
as the new species are produced locally and as the effect
of local causes, the struggle for life and natural selection
decide concerning the survival according to the local con-
ditions. These conditions thus have a twofold significance
for the development of the pedigree of the main groups of
plants and animals, but it is probable that they determine
the lines of progress chiefly by their selective activity.

The main arguments in the discussion of the production
of species by slow changes or by mutations were taken by
Darwin from the experience of agricultural and horticul-
tural breeders. Therefore it is desirable to inquire into
their real significance. Do they support the one or the
the other view? Darwin assumed that they gave proof of
slow changes, and took his arguments mainly from the agri-
cultural side. In horticulture, however, as we have seen
in discussing Korshinsky's work, the probability is on the
other side. In my experiments on mutability I have shown
that it is possible to repeat and control the origin of horti-
cultural and analogous varieties under strict experimental
precautions, and that the full proof may be given that they
originate at once, and not by a slow process of changes.
They may, in the first instance, appear with the full display
of their average character, or only with a small indication
of it as an extreme variant of its fluctuation, but in the latter

EVOLUTION AND MUTATION ii

case the average is often reached after one more genera-
tion.

I observed the origin of the pcloric toadflax and of a
double marigold, and produced, almost artificially, the twisted
variety of a Dracocephalum.

In the case of the toadflax, Linaria vulgaris peloria, the
change came suddenly, and more or less unsuspcctedly,
after a culture of about eight years. The ordinary form
produces, from time to time, some few five-spurred, regular
or peloric flowers. At once an individual arose which had
such flowers only. The next year the mutation was re-
peated. The seeds of the mutated individuals reproduced
the new variety almost exclusively, and each plant of it had
peloric flowers only. No intermediates were observed,
neither in the number of the spurs of the flower nor in the
number of the peloric flowers on the plants. It was as sud-
den a change as any horticultural sport, but its ancestry
had been purely fertilized and carefully recorded so as to
leave no doubt concerning the real nature of the mutation.

The double variety of the corn-marigold (Chrysan-
themum segetum) arose in my garden in a culture in wliich
I was increasing the number of the ray-florets by contin-
uous selection. During four years I had succeeded in in-
creasing this number to about sixty on each head, starting
from the cultivated variety, with an average of twenty-one.
All the ray-florets, however, belonged to the outer rows of
the heads, as in the original variety. At once a plant arose
which produced some few Hgulate florets in the midst of the
disc. This indicated the production of a double race.
When the seeds of this mutating individual were sown, the
next year, they yielded a uniformly double group; and from
this time the new variety remained constant.

The Dracocephalum moldavicum is an annual garden-
plant belonging to a genus in which Morren has described

^.

Fig. 2. A. The tOcLdf\a.x(Linaria vulgaris). B, C. Its peloric variety. D.
A peloric flower on an ordinary specimen.

12

13

14 PLANT-BREEDING

some beautifully twisted specimens. I succeeded in procur-
ing such a specimen in this species by cultivating a race of it
during some few years, selecting the specimens wliich
showed a marked tendency toward variation in the arrange-
ment of their leaves. The twisting appeared at once, but
the race has not been continued.

All these, and many other, experiments have been con-
ducted under conditions which allowed of a close scientilic
study. They confirm the common experience of the horti-
cultural breeder in stating the suddenness of the changes
and the immediate production of distinct races. They
show us the way in which analogous changes may have
occurred in nature, and make it probable that sudden changes
are, at least, an important factor in the evolution of the
vegetable kingdom.

With agricultural crops my experiments have been too
rare to give a definite result. The German breeders assumed,
as a rule, that they produced their races at will and by a
process of slow variability and repeated selection. It is
mainly upon this conviction that Darwin has based his con-
ception of an analogous slow improvement of species in
nature. This German method, however, has been sub-
mitted to a severe criticism by Dr. Nilsson, the director of
the Swedish agricultural experiment station at Svalof.
His pedigree-cultures have shown that the idea of a slow
accumulation of characters by repeated selection is due to
incorrect observations and to the use of untrustv/orthy
methods. According to his experiments, changes occur in
agricultural plants as suddenly as in horticultural species;
there is no essential difference between them in this respect.
By these discoveries the main support of the theory of slow
and gradual evolution is broken down, and the analogy
between artificial and natural production of species comes
to plead wholly for the theory of mutation. These new

i6 PLANT-BREEDING

facts will be dealt with in our next chapter, and it may be
sufficient, here, merely to have indicated them.

The principle of mutation is conducive to the assump-
tion of distinct units in the characters of plants and animals.
Even as chemistry has reached its present high develop
ment cliiefly through the assumption of atoms and mole-
cules as definite units, the qualities of which would be meas-
urable and could be expressed in figures, in the same way
systematic botany and the allied comparative studies are
in need of a basis for measurement and calculations. The
determination of the degree of affinity now largely depends
upon vague estimates and personal views; while, on the
basis of the theory of mutations, the relationship is meas-
ured by the number of the mutations which have made the
forms under consideration different from their common
ancestors. The mutations themselves have evidently oc-
curred in previous times and cannot be counted now. But
if it were possible to count their products, the characters,
the same aim could be reached.

The study of these unit-characters may be undertaken
in three different ways: first, by the production of hybrids;
secondly, by the investigation of associated characters; and
in the tliird place, by the direct observation of mutations
producing such units. In hybrids the characters of the par-
ents may be combined in different ways, but the unit-charac-
ters connot be spHt or divided. This follows directly from
their definition. Thus the different combinations may lead
to the distinction of the constituents of the mixture. In my
third chapter I shall deal with this question on the ground of
the experiments of Luther Burbank. They afford a suffi-
cient source of evidence to discuss this question and are well
deserving of a separate treatment. On the other hand, their
methods and scientific results are the same as those of the
European horticultural breeders, as described elsewhere.

Fig. 5. Lamarck's Evening Primrose {Oenothera Lamarck-
iana), a mutating species.

17

i8 PLANT-BREEDING

The association of characters is often called correlation.
It may be an accidental or a normal coincidence of charac-
ter-units. But more often the same simple character mani-
fests itself in different parts of the organism (as, for instance,
in the color of flowers, berries, seeds and foliage) and thereby
affords a means of investigating it. Of late, such associa-
tions have become of high importance, since selection may
be guided by them. Especially, in the isolation of new var-
ieties of cereals has this use proven very valuable. Our
fourth chapter will deal with these Ciuestions.

For the direct observation of the process of mutating, the
evening primrose of Lamarck affords, at present, an un-
equaled opportunity. It produces numerous mutants, and
does so in every generation, and almost any sample of pure
seed may be used for this study. This species was described
by Lamarck, from specimens of the l:)otanical garden at Paris,
a century ago. It seems to have since been lost. It was
re-introduced into European garden-culture, about the mid-
dle of the last century, by a nurseryman in London, who
received the seed, without name and in a mixed packet, cul-
tivated and multipKed it and sold it to the leading firms on
the continent. All the strains derived from this scource
show the same phenomena of mutability, as far as my experi-
ments go. Where the species is growing in America in the
wild condition, is not known, at present, and so it is impossible
to decide whether it has acc^uired the habit of mutating in
that condition or upon its introduction into European culture.

Twenty years ago, I found this species on a waste field
near Hilversum, in Holland, where it had escaped from culti-
vation and was rapidly multiplying itself. Here it had pro-
duced two new and distinct varieties which, up to the present
time, have not been collected or observed elsewhere. One
of them had smooth leaves, lacking the bubbles of the ordi-
nary form; it was a fine type with narrower leaves and petals,

Fig, 6. Leaves of Lamarck's Evening Primrose (A), and of two of its
mutants. B. Ocn. lata. C. Oen. scintillans.

19

20 PLANT-BREEDING

the latter often becoming ovate instead of cordate. The
other had very short styles, the stigma reaching only to the
mouth of the flower-tube, instead of being Ufted up above
the anthers. Its ovary is only partly inferior, and it ripens
only very few seeds in its capsules, which remain small. It
has, moreover, some associated characters in its fohage by
which it may be recognized before the flowering-period. In
my cultures, both these varieties were found to be constant
and pure from seed. Some further mutations have been
produced on the same field, but since they were also produced
in my experiment-garden, I shall not here mention them
separately.

In the year 1886, I collected some seed from the normal
plants of this field and sowed them in my garden the next
spring. This culture at once gave a new mutation wholly
unobserved until that time. Three individuals diverged
from the average, and all three in the same way. They con-
stituted a new type which has been called QEnothera lata or
the broad-leaved evening primrose. Its leaves have rounded
tips, its stems are weak and bending and scarcely reach half
the size of those of Lamarck's primrose. It has thick flower-
buds and produces flowers the petals of which often cannot
completely flatten themselves. The anthers are barren of
pollen, dry and twisted. Its ovary, however, is normal and
can easily be fertiKzcd by the pollen of the parent species.
In doing so the next generation is, of course, of hybrid origin,
but it does not produce intermediates but consists of some
typical CEnothera lata and some normal CEnothera Lamarck-
iana. By repeating the cross the lata type maybe kept indefi-
nitely, occurring in about the same numerical proportion
in each generation.

Starting from these mutations, I began a regular scientific
pedigree culture of Lamarck's evening primrose, fertilizing
the flowers artificially v/ith their own pollen, protecting them

Fig. 7. Mutants of the Evening Primrose. A. The
red-veined form (O. riibrinervis), which is of the same
size as the original species. B and C. The dwarfish
variety {Oen. nanella).

21

22 PLANT-BREEDING

from the visits of insects by paper bags and sowing, each
year, the seeds of some few normal individuals of the race
This pedigree embraces, now, about a dozen generations,
the first few of which were biennial, but the later annual.
From tliis stock of normal plants it has regularly repeated its
first mutation, producing some latas in almost every genera-
tion. The number of these mutants was, on the average,
about i^ per cent, the mutants themselves being always alike.

Moreover, my pedigree culture has produced quite a
number of other mutants. The most frequent among them
is a dwarfish variety, the first flowers of which open when the
stem is only some few inches high. It is called Oenothera
nanella and occurs as frequently as the (Enothera lata. It
is completely fertile and produces an abundance of seeds, all
of wliich give the same dwarf type, without (>ver reverting to
the high stature of the parent species. I have cultivated
these dwarfs during five, and more, generations and have
found them true to their type.

The first generations of my pedigree culture had to meet
with all the difficulties of a new experiment with unknown
and partly unsuspected results. Accordingly, they yielded
only a small number of mutants. As soon as the method had
been elaborated, this number rapidly increased. In the
spring of 1895 I sowed seed enough to have about 14,000
young seedling plants, which I cultivated until they clearly
showed whether they would mutate or not. The mutating
individuals were than isolated and grown under very favor-
able conditions, but of the normal plants the larger part were
destroyed. All in all, I isolated 60 dwarfs and 73 lata and
five wholly different new types. Two of them were rare, one
having been found only in one (O. gigas)and the other in two
individuals (O. leptocarpa). Two others were less rare, the
rubrinervis appearing in eight, and the albida in fifteen speci-
mens. The fifth was the most frequent of them all, spring

1

-. ■■ . -rv^v-'^^

mM.

.^.

**

"^

dP^^kEi '

jK^^^^iyBj

^P

Fig. 8. A flowerspike of the giant mutant {Oenothera gigas), which origi-
nated in my garden, 1896.

23

24 PLANT-BREEDING

ing from the main stem of the Lamarckiana in 176 of the
14,000 seedhngs. It was called oblonga. All these forms
were purely self- fertilized and yielded uniform races without
reversion to the original evening primrose of Lamarck.

With the exception of the gigas, which has not been re-
peated in this pedigree, all the types spring more or less regu-
larly, in every generation, from the pure parent stock. As
often as they were purely fcrtiHzcd they produced constant
strains, which, however, did not differ from the previous races
of the same name.

Besides these, quite a number of minor mutations have
occurred in my cultures. Some of them died in early youth or
before flowering ; others were barren of pollen, or not capable
of fertilization, and yielded no seeds. Some were too weak
for the conditions of my garden and succumbed, sooner or
later, mostly during the winter after their germination. The
range of mutability of this primrose, evidently, has not been
exhausted; and even during last summer a wholly new type
made its appearance.

A main point in these observations is that the mutations
occur suddenly, without preparation and without interme-
diates. Nothing indicates on the normal plants what their
seeds will produce, and there is even no means at all by which
to decide beforehand whether the fruit of one individual, or
one branch, will be richer than any other in the production
of mutations or of some distinct mutant. The distribution
of mutating seeds seems to depend simply upon chance. Nor
are there intermediates. Each mutant is as good a repre-
sentative of its type as its progeny will be; it does not need
any special cultivation or improvement to reach the full dis-
play of its character. No half-mutants are seen, neither
from seed of the parent form nor from seed of the first mu-
tant itself. These sharp distinctions clearly indicate that
each mutation consists of the production of a single unit-

Fig. 9. A flowerspike of the red-veined mutant {Oenothera rubrinervis),
which has been produced almost yearly by the parent species.

25

20 PLANT-BREEDING

character; because, if the characters were compound, they
would spHt, from time to time, and be divided into their con-
stituents. By this means a method is given of studying the
expressions which the same unit-character may assume in the
different organs of a plant. But this point will be more
closely studied in another chapter.

The question now arises, whether it must be supposed
that species in nature ordinarily originate in the same way
as in the case of the evening primroses. Of course, the de-
tails of the process will be different in different cases. The
number of the new types and the frequency of the mutating
individuals in each will differ; sometimes they may, perhaps,
be more rare and, in other instances, more crowded. Other
differences there will be, also. The main point is, however,
that mutations occur suddenly and by leaps. One genera-
tion is sufficient to produce the whole new type. This is a
manifest contrast with the prevailing conception of slow and
almost invisible changes producing new species. It may
shorten the geological time rec|uired for the evolution of
the whole living world and bring it within the limits derived
from physical and astronomical evidence. Thus the theory
of mutation satisfies these demands.

The cases observed in horticulture, the constancy of wild
species, the behavior of characters in crosses, the occurrence
of sharply defined small species within the ordinary species
of wild plants and even of agricultural crops, and many other
groups of facts, lead to the same conclusion. On the other
hand, the slow change of one species into another has not, as
yet, been proven in any distinct and clear case. Therefore,
we may assume that the mass of the present evidence points
to the conclusion that species originate laterally from other
species, by sudden leaps. These leaps we call mutations.

Fig. lo Dr. Hjalmar Nilsson, Director of the Swedish Agricultural Ex-
periment Station at Svalof.

28

II.

THE DISCOVERY OF THE ELEMENTARY

SPECIES OF AGRICULTURAL PLANTS

BY HJALMAR NILSSON.

A. DIFFERENT PRINCIPLES IN THE BREEDING OF

CEREALS.

From the beginning of civilization, the cereals have taken
a prominent place in human culture. No industry has been
so intimately connected with the interests of mankind, and
upon no other agricultural crop has progress been so largely
dependent. Long before the time of the ancient Egyptian
kings, of the Romans and of the lake-dwellings of central
Europe, the cereals yielded the principal nourishment in all
the countries of the world where civilization developed itself.
Solms-Laubach has pointed out that China and Egypt have
cultivated mainly the same species and sub-species of grains,
and that on this ground it must be conceded that their cul-
tures have had a common starting-point. Three or four
thousand years before Christ, the principal varieties must
have been known to mankind, and it may even be assumed
that the very first beginning of this culture is much older.
Its probable origin is the central part of Asia, since only this
region can have been its common source for the Chinese and
Egyptians.

Having so deep a significance, the cereals must have been
given more attention and more care than any other crop.
According to some verses of Virgil, the Romans knew their
cultivated races to be far from pure and uniform. They
also knew that care had to be taken in the harvesting of the
grains destined for sowing, since otherwise the races would
surely deteriorate. Each year the best ears had to be selected
in order to keep the varieties pure from an overwhelming

29

3°

PLANT-BREEDING

Fig. II. Poland wheat
{Triticum polaniciim).

increase of the unavoidable admix-
tures of little worth.

During the middle ages no records
seem to have been made as to the
methods of cultivating cereals. Wheat
and barley had been the grains of the
ancients; to these, oats have been
added during the period of the lake-
dwellings, and rye is the most recent
of the European species, having been
introduced into Europe during the
middle ages. Corn, of course, is of
American origin, and has been con-
nected with the development of the
ancient American cultures, quite in
the same way as the grains were con-
nected with those of the old world.

The idea of improving these valu-
able crops seems to have presented
itself only after the beginning of the
last century. Different principles
were set forth, as soon as the possi-
bilit}' of improvement had once been
ascertained. Some of them were of
a more practical nature, resting on
direct observation, but others relied
on theoretical views concerninsr the
influence of environment on the qual-
ities of living organisms. Both of
these main directions have attained a
high degree of significance in agri-
cultural practice as well as in the
purely scientific discussions concern-
ing the origin of species in nature.

NILSSON'S DISCOVERY 31

English breeders have, as a rule, preferred the more practical
line of working, but their results have been isolated, and have
not been combined into a definite svstem. German breeders,
on the other hand, have followed the theoretical principle
of slow amelioration, and have developed this idea into a
broad system, which has been applied by several of their most
prominent men to the improvement of numerous varieties.

Darwin, as is generally known, chose the principle of
slow and gradual changes as affording the most reliable
facts for his discussion of the manner in which species are
produced in nature. In doing so, he has brought the Ger-
man method to the rank of a scientific principle and secured
for it the interest of the students of biology at large, but has
almost thrown into obhvion the other side of the question.

Of late, however, new facts have been discovered, wliich
are of a nature to change the whole aspect of this part of
the science of evolution. At the Agricultural Experiment
Station of Sweden, at Svalof, the German method has been
extensively tested, and the result has not been favorable to
it. New discoveries have been made which go to prove that
the whole principle of gradual changes rests on an insufficient
knowledge of the laws of variability of agricultural plants,
and may be replaced by more simple and more direct methods
as soon as these laws are exactly studied. It is my object to
give a survey of the deep significance of these Svalof experi-
ments, partly in their practical bearing on agricultural plant
breeding, but mainly in their complete compHance with the
doctrine of elementary species, and in their appreciation of
these as the true material from which selection has to make
its choice. I shall endeavor to point out that these new dis-
coveries must deprive the principle of gradual ameliorations
of its present high rank in agricultural practice, as well as
of its significance as a support for the prevailing views con-
cerning the origin of species in nature.

32

PLANT-BREEDING

Before doing so, however, an historical sketch of the
principal methods and achievements of the most renov^ned
breeders of cereals may be given. It will facilitate our

Fig. 12. A. Bellevue de Talavera-wheat, isolated by Le Couteur. B.
Bearded white wheat, produced by Patrick Shirreff. C. Squarehead
wheat, the most famous production of the same breeder.

appreciation of the most essential features of the wonder-
ful variability of these plants, and will prepare us for an
unprejudiced judgment of the opposite views concerning the

NILSSON'S DISCOVERY ^^

significance of different kinds of variations for breeding
experiments and for scientific discussions.

The first to discover tlie principle of improving cereals
by selection was the English breeder, Le Couteur. He lived
in the first part of the last century on Jersey, one of the
islands in the Channel, off the coast of France. Once he
was visited by Professor La Gasca of the University of
Madrid, who, far from admiring the purity and uniforiTiity
of liis host's cultures, pointed out to him how, in reahty,
they consisted of a mixture of more or less easily recognizable
types. He suggested the idea that these types might have a
different share in the harvest of the whole field, some of
them being probably more and others less productive than
the average. In a field of wheat, he succeeded in distin-
guisbiing 23 forms, and in other cultures similar indica-
tions of variabihty were observed. After his departure, Le
Couteur saved the ears of the indicated types separately,
and sowed their grains in small field plots in order to com-
pare their productivity. He does not seem to have had any
theoretical view concerning the causes or the nature of the
observed dift'erenccs, but simply assumed that the progeny
of his selected plants would be Hke the parents. On this
point he soon found liimsclf justified by the results of his
experiments. He had produced a group of new types of
which some proved better and others less valuable than the
ordinary sorts of liis fields. The best new varieties, isolated
in tliis way, he then multiphed, and afterwards put them
upon the market. One of them is still grown in England
and the northern parts of France on a tolerably large scale.
It is a kind of wheat called "Bellevue de Talavera" and it
is known to be a very pure and uniform type. It is so
uniform that it does not afford any deviations by which it
can be subjected to further selection, and all trials in this
direction have been in vain. Many breeders of later times

34 PLANT-BREEDING

have approached this high degree of invariability in the pro-
ducts of Le Couteur's selection, and only at present is it
recognized as an instance of one of the most common laws,
wliich rule the phenomena involved.

Another celebrated breeder who worked on the same
principle, though after a somewhat different method, was
the Scottish agriculturist, Patrick Sliirreff. He lived in
about the middle of the nineteenth century and had Ms
farm at Haddington in Haddingtonshire, During the first
period of his work, he had no better conception concerning
the purity of his fields than his contemporaries. But he
observed that, from time to tim.e, and as he thought by mere
accident, a pl^nt occurred which seemed far more promis-
ing than all the remainder of the same field. Such individ-
uals he marked, helping their development by pulling out
their neighbors if they were crowded and surrounded them
by all manner of attention. Then he saved their seeds
separately and sowed them, in order to multiply his new
types as fast as possible. That such isolated individuals
would yield a uniform progeny and become the ancestors of
constant races he took for granted, and it is very curious to
note in his writings that he did not judge it worth while to
discuss this point, or to state the fact as he observed it.
His races w^re pure, and there was no single reason for him
to suggest that it could have been otherwise.

Shirreff's exceptional plants were very rare, so rare even
that in the first period of nearly forty years, he succeeded
in isolating only four new varieties of prominent value.
His first discovery was made in the year 1819. He observed
a plant of wheat which surpassed its neighbors by its high
degree of branching. It yielded 63 ears with about 2500
kernels. He saved the seeds, sowed them on a separate
field and at considerable distances apart so as to induce in
all the plants the same rich branching. He contrived to

NILSSON'S DISCOVERY 35

multiply it so rapidly that it took only two generations to get
seed enough to bring it advantageously into the trade. He
gave it the name of Mungoswell's wheat, and it soon be-
came one of the most profitable varieties of Scotland. It
has found its way into England and into France, where it
is still considered one of the best sorts of wheat.

It is interesting to note that Shirreff had no idea of the
necessity or even of the usefulness of a repeated selection.
On tliis point he wholly agreed with Le Couteur. Without
exercising any choice, he sowed all the grains of his selected
plants and of their progeny, his only aim being to multiply
the new form as quickly as possible. They yielded a uni-
form race, and were simply expected to do so.

Only five years after his first selection, another excep-
tional plant caught his eye. It was an exceedingly tall
individual in one of his fields of oats. He saved and sowed
its seeds separately as in the previous case and won a variety
which has since been largely cultivated under the name of
Hopetown oats. His remaining varieties w'cre the Hope-
town wheat, found in 1832^ which was discovered and
multiphcd in c[uite the same way, and the Shirreff oats,
concerning the origin and treatment of which he has not
judged it worth while to give any indications. Both of
them have gained a high reputation and a widespread
culture in Scotland as well as in some other European
countries.

Until the year 1856, these four varieties were his only im-
provements. At that time, however, he had acquired more
experience concerning the variabihty of his cereals, and he
resolved to profit thereby. He had observed that though
exceptionally promising plants arc of course very rare, less
promising individuals may be met with in larger numbers.
They would not yield such excellent races as the four men-
tioned above, but notwithstanding that, they might sufh-

36 PLANT-BREEDING

ciently surpass the average to be advantageously selected
and cultivated. The trials would have to be made on a
larger scale, and the results would be less striking, but on
the other hand, improvements could be brought about in a
far lesser number of years. Or, to state it more correctly,
the results w^ould no longer be dependent on rare and casual
discoveries, but would be brought about systematically.

He began his selections, after this new method, with
wheat, and saved 70 ears from different individuals. All
of them seemed to promise more than the average varieties
of his fields. Of course the kernels were sown separately
for each mother plant, and their progeny was accurately
tested and compared. As previously, he took it for granted
that all of these new strains would be constant and uniform;
he observed the fact but did not judge it interesting enough
to mention it specially. Among his 70 strains he chose at
the end the three best ones, multiphed them as fast as pos-
sible in order to bring them into the trade, and rejected all
the others. Those three received the names of Shirreff's
Bearded Red Wheat, Shirreff's Bearded White W^heat, and
Pringle's Wheat. For many years they have had a notable
place among the best local varieties, and the white variety
among them has even found its way into England and
France.

Having obtained these results with wheat, he started,
in the year of 1862, a similar experiment with oats. Four
of Ms selections proved to excel the common sorts and were
introduced into the trade. They bear the names of Early
Fellow, Fine Fellow^ Long Fellow, and Early Angus. Like
the wheats, they have been constant and uniform from the
very beginning.

Ten years afterward, Shirreff published an account of
his results and of his methods. It was a little book, printed
only for private distribution. But it has been translated

NILSSON'S DISCOVERY 37

into German by Dr. Hesse for the use of the general public.
It is largely devoted to the description of the superior qual-
ities of his varieties, and the historical evidence concerning
their origin is only incidentally given. From his statements,
we may gather that at first he assumed his mother plants
to be sports, but afterwards took them to be simply old con-
stituents of the ordinary cultivated varieties. He observed
these to be mixtures, consisting of more and of less abun-
dantly yielding types, and on tliis observation founded the
method which he followed during the latter part of his life.
He satisfied himself that even within these mixtures the
constituents were uniform and constant races, and there-
fore it was only natural that after isolation they would re-
main so. Shirreff seems not to have had any idea of the
possibility of the existence of another form of variability
as a starting point for further improvement. Considering
the great importance which has been conceded in Germany
to this possibility, even during the latter part of Sliirreff's
life, it is not without interest to lay some stress on this fact.
The more so, since he had in mind the desirability of other
ways to reach the same purpose more surely and more
quickly. He turned himself to hybridizations and made
some valuable experiments on the crossing of cereals, and
from his statements it seems quite evident that he did so
only in the firm conviction of having exhausted the possibili-
ties offered him by variability alone.

Le Couteur and Patrick Shirreff seem to be the only
breeders of cereals who have worked on the principle of one
single initial selection and of subsequent rapid multiplica-
tion without renewal of the choice and without isolating the
best individuals during the following generations. On this
point they are to be considered the precursors of the method
which has of late been discovered anew, at Svalof. But
they had only a very limited appreciation of the importance

^8 PLANT-BREEDING

and productiveness of the principle involved in their method
of selection.

At nearly the same time with the latter experiments of
Shirreff, another renowned breeder began to improve cereals
by selection. At Brighton, in one of the southern districts
of England, F. F. Hallett began his work in the year 1857.
He seems to have known the improved varieties of Le Couteur
but not those of Shirreff. He started from quite another
point of view, which did not rest upon the observation of
the variability of his grains, but was derived from his previ-
ous experience in the breeding of cattle, especially in that of
the short- horns.

His principle was that each plant has one head which is
the best of all its ears, and that in the same wav each ear
has one best kernel. Moreover, he was convinced that the
best kernel of the whole plant is always to be found in the
best ear. He also assumes that the qualities of the single
kernels are inherited by the plants which they produce.
From these premises he concluded that varieties could be
improved by choosing the best kernel of the best ear for
their reproduction. This choice had to be repeated through
a series of generations, but his experience taught him that
though the gain was large in the beginning, it did not con-
tinue so, but soon reached a limit which it was practically
impossible to transgress.

Two other features distinguished his work from that of
Le Couteur and Shirreff. In the first place, he tried to
improve his plants directly. He satisfied himself that a
plant, in order to attain its utmost development, must have
ample food at all seasons, and that for this purpose not only
manure but also depth of soil and space were essential.
Therefore he planted Ms selected plants in a httle garden
near his house, gave them the best garden soil and the
ordinary culture and treatment of garden plants. By this

Fig. 13. A. Hallctt's pedigree Chevalier barley. B. Hal-
Ictt's pedigree wheat.

39

40

PLANT-BREEDING

means he increased the number of their culms and heads
and the number of the spikelcts and kernels in the individual
ears. Twenty to fifty and more ears on a plant of wheat

HALLTTT'S
NURSERY (PEDIGREE) WHEAT,

Bred" upon the same principle of REPEATED ScIccUon which has produced our pure

races of Animals.

t i

s

ONE OF THE
ORiaiNAL TWO EARS.

REPEATED

11

9 ■?

II

2

la lai

Hi

-^■-^—=4:

up. REPEATED -m.m , ;M^

Tha Bar containing 12T Or^iln^ BEST EAR, 1861 Now eiartlng potct, 1861.

--^'■<-

HOW OUR WHEAT CROPS MAY BE DOOBUE3).

Fig. 14. A reproduction of part of the first advertisement of pedigree
wheat by F. F. Hallett. See the Titnes, London, June 18, Nov. 8, and Dec.
19, 1862.

became the rule, and ears with less than 80-100 kernels
were commonly rejected. This large increase can in some
sense be called artificial. It appears as a direct result of
the change of culture and therefore came wholly or almost
wholly during the very first year of the selection experiment.

NILSSON'S DISCOVERY 41

Of course the influence of better nourishment can only
attain its highest degree in the lapse of some generations,
since only the very best nourished kernels will yield the
very richest plants. In some cases, this process of artificial
amelioration will be rapid, but in others more or less slow.
Some instances may be given, Hallctt's "Original Red
Wheat" was started from an ear containing 47 kernels.
The next generation yielded an ear of 79 grains, and the
second came up to 90 in the richest ear. During the seven-
teen following generations, this Umit has practically not been
exceeded, the richest ear during all that time having produced
only 91 kernels. In other cases the development was equal-
ly rapid in the beginning, but lasted during a longer period.
The Hunter's Wheat began with 60, increased in the first
year to 90, and then during some twelve years came up to
106 in the best ear. The Victoria Wheat began with 53
and slowly increased to loi, the gain of the first generation
being only seven kernels for the best ear. Hallett assumed
that by this treatment the hereditary qualities were affected
in the same way as the visible characteristics, or in other
words, that the varieties were directly improved by the cul-
ture, the selection having only the purpose of fixing the
acquired qualities.

A second feature of Hallett 's method was the great care
bestowed by him on the comparison and testing of his plants.
For each single individual, the heads were counted and the
exact number of kernels in each ear traced. These figures
were considered as the main qualities according to which
the plants were judged, and on this ground the average
specimens and those of minor worth could be eliminated.
The prominent ones were then brought to his study and
minutely compared in all their visible marks. In this way
the very best specimen was isolated, and the same work
begun for its culms and ears. Only one ear was ultimately

42 PLANT-BREEDING

chosen for the sowing of the next generation, and this was
the best on account of its having not only the largest number
of kernels, but also the biggest and best formed ones of them
all. Repeatedly HaUett has insisted upon the immense
amount of work which this kind of selection yearly required.
This is the more curious since at the present time hardly
anybody attributes much importance to a choice of the best
seeds on a given individual, provided only that small or un-
healthy kernels are sufhciently excluded.

For Hallctt, on the contrary, the choice of the one best
kernel on the whole plant was the real aim in his selection.
He tried all means for comparing the individual kernels of
his one superior ear with one another and for Imding out
the best one. He made investigations embracing, on one
side, their visible marks, and on the other their places on the
ear, those in the middle part being in the main the better
ones. But he could not discover chstinct laws and so had
to give up the whole system. Leaving aside all comparison
of the kernels of his chosen head, he resolved to sow them
all and to delay their study until the next generation. In
this he repeated his testing in the manner described and
judging the kernels from the plants they had produced, he
was enabled to discern among them the one by means of
which he wished to continue his race.

To this method of selecting each year the best kernel on
the best ear of the best plant, Hallett has given the name
of pedigree-culture. Its essential feature is the repeated
selection. Some of his varieties were given to the trade
under the names of pedigree wheats and pedigree oats. Of
the latter, his "pedigree white Canadian oats" and his
"pedigree black Tartarian oats" may here be mentioned.
Both were introduced in the year 1862. He claimed that
his gradual amelioration gave better varieties than the princi-
ple of the isolation of single plants. Tliis may be seen by

NILSSON'S DISCOVERY 43

the title of the address deHvered by him in London in 1862,
in whicli he first pubHshcd liis results and his views. It
was entitled, "On pedigree in wheat as a means of increas-
ing crop." The improvement was obtained by the increase of
the size of the ears, their number of kernels and the size of
the latter. The number of heads on a plant he did not con-
sider as a subject of selection, but rather assumed that it was
wholly determined by the relative distance between the plants
and therefore by the space given them in sowing. For him,
the productiveness of a field was proportional to the yield
of the single ears.

Moreover, he assumed that his pedigree-races were not
only to be ameliorated but must be kept up to their highest
point of development by continued selection. As soon as
selection ceased, they would return to their original starting
point and their superiority over the ordinary cultivated
varieties would disappear. This assertion has a distinct
and deep significance in agricultural practice, and has
gained a great deal of influence in the discussion of theoret-
ical questions as well. For practice it means that all the
seed destined for sowing should be produced directly from
the pedigree-stock, and that this is to be kept constantly
under the same conditions of treatment and sharp selection.
The truth of this assertion has been accepted by his custo-
mers, and this fact has left the production of seed grain
almost entirely in his hands. It is easy to see that the gain
made by the breeder of a new variety depends, for a large
part, on the acceptance of this proposition. In the varieties
produced by Lc Couteur and Shirreff, all seed is of equal
value, provided the races are kept pure and free from admix-
ture. Any" one may multiply them with the same success
as the original breeder, but on Hallett's principle all the
profit of the production of reUable seed grain was given into
the hands of him who kept the original pedigree.

44 PLANT-BREEDING

I need not now discuss the truth of this assertion, since
the same principle has been accepted by the German breeders.
I might, however, point out that the real difference between
Hallett's method and that of his two previously mentioned
countrymen is to be sought in the choice of the starting points
of their experiments.

Le Couteur and Shirreff have expressed themselves
clearly on this point. With them, all depends upon the
first choice. What remains to be done afterward, is only
the multipHcation of the progeny of the chosen plant.
Hallett, on the other hand, is silent on this most essential
question. Like them, he started, in each single case, from
one plant, and therefore must have made a choice among
the types which his fields afforded him. On Shirreff 's
conception, this choice must have been the decisive point in
Hallett's work, and not the subsequent selection, and that
this is true may be proven by his arguments. In the first
place, Hallett has brought into the trade new and distinct
varieties, and not merely more productive strains of the ordi-
nary sorts. This may be seen by the names of the forms
already cited, and to which the very distinctive types of his
Golden Drop wheat and Chevalier barley may be added.
Moreover, it is proven by the fact that his varieties have
kept their place in agriculture at large and are still keep-
ing it, although it is a long time since Hallett himself dis-
continued their pedigree-culture. They are now known
to be independent varieties Hke those of Le Couteur and
Shirreff.

A second argument is given in the fact that the value of
Hallett's varieties is dependent on his first choice, and that
if this should prove a mistake, no subsequent selection is
adequate to amend it. The proof of this is given by the
miscarrying of some of his pedigree-cultures. Of course,
most of these cases he will hardly have mentioned, but it is

NILSSON'S DISCOVERY 45

a well-known fact that his "Original Red Wheat" after-
ward proved to be a failure.

A very remarkable principle has been introduced of late
into the methods of improving cereals by two highly distin-
guished breeders. Working independently of one another,
they have come to the same idea, and the amehorations they
have brought about give proof of the correctnessof their views.
At the agricultural experiment station of Minnesota, W. M.
Hays has applied it to the improvement of wheat, and in
Germany on his farm at Petkus von Lochow has appUed it
to the selection of rye. The idea is the judging of the hered-
itary value of a plant, not by its own visible marks, but by
the average value of its progeny. It must be granted
that the visible qualities of a plant are only a very imper-
fect basis of measurement of its fitness to reproduce these
quahties in its progeny. The direct study of tliis progeny
in itself must be a far more reliable guide in such an
estimate.

The new principle was of course combined with the
choice of single parent plants as the starting points for new
races, and in this important feature it complies with the
principles laid down by the two first English breeders whose
methods I have discussed. But with them the first choice
was the principal act, although Le Couteur as well as Shirreff
in his second method have largely relied on the comparison
of the progeny of their first selections and rejected all those
that proved inferior to his expectations.

In Minnesota, the most widely cultivated varieties of
wheat were Fife and Blue Stem, and both were decidedly
inferior to the ordinary spring wheat varieties of other states.
However, they showed themselves to be as impure as any
other ordinary sorts, and thereby yielded material for method-
ical improvement. Hays chose from among them a con-
siderable number of types, and after sowing the seed of these

46 PLANT-BREEDING

single mother plants, he compared their yielding capacity
in the next generation. In order to have an easy standard
of comparison, he sowed a hundred kernels of each and
thence derived the name "centgener pov/er" for the index
of productiveness of the single races isolated in this way.
He claims to have obtained varieties which, under the same
culture and treatment, will yield lo to 15 per cent more than
the old unpurified wheats of Minnesota.

The same principle of judging the parent plant by the
average value of its progeny, and of founding selection on
this mark, has been applied by von Lochow to rye, and it is
said that liis new race of "Rye of Petkus" as it is called,
excels all the older improved German kinds of rye, and that
even the celebrated rye of Schlanstedt may soon prove to be
surpj.ssed by it.

We have given a survey of the most prominent and most
renowned principles in the breeding of cereals, and have
only to complete our list by a description of the method
followed by the larger number of the breeders of Germany.
Among them, Heine, Drechsler, Mokry and Rimpau may
here be named. Their purpose was to improve the ordinary
varieties by continuous selection, directed according to
distinct \dews and requirements. They considered the
starting points of the English breeders as accidental sports
which no doubt might be made use of with advantage, but
would only yield improvements of an inferior rank.

Two features are essential to this German method.
First the initial choice, and secondly the slow and gradual
improvement by selection. In this first choice they did not
try to obtain deviating types and to isolate them from
among the throng. Quite on the contrary, they selected the
best representatives of the variety they wished to improve, in
order to be sure to retain all of its good features in the new
race and to combine them with the new characters which

NILSSON'S DISCOVERY 47

they thought it possible to give them. Starting from this
point of view, it was essential not to begin with one single
mother plant, for this might perhaps possess, among those
quahties which necessarily or at least ordinarily escape obser-
vation, some inferior ones, which, it must be feared, might
destroy the whole effect of the amehorations obtained on
other points. Dependence on soil and manure, resistance
to disease and other essential quahties are not so easily taken
into consideration when the selection is performed only at the
time of the harvest, as was then the custom. In order to
become as independent of these as possible, the only way
seemed to start with c^uite a considerable number of indi-
viduals and to rely on the laws of chance, trusting that these
would keep all quahties in their average state, except those
which should be consciously subjected to selection. It
was this group of individuals that was to be ameliorated.
A scheme of the desired improvements was made, and each
year those ears or panicles wxre selected which more fully
comphed with it than the remainder. The result was a
slow progress, but it was thought to be more rehable than the
sudden amelioration of the Enghsh breeders. Moreover,
sudden improvements are, as a matter of fact, hmited in
their degree, and even the pedigree-cultures of Hahett did
not escape from this objection. The German principle
was assumed to be unlimited, progress along the prescribed
hnes seeming to be always possible.

As pointed out in the beginning, Darwin has, in large
part, founded his theory of the slow and gradual change
by which the species of plants and animals are transformed
into one another, on the views of the German breeders of
his time. For this reason we shall have to subject their
principles to an elaborate criticism and the short indication
given may therefore be sufficient for our present purpose.

The most general conclusion to which our liistorical

48 PLANT-BREEDING

sketch has led us is obviously that by very different methods
and under the influence of widely divergent theoretical
premises, equally good improvements have been obtained.
We may add that even in the number of new and useful
varieties produced, no single one among these methods evi-
dently excels the others. It is always a small number, not
exceeding ten or perhaps twenty novelties in each single
instance, and ordinarily even far less. Thus all these princi-
ples are seen to have only a limited application, and perhaps
failures have been more numerous than successes although
as a rule only the latter have been recorded. Hence we may
conclude that our knowledge of the variabiUty of cereals
is not yet sufiEicient to enable us to exhaust all of its possibili-
ties, or at least that such a knowledge was not in the posses-
sion of the breeders whose great achievements have given
the material for our present sketch.

B. THE SWEDISH AGRICULTURAL EXPERIMENT STATION

AT SVALOF.

During the last twenty years, experiments in the breed-
ing of cereals and other agricultural crops have been con-
ducted on an unusually large scale at the Swedish experiment
station of Svalof. Considered from a practical point of view,
they have produced quite an astonishing number of new
races, by which agriculture in almiost all the districts of
Sweden has been greatly improved, and which are now at-
tracting the attention of numerous agriculturists in other
countries. Their methods took their origin from those fol-
lowed in Germany, but were soon changed, and may, at
present, be more closely compared with the work of Le Cou-
tcur and Shirreff, though developed quite independently
of these men, whose ideas were, at that time, only locally
appreciated.

For the students of the problems of evolution, the methods

49

50 PLANT-BREEDING

and the results of the Svalof station have a very deep signifi-
cance. They confirm the fact that the ordinary cultivated
varieties of cereals are by no means pure, but must be con-
sidered as mixtures of well defined types. Moreover, they
show that these types are far more numerous than was pre-
viously supposed, and include hundreds of forms within each
of the now prevailing sorts. They also show that the differ-
ences among these newly discovered elementary types are
far greater than might be suspected from the study of the
varieties isolated by other breeders. The range of variabil-
ity disclosed by these new studies is simply so wide that it
affords all the required material for almost all the selections
desirable at present, and will no doubt continue to be an
inexhaustible source of improvements for a long succession
of years. They are founded on the principle of single selec-
tions, and the range of application of this method is proven
to be so extensive as to make all ideas of repeated or con-
tinuous selection simply superfluous. It is even so rich in
its productiveness that there is scarcely any room left for
other methods of improvement; and especially should all
endeavors of winning ameliorated varieties of cereals by
means of hybridization simply be left out of consideration,
as compared with the immense number of more easily pro-
duced novelties which this method offers.

Leaving the teachings which may be derived from this
work in the study of the evolution of the organic world for
another chapter, I shall now try to give an idea of the work
itself. This may be divided into two parts; the first com-
prising the use and criticism of the German method, and
the second embracing the discovery and application of the
principle of selecting elementary species.

Some historical details may precede this discussion.
Svalof is a httle village in the Swedish province of Schonen,
situated in the neighborhood of Helsingborg, Lund and

NILSSON'S DISCOVERY 51

Malmo, close to the southwestern shore, and opposite Co-
penhagen in Denmark. In this village, a company for the
production and improvement of seed-grains for the southern
part of Sweden was organized in the year 1886. Its aim
was the procuring and testing of new and foreign varieties
of agricultural crops, in order to replace the Swedish sorts,
which at that time were slowly but manifestly deteriorating.
This deterioration was discovered to be a consequence of
the multiplication of admixtures of less value, wliich, though
rare and unobjectionable in the countries whence the vari-
eties were derived, were seen to thrive in a most obnoxious
way under the influence of the Swedish soil and climate,
and to lessen the value of the harvest in an important degree.
To procure new samples of seed grains was the first way of
combating this evil, the second being the purifying of the
introduced supplies before giving them into the hands of
the Swedish farmers. This cleaning could be performed
partly in the imported samples themselves, but had to be
combined also with the culture and multiplication wliich
usually precede the sale.

The company was founded by private agriculturists and
had consequently to serve only the needs of practice. All
educational aims and purely scientific researches are ex-
cluded from its program, but, on the other hand, its work is
based on exact scientific methods. Its botanical studies
are as broad as possible, but always in the direct service of
agricultural practice. In this respect it is to be sharply con-
trasted with most of the experiment stations of Europe and
America, and it is important to state that exactly through
this procedure the obtained results have come to be of ex-
ceptionally great significance for science as well as for prac-
tice. Another consequence of this essential feature of the
program is that its publications are destined only for the
farmers of Sweden. They are pubhshed in the Swedish

52 PLANT-BREEDING

language and deal with the results of the work. Fortu-
nately, however, the Director and his staff have, from
time to time, given short surveys of the progress realized,
and of the methods followed in securing these practical
results.

One of the means by which the young company contrived
to gain a notable influence over Swedish agriculture, was
by increasing the interest of the farmers in the purity and
the control of their seed grains. Exhibitions and distribu-
tions of samples of pure seeds, descriptions of the various
marks by which the varieties may be recognized, repeated
inspections of the fields of the station, where pure cultures
were grown side by side with the common Swedish sorts,
gradually convinced the farmers of the great significance
attached to the careful choice of their sowing-seeds. As
soon as this conviction became general, the results could no
longer remain doubtful, and, gradually, the fame of the
station increased to a degree corresponding with the aug-
mentation of the harvest.

This purification of the imported strains must evidently
lead to an exact study of the constituents of the original mix-
tures and to a comparison of the part they take in the harvest.
In the beginning, however, these were wholly obscured by
the views which were then prevalent in Germany concerning
the improvement of races among agricultural plants. It
was taken for granted that the purification of the imported
samples was simply to make them true representatives of the
variety under the name of which they had been bought,
so as to guarantee their quality to the Swedish purchasers.
Furthermore, it was desired to accHmatize the best foreign
kinds and to make them suitable to the requirements of the
soils and climates of Sweden as well as to the various de-
mands of the local industries. This part of the program,
however, was intended as an application of the German

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53

54 PLANT-BREEDING

methods of improvements to the special needs of Swedish
agricukure.

From these statements it may easily be gathered that the
importation of new and valuable kinds from neighboring
countries was, at first, one of the chief occupations of the
station. The most prominent and most renowned varieties
of the cereals of Europe were purchased and tested, the old
and common sorts as well as the newly introduced and ameli-
orated kinds. After fmding them adequate to the local cir-
cumstances, they were multiplied, exhibited and recommen-
ded and finally given to the trade. In this way, Probsteier
oats, Ligowo oats. Squarehead wheat, Victoria peas and
different kinds of barlev have been distributed. By their

ml J

culture, the agriculture of the southern parts of Sweden was
noticeably improved, and even the export of grains to Bel-
gium and other European countries, which previously had
suffered much from the deterioration of the races, could be
restored to its former degree of importance.

The influence of these new methods may best be judged
by the rapid growth of the company. Already in the second
year, it could extend its interests, which were primarily in-
tended for the southern part of Sweden only, to the whole
country. Soon afterwards, another company was organ-
ized on the same principles and with the same aims. It had
its seat at Orebro and was destined to work for the middle
part of Sweden. But after an existence of only four years,
it was combined with the Svalof company, which then (1894)
took its present name of Sveriges Utsadesforening, or Seed-
grain Society for Sweden. It entered into relationship with
the greater number of local agricultural companies and was
financially aided by them as well as by the Swedish govern-
ment, so as to be enabled to work on a largely increased scale.

Gradually the combination of the experimental and the
commercial sides of the work became too cumbersome, and

NILSSONS DISCOVERY 55

moreover brought about a kind of competition with the local
seed dealers, which was felt to be a hindrance to its further
development. Five years after its estabhshment (1891)
these considerations led to a separation of the two branches,
a separate company for the sale of the improved grains being
organized under the name of Allmanna Svenska Utsadesak-
tiebolaget or General Seed-grain Trading Company of
Sweden. This company has its seat at Svalof, too, and re-
ceives the seeds of the ameliorated varieties which the society
has produced, in order to multiply and distribute them. It
is operated constantly under the control of the seed-grain
society and thereby is enabled to keep its races uniform and
to sell them under a full guarantee of purity.

Before leaving the history of the experiment station, some
words should be added concerning its means of providing
races for different parts of Sweden. Sweden embraces a wide
range of climates, from its cold northern parts to the mild
and favorable clime of the southern provinces. Moreover,
there is a large variety of soils. Hence it is evident that the
production of good cereals for all those various parts can-
not be effected at one single point. No variety can claim to
be appropriate for a definite soil or climate before it has been
tested under the circumstances for wliich it is destined. The
work of the society is therefore twofold, and the principle has
been accepted that the varieties are produced at Svalof, but
afterward sent to other localities, according to their qualities
and their probability of success. Everywhere in the country,
the numerous local agricultural societies are co-operating
with the station of Svalof for this purpose. x\s soon as a
new race is considered especially recommendable for some
soil or some cHmate, it is sent to the locahty in question and
tested there by field cultures in comparison with the local
sorts. By this means, many valuable improvements of local
cultures have been obtained.

56 PLANT-BREEDING

With the same object in view, two branch stations have
been organized. One of them is situated at U Uuna in middle
Sweden, and the other at Alnarp in the same region but on a
richer soil. At Ultuna, for instance, the cultures of the new
Svalof Black Bell oats are attracting special attention.

During the first years of its existence, the station followed
the methods of selection and amelioration which, at that
time, were generally accepted by the breeders of central Eu-
rope. As we have seen in our last lecture, the German
breeders considered the impurities of their races as of minor
importance. They could be gotten rid of by a careful choice
of the best and most typical ears, and the saving of seed for
sowing had of course to be accompanied always by some such
kind of selection. The exclusion of inferior cars was more
or less considered as the necessary means of keeping the races
true to their standard type. Improved races, as a rule, were
more responsive to soil, manure and treatment than the local
varieties. It is, however, unavoidable that, with the straw
of the manure, some stray grains of these inferior sorts will,
from time to time, and not rarely, come onto the fields. Here
they will be content with a lesser supply of food, space and
care than the improved races, and thereby be enabled to grow
faster and multiply more quickly. It is hardly conceivable
how soon these inferior races may multiply themselves to such
an extent as to occupy large parts of the field, supplanting
the ameliorated type and lessening the harvest to a noticeable
degree. In bad years, even the wind oats which scatter
their small seeds to the winds and thereby yield nothing at
all for the harvest, may be seen to replace more than half the
stock of the fields

Under such circumstances, keeping the races pure by
means of selection is evidently a necessary part of all intelli-
gent culture. It is the first thing to be done, but it is consid-
ered hardly worthy the name of improvement. In Ger-

57

58 PLANT-BREEDING

many, real improvement was treated as a separate occupation
and was considered as requiring a large amount of study,
and the devoting of oneself to a proposed aim. The gener-
al custom was to start such experiments from the best local
or improved varieties by an initial choice of a certain number
of typical heads. Such a group of selected plants was
called the elite, and this elite had to be ameliorated accord-
ing to the prevailing demands or even simply in accordance
with some ideal model. Year after year, the best ears of
the elite group were chosen for the continuance of the strain
or family, and slowly, but gradually, its qualities were seen
to improve in the desired direction. After some years,
such a family might become decidedly better than the variety
from which it had been derived. Then its yearly harvest
would be divided into two parts, after having been sufficiently
purified by the rejection of accidental ears of minor worth.
The best ears were carefullv sought out and laid aside for
the continuance of the elite strain, but the remainder were
sown on a distant field in order to be multiplied as fast as
possible. By this means, after a multiplication during two
or three generations, its product could be used as seed grain
for the farm or sold to others for the same purpose. Each
year the ehte would, of course, give a new and better har-
vest which could be multiplied and sold in the same manner.
From this description, it may easily be gathered that an
improved variety, produced after these principles, cannot
be called a race in the ordinary sense of the word. Only
the ehte itself is a pure race, but it consists of only a small
family, cultivated on a single farm. The extensive cultures of
the succeeding years, however, are not related to one an-
other in the ordinary way of ancestors and descendants.
They are, or at least they should be, the ends of succeeding
side-branches of the elite, each branch being surpassed in
excellence by its successor, and therefore no longer deserv-

59

6o PLANT-BREEDING

ing to be kept in culture. Since only the elite can produce
the most advanced side-branches, the production of seed
grains has always to return to it or rather to be started anew
from it. No farmer should sow his own harvest, because
if he does so, he will soon be surpassed by others. Or, if
he should be able to do it without harm, it can last only for a
few years, since he cannot keep up the selection which alone
is adequate to maintain the race at its highest standard.

Contrary to the opinion of Hallett, w^ho claimed to pro-
duce his ameHorations by giving his plants large space,
ample manure and the best possible exposure and treat-
ment, the German principle was to make the selections under
precisely the same conditions as those of the ordinary field
cultures. It was assumed that changes produced by the
outward conditions of life, were only of a temporary and
and not of an hereditary nature. Hereditary qualities were
assumed to be innate and independent of environmental
influences. Only by means of selection could they be fixed,
increased or lessened, and finally changed in definite ways.
On the ground of these views, selection was the true factor
of the improvement, and since the breeder could select ac-
cording to his own wishes and ideals, it was believed that
selection was a means of changing any plant in any direction,
and to any desirable degree. By direct changes, brought
about by local and individual differences in the life conditions,
tliis selection could only be misled, since such a change
might be taken for an hereditary improvement whenever its
real cause was hidden. Therefore it was a rule to reject all
specimens which could possibly have profited by an excep-
tional amount of space, manure or light, before beginning
the real selection.

Such were the more or less clearly understood, and more
or less generally accepted views in central Europe at the time
of the establishment of the experiment station at Svalof . No

NILSSON S DISCOVERY 6i

reason to doubt their validity was at hand, and moreover, the
evidence was only scanty and widely scattered, without
affording sufficient material of facts for a thorough criticism.
The results of the English breeders were hardly accessible at
that time, and so the Svalof experiments had to begin by
following the German principle. Summing up the princi-
pal features, we may state that it commenced with the choice
of a certain number of ears, and cultivated their progeny as a
mixed family, in which, year after year, the best heads were
chosen in adequate number for the continuance of the race.

The experiment station at Svalof has accepted the prin-
ciple that the selection cultures must be made on the same
soil and under the same conditions as the ordinary field cul-
tures. Especially, the distances at which the seeds were
sown from each other had to be the same, this being a point
which had often been dealt with in another way, since by a
somewhat larger relative distance, the treatment and the
final distinguishing of the single plants is notably facilitated.
This principle has been found to be reHable, and has been
kept unchanged through all the periods of experimentation,
which have supplanted almost all others.

Moreover, the methods of testing and comparing have
been largely improved. Instead of the personal apprecia-
tion of the quaUties of the ears, accurate measurements have
been adopted. An elaborate book-keeping required the
statement of a large number of quaUties by short indica-
tions, and figures came to be preferred to descriptions. The
length of the ears was given, their form indicated by width
and breadth, and by the place where both reached their max-
imum value. The density could be measured by the num-
ber of nodes and spikelets, and in the latter, the number of
single kernels could be noted. Other valuable qualities
required separate tools and instruments, and even the degree
of brittleness had to be expressed by figures.

62 PLANT-BREEDING

By these means it was soon found possible to extend the
experiments to a previously unknown number, and, at the
same time, to obtain far larger deviations from the initial
type in a relatively short succession of generations. There-
by the breeder was enabled to collect his experience on a
scale large enough to yield the material for a full experi-
mental criticism of the whole method. The result of this
part of the work proved, however, to be not at all satis-
fying.

Of course, the first selection experiments were conducted
according to the local needs of the farmers. Among oats
the celebrated races of the Probst ei were cultivated, among
the peas the variety called Victoria, and among wheat the
squarehead sorts. Shortly before, the French breeder, Vil-
morin, had produced a new variety of oats to which he had
given the name of Ligowo oats. It was tested at Svalof,
and its introduction into Swedish agriculture has been one
of the best successes of the young station. In the same way,
two of the older varieties of barley, the "Plumage" and the
"Prentice," were recommended and soon largely distrib-
uted. The testing was always performed under strict com-
parison with the local varieties, of which, for this reason, a
considerable number were kept in culture.

In the meantime, the deficiencies of the method could not
escape observation. All those which were of a purely tech-
nical nature could be overcome, and on this side of the
problem a high degree of perfection was attained. But there
were other weak points which were related to the very foun-
dation principles of the method. Among these, the principal
one was that the continuous selection of the best specimens in
an arbitrary direction did not lead to improvement in all
cases. Quite on the contrary, success was rare; so rare,
even, that it could almost be looked upon as an exception.
The fact itself was not new, since in Germany, also, only

NILSSON'S DISCOVERY 63

in exceptional cases a real improvement had been obtained.
But, of course, usually only successful instances are pub-
lished, and concerning the remainder ordinarily no evidence
is at hand.

In Svalof, however, v^here numerous experiments of the
same lend, but with different varieties of cereals, were con-
ducted side by side, the fact could not escape observation.
Soon, the idea suggested itself that if success is an exception,
the principle involved in the method can hardly be a valuable
one, at least, not one on which the breeder may confidently
rely.

An instance may be given. As such, I choose the Chev-
alier barley, which is one of the most valuable kinds for the
brewers. In Sweden, it has the defect of being often ex-
posed to lodging or lying down. The culms are too weak,
and are thrown down by wind and rain shortly before the
time of the harvest. Great losses are usually the conse-
quence, and it was considered a distinct necessity to breed a
Chevaher barley with culms stiff enough to resist these evils,
even on the hard soils of the middle parts of Sweden. Here
the culture of this variety had been tried on a large scale,
but was given up in consequence of the defect alluded to.
In order to introduce it anew, and to restore the brewer's
industry to its former degree of development, the Chevaher
barley had to be improved and adapted to the circumstances.
This demand seemed the more proper, since elsewhere and
especially in Germany, this barley had attained the height
of its renown exactly at that time. There could not be any
doubt that it was the best kind for brewing purposes. On
this account, it was cultivated at Svalof on a large scale, and
with all possible care. It was submitted to repeated selec-
tion with the distinct purpose of giving it stiffer culms. The
results, however, did not correspond with the expectations.
The harvest remained comparatively small, and the quaHty

64 PLANT-BREEDING

was not that wliich might be expected. The cultures were
correspondingly increased in extent, and the selection made
more intense. The whole experiment was worked up to
such a degree of perfection that it could not only be com-
pared with the most renowned German pedigree cultures,
but might even be considered as a test by which the value
of the principle itself could be judged.

Notwithstanding this, the result was an absolute negative.
It was simply impossible to get rid of the propensity to lie
down. No real improvement could be reached. After
many years of hard work with steadily improved instru-
ments and methods of testing and selection, the experiment
had to be given up, since there was no ground for the hope of
finally reaching the aim.

At the same time, a considerable number of other selec-
tion experiments had been carried on. Some of them gave
the desired results, but others did not. The positive in-
stances were only few, and although they have produced
quite valuable new races, and have distinctly contributed
to the improvement of agriculture in southern Sweden, it was
clear that they could not afford sufhcient proof for the reha-
bihty of the principle.

Success remained an exception, and exceptional improve-
ments were not the aim of the work of the station. Dis-
tinct problems it had to solve. It had to free the old varieties
from definite defects, which impeded their more extensive
use. A method which would give its results in some cases
and in others not, could not be considered as involving the
principle wanted. On the contrary, the conclusion had to
be granted that in the positive cases, the result might be due
to quite other causes, and that if it were only possible to dis-
cover these, the whole system might be thrown over and
replaced by sure and more rehable principles. The Ger-
man idea that it was in the power of man to improve his

NILSSON'S DISCOVERY 65

plants in an arbitrarily chosen direction, was manifestly con-
tradicted by nature. The plant develops itself after its own
capacity, but does not suffer itself to be forced into other
ways.

The principle of slow and gradual amelioration by so-
called methodical selection was thereby condemned. The
squarehead wheat showed itself to be as little amenable to
improvement as the barley. Even the oats could not be im-
proved. The new varieties wliich were occasionally ac-
quired by the process might as well be considered as accidents.
Among them was the Princess barley, which had been derived
from the introduced Prentice barley, and which gained a
high reputation and extensive distribution. In the same
way, the Plumage barley yielded some valuable novelties.
There was no rehabiUty in the method, nor could it be dis-
covered why a result might be obtained in some cases, and
in others not. It was clear that the solution of the great
problem was to be sought in quite another way.

In the next chapter I propose to deal with the further
experiments of the station at Svalof, which led to the dis-
covery of the principle that the elementary species are the
true material for selection, and that they are numerous and
varied enough to satisfy all the present demands of practice.
In order to make this description independent of all dis-
cussions of the older principle, I will once more point out
the essential differences between the German method and
the work of the previous English breeders, as described in the
former chapter. In doing so we have to exclude the views
of Hallett, who partly participated in the ideas of his coun-
trymen and partly held the same opinion as the Germans.
The contrast now assumes this aspect: Improvement may
be obtained by selecting single excellent individuals, and
experience teaches that they will yield a constant and uniform
progeny. This is the old EngHsh principle, by means of

66 PLANT- BREEDING

which new races are not created but simply isolated from
among a mixture. The alternative principle is, that a race
may be improved and educated in arbitrarily chosen direc-
tions. The original race is thereby assumed to be pure
and uniform, and thus there is no reason for beginning with
one single individual. It is even better to start from a
handful of ears, and to select in each generation a similar
number, in order to be sure that all characters which are
not consciously considered in the selection may remain in
the average condition which they held in the original variety.

Concerning the causes of the improvement in this re-
peated selection, two contrasting views have been discussed.
Hallett assumed that variability was induced or at least in-
creased in the desired direction by his treatment. In Ger-
many the opposite view was held, and it was even assumed
that all changes induced by outer influences had no hered-
itary power at all. They were considered as delusive, and
the principle followed was to exclude them carefully. In-
ternal causes were the real source of variability, and these
had to be guided by selection. And since those internal
causes, from their very nature, were not accessible to man,
selection was considered the only real means of improvement.
It worked slowly and often did not work at all, but wherever
a success was obtained, it was ascribed to the influence of
this selection.

As I have already stated, methodical selection was as-
sumed to produce races which could only be kept up to their
high standard by a continuation of the selection. This
point was of the highest practical interest for the breeder,
since it kept the production of the seed-grains of his race in
his own hands, at least for a long succession of years, and
thereby enabled him to secure very considerable profits.
On this account it is only natural that many breeders of cere-
als of the present time still adhere to these old convictions.

NILSSON'S DISCOVERY 67

As an instance, I may cite the station for breeding cereals
and potatoes at Nassenheide near Stettin in Germany,
which is under the direction of Count Arnim Schlagenthin.
Akhough in the main it offers for sale the new races produced
at Svalof by the methods to be described in our next chapter,
it recommends the sale of the grains on the basis of the old
views of dependency on elite strains instead of simply laying
stress upon the purity of its products.

Finally, a question is to be considered which has more of
scientific than of practical interest. Though the isolation of
individuals of exceptional excellence and the methodical
improvement of races are absolutely contrasting principles,
it is evident that they do not, in reahty, need to exclude one
another. Quite on the contrary, it might be conceded that
isolation is one process, but that the isolated types them-
selves can afterwards be improved by selection. This con-
ception would lessen the difference between the opposite
views and at the same time make them comply, at least
apparently, with the idea of an origin of species in nature
by means of slow and gradual changes. Theoretically, no
objection could be made to this proposition and it would only
remain to test its value by direct experiments. Practically,
however, the proposition would be a purely hypothetical one,
instead of being derived from the experience of the breeders,
and it is manifest that these would thereby as well lose
their significance as a support for Wallace's views on the
origin of wild species.

C. THE SVALOF METHOD OF PRODUCING IMPROVED

RACES.

The criticism of the reliabihty of the German method of
race-ameUoration was part of the work during the first period
of the operation of the experiment station at Svalof. It had
not yet been conducted to a definite conclusion, when, in

68 PLANT BREEDING

the year 1890, the present Director, Dr. Hjalmar Nilsson
was appointed as sucli. With a broad conception of the
practical interests of Swedish agriculture, he combined the
conviction that only really scientific studies are adequate to
the solution of difficult practical problems. A thorough
knowledge of the laws of variability and inheritance seemed
to him to be the principal requirement for the solution of
the prevaihng problems. As we shall presently see, it has
afforded him the answer to the main questions and after-
ward led him to the estabhshment of his great principle of
correlated variabiUty as one of the principal foundations of
agricultural plant-breeding. But the interest of this sub-
ject Is great enough to justify a separate treatment, and so
we shall at present defer it to another occasion.

Before going into details, I will give a short survey of
the work, in order to facihtate its appreciation. Progress
has chiefly been achieved by the discovery of the numerous
elementary units of which the ordinary varieties of cereals are
built up. That varieties were, as a rule, neither pure nor
uniform, was a fact that could no longer escape observation,
and selection as a means of purifying the races and of keep-
ing them up to their main standard had already received
general recognition. But no agriculturist had even the re-
motest idea of the real state of their compound nature, and
not even the work of Le Couteur and Shirreff had been
sufficient to aiJord such a conception. A protean group of
types was found to constitute each so-called variety. These
types were seen to be different from one another in a pre-
viously unsuspected degree, covering a range of variabiUty
adequate to comply \vith almost all the needs of practice.
Moreover, these types proved to be constant ; they had only
to be isolated and multipUed to yield new and uniform races,
directly suitable for the farmers' purposes.

Confronted with these new facts, the current conception

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Fig. 19. Svalof Concordia pea, a most productive
erect new variety of green peas, produced at Svalof.

69

70 PLANT-BREEDING

of variability itself had to be reconsidered. It is rather a
state of polymorphy. The idea of continual changes can
hardly be connected with it. It is the existence of numer-
ous different forms, each of which is simple and almost in-
variable. The term should convey the idea of a mixture,
but hardly refers to actual changes in the constituent types.

Nilsson began his work by selecting a considerable num-
ber of samples from the varieties on the fields of the station,
but in doing so, he still followed the prevaiUng method.
Each sample was sown on a separate field plot and progress
was tested in regard to purity and quaHty. Nearly a thou-
sand lots were cultivated, but the result was as unsatisfactory
as before. Everywhere the groups were seen to be hetero-
geneous and to consist of a more or less motley mixture of
types. The samples, however, had been chosen under the
assumption that they were uniform, and it had been expect-
ed that they would yield each a uniform progeny. This
however, was not the case, and doubts arose as to the re-
liability of the whole process of selection. If the progeny
does not correspond to the mother plants from which it is
derived, how can we tell that the next selection will produce
a generation with the desired quahties?

All reliability of the selection-principle seemed to dis-
appear, when, fortunately, an accidental observation was
made which at once changed the whole aspect of the ques-
tion. Some few cultures were discovered among the thou-
sands which bore only one type. They were as uniform as
the remainder were heterogeneous. Concerning the initial
choice of the samples, an elaborate record had been kept,
and this enabled Nilsson to discover the cause of the purity
of these exceptional cases. According to the accepted
method, each sample had consisted of a certain number of
ears, which were as similar to one another as could be ex-
pected, and which were therefore, simply taken to belong

NILSSON'S DISCOVERY 71

to the same type. But, of course, the number of ears had
been different in the different groups, some being common
and represented by numerous individuals and others being
rare. Among the rarest, some types had only been met
with in one single head, and since the number of the ears
had been entered for each, it could be made out at the time
of the testing of the cultures, which among them were in
this exceptional condition.

To this accidental circumstance, combined with the ex-
act scientific method of keeping extensive records, the dis-
covery of the cause of the diversity of the cultures was due.
For precisely those cultures which were derived from one
ear only were found to be pure and uniform, all others
offering to the eye a more or less motley assemblage of forms.
Hence the conclusion that cultures, in order to be pure,
must be started from single ears. Two or more ears may
seem similar enough to be considered as representatives of
the same type, while in reality they do not afford suffi-
ciently reliable marks.

On the basis of this discovery, a distinction had to be
made between the selection of samples and the selection of
individual ears or panicles. The older experiments had
always been started from multiple samples, according to the
prevaiHng views, and it became at once clear that at least
one cause of their usual miscarrying must be sought in this
course of procedure. They must be designated as selections
of groups or of families, and could even appropriately be
denominated selections of crowds, an expression which would
at once convey the idea that the terms of selecting simulta-
neously more than one individual are intrinsically contra-
dictory.

Cc(ntrasting with this old principle, the new one was
designated as that of the separate selection or separate cul-
tures. It has also received the name of pedigree- cultures,

72 PLANT-BREEDING

but with another significance to the word than that used by
Hallett, as we shall soon see. It opened the prospect of a
new manner of operating and that at a time when the results
of the previous methods had become such as to make all
further trials almost hopeless.

As yet it was, however, only a presumption, resting on
the small evidence quoted. It was more an indication of
what could be expected than a proof of what really was.
It had first to be tested. This was done at once, and on as
large a scale as possible. It was in the summer of 1892
that the described rare uniform plots were seen, and in the
harvest of the same year a renewed search for starting-points
for new races was made. But this time each ear was kept
separate, and two or more heads were combined only when
they were gathered on the same individual plant. Some
ears were chosen as the best representatives of their varie-
ties, others as deviating from the type in one respect or
another. All in all, about two thousand ears and panicles
of different species and varieties, representing as many
divergent types as possible were selected. The grains of
each were sown on a separate plot, and next year all the
groups were descended from one single mother plant each.

The results of tliis trial greatly exceeded all previous
expectations. Almost all the numbers were seen to be uni-
form, all the offspring of a single plant being wholly similar.
Exceptions there were, but they were exceedingly rare. For
instance, among the 422 cultures of oats, 397 were uniform
and only 25 multiple. But of course it could be expected
that among so large a number of cars, some hybrids would
be met with, and others which would be only partially self-
fertilized, but for the remaining part contaminated by the
pollen of their neighbors. In either case, the progeny
would be dissimilar, and especially in the former the splitting
up of the hybrids would give rise to quite a considerable

NILSSON'S DISCOVERY 73

degree of dissimilarity. The cases of such mixed progeny
were rare enough to be considered as the consequence of
the selection of such hybrids, and special experiments have
since given sufficient proof of the truth of this assertion.
Leaving these hybrids aside, the cultures of 1893 advanced
the importance of the selection of single individuals as the
one reliable source of purity, to the rank of an experimentally
estabHshed fact.

From this fact it could further be deduced that a repeated
selection would be unnecessary. The next generation
might be expected to be as pure and as true to the type as
the first. IMoreover, the uniformity was such as to make
another selection simply impossible. All the differences
which formerly afforded the material for selection had dis-
appeared from these new strains. They were observed to
exist among the separate cultures, and allowed a compari-
son of these in exactly the same sense as they formerly had
made possible a choice in the fields. But within each cul-
ture no other differences were seen than those unavoidable
degrees in development which result from the differences
in location between the central plants and those of the border,
or between accidentally crowded or locally favored individ-
uals, and the average of the group.

These observations led to the estabhshment of the second
great principle, that of the sufficiency of the one initial
choice. After that, the newly isolated type has only to be
multipUed and to be kept free from accidental admixtures.
On this point, the Svalof method agrees with the principles
observed by Le Couteur and Shirreff, who, likewise, did not
repeat their selection. For the industrial side of the work,
this principle has a high value. In the beginning, it was
feared that the reduction of the commencement of a race to
one single head might protract its multiplication so as to re-
quire more generations to reach the quantity necessary for

Fig. 20. Svalof Pearl summer wheat, not layering, early ripening, with
full rounded kernels, that keep in the ears at harvest time.

74

Fig. 21. Ordinary Butt summer wheat, for comparison with the improved
variety of the previous figure.

75

76

PLANT-BREEDING

its ultimate distribution. Experience, however, soon showed
this fear to be unfounded, since the ehmination of all further
selection soon overcomes the incipient deficiency. In reaUty,

Figs. 22-26. Five different types of new varieties of oats, produced at Svalof.

Fig. 22. Flag-oats.

the multiplication of a separate culture may go on as fast
or even faster, than that of an old-fashioned methodical
selection.

In the fall of 1893, these new principles could be consid-

NILSSON'S DISCOVERY 77

ered as wholly established. At once they were raised to
the rank of an exclusive method. Of course, the existing
cultures could not easily be given up, but they could be
rapidly diminished. After three years, almost all the exper-
iments were of the separate-culture sort, and of older va-
rieties only a small number were kept, and destined to afford
the material for a comparison of the novelties with the types
they were called upon to replace. Since that time, the se-
lection of crowds, or even of small groups of heads, has com-
pletely been abandoned at Svalof, and all the numerous new
sorts which the station has since introduced into the trade
are derived each from a single individual. Consequently,
they are absolutely pure, and purity is for them such a matter
of course that often it is hardly mentioned at all.

Pure races, however, are by no means the sole, or even
the first, requisite of the farmer. Above all, they must have
better qualities and yield a richer harvest than the ordinar}'
varieties. Thus the question arose whether the separate-
cultures would satisfy in this respect. But even here they
were found to surpass all expectations. Of course, of two
thousand types, all cannot be excellent. But manifestly
this is not at all necessary. It is quite sufficient, if among
them, some few are found having really excellent qualities.
A careful comparison of the famihes of the year 1893
showed that their mutual differences WTre much greater
than could be surmised from the amount of variabihty ob-
served in the fields at the time of selection. Moreover, the
separate-cultures complied with the most diverse require-
ments, some being highly resistant to frost, others to dis-
eases, some being suited for hard and others for Hght soils,
some being early and others late in ripening, some surpass-
ing others by the stiffness of their culms, the length of their
ears, the number and size of their grains, and so on. Hard-
ly any demand could be pointed out, with which at least

78 PLANT-BREEDING

one of the new varieties did not comply. The experimental
fields were in some sense large exhibits on which each farmer
could seek out the types that would best suit his soil and his
local conditions.

This choice, however, had to be made at the station it-
self. It was impossible to multiply even many hundreds of
the new sorts. The best had to be chosen, and in order to
do this, all of them had to be compared with the utmost
care. A second line of work had to be set up, as important
as the first, but requiring a far larger amount of labor. The
new varieties had to be studied and tested, and to be tried
from all points of view. The study had to embrace their
whole Hfetime, and the botanical marks and biological
symptoms as well as the industrial quaUties, and their re-
quirements with respect to treatment. The botanical and
biological characters of the new sorts came first, because
they were more easily studied and because they afforded
an opportunity of reducing the number of the strains con-
siderably without the time-consuming and expensive tests
of the industrial quahties. In the meantime, all the famihes
were multiphed as fast as possible. As soon as some fell
out, the space left free was occupied by the remaining strains.
In this way, nearly the same extent of the field was sufficient
for the whole group, during a series of years. In the end,
only a few remained, but these had been tested in all
directions and found to be the very best. Of course, they
had also been compared with the ordinary unselected va-
rieties, and been proven to far surpass these. Five or six
years of continuous testing and of corresponding multiph-
cation arc usually required before the end is reached. It is
quite sufficient when some few new varieties are yearlv added
to the stock. So in the year 1901, eighteen excellent new
types were offered to the trade. Among them, were five
new kinds of wheat, six of barley, three of oats and four of

NILSSON'S DISCOVERY 79

vetches. Each new kind, of course, is given a separate
name which partly indicates its quahty and partly its origin.
As instances I may give the Svalof Grenadier wheat, the
Svalof Swan-necked barley, the Svalof Great Mogol black
oats and others. From the details given, it may easily be
gathered that the multipHcation and comparative study of
the isolated races embraces the largest part of the work per-
formed at Svalof. Besides this, the initial choice and the
starting of the new varieties is only a matter of temporary
concern. The comparative studies require the trials of
many hundreds of pedigree-cultures, and accordingly an
accurate system of book-keeping is one of the essential feat-
ures of the work. From its first isolation each culture is
designated by a number, wliich it retains until it is aban-
doned or until it is judged worthy of introduction into com-
merce. Then, of course, the number is replaced by an
ordinary name, as quoted above. The book numbers at
Svalof consist of four figures, the first of which is a zero,
which is prefixed to avoid all confusion with other numbers.
The second figure indicates the group and the two remaining
ones relate to the special sort. So a dwarf Ligowo oats is
called 0313, and another kind of Ligowo oats which was
afterward recommended as Svalof Ligowo, bore the number
of 0353.

The amount of this book-keeping is almost incredible.
In the year igoo, some 2600 numbers were in culture, partly
relating to different grains, including corn, and partly to
leguminous plants, such as peas, beans and vetches. To
these numbers must be added 138 comparative cuUurcs of
races almost ready for introduction into the trade, and
among these only twelve older ones were found, the remain-
ing 126 having all been isolated by the new Svalof method.
Further, the book-keeping was increased in the same year
by 431 numbers afforded by the progeny of mother plants

8o PLANT-BREEDING

which had been selected anew in the fields during the pre-
ceding season. The book-keeping embraces the complete
botanical description of each new sort, from its germination
until the time of the harvest, with all the details required
for the controlling of its constancy and uniformity, and for
the study of all those quahties upon which the introduction
into general agriculture will ultimately depend.

I have purposely left the hybrids out of consideration
until this time. In the beginning we saw that, although uni-
formity is the prevailing rule for the progeny of a single
mother plant, exceptions regularly occur. These have been
ascribed to the effect of accidental crosses. Until some time
ago it was assumed that crosses were of common occurrence
only with rye, the other grains fertihzing themselves. But
experience has shown that this is only an average rule, and
that everywhere in the fields accidental crosses may occur.
Their progeny arc, of course, hybrids, and these may spht
in the next generation according to distinct laws, as studied
for cereals by Rimpau and other investigators. Any char-
acter which was different in the two parents of the cross,
may thus split in the progeny of the hybrid, and in this
way new combinations of characters may arise. Experience,
however, shows that in ordinary fields almost all possible
combinations may be met with, and it is to be presumed
that at least the greater number of them are due to crosses
in previous and, perhaps, in long-forgotten years. In the
following generations, these new combinations of character
may become fixed in part of the progeny of the hybrids, and
it is a well-known fact that such constant races are the ordi-
nary results of natural and artificial crosses. Hence, we may
conclude that some, and perhaps many, of the types which
may be selected and isolated in the fields and which prove
to be constant races must be of hybrid origin.

Whenever such an original hybrid is found in the field

NILSSON'S DISCOVERY 8i

and selected for some peculiar quality, it will repeat the same
splittings in its progeny and thus be found not to give rise
to a pure and uniform race. This, however, is no drawback.
On the contrary, it often affords a means of acquiring new
and useful varieties. The selection has only to be repeated,
the hybrid group being treated in the same way as the
cultures of the original fields. For each type one ear must
be selected, and its kernels must be sown separately, Accord-
ing to the ordinary rules of hybrids, some of these separate cul-
tures will at once prove uniform, but others will repeat their
spUttings. Among these, the choice must be repeated once
more, and by continuing this process we may finally succeed
in getting all the possible combinations in constant and uni-
form races. These, though of hybrid origin, have definitely
lost the character of variability, which at the beginning dis-
tinguished the progeny of the original cross. They are
further cultivated and tested in exactly the same way as all
other separate cultures, and may yield as valuable agricul-
tural varieties as these.

The work of Svalof is not connected with the origin of
the elementary species which arc observed in the field.
This is a question of purely scientific interest. Two possibil-
ities offer themselves. Either the high degree of variability
is old and the same elementary types which are now existing
have already existed for centuries, or the production of new
varieties is steadily going on, affording a cause of increasing
variabihty or, at least, of a changing group of units. In the
first case the mixtures would be constant and only exposed
to accidental losses by the crowding out of some of their
rarer constituents. In the latter case, however, the process
must be assumed to be a slow one, and the existence of
hundreds of types is no proof of a high degree of change-
abiUty. This conclusion will easily be arrived at from the
following considerations. The ever-occurring crosses must

82

PLANT-BREEDING

have the effect of rapidly increasing the number of types,
even if ordinary mutability is slow in producing new units.
For, by tliis crossing, each new unit will become united

Fig. 23. Stiff -branched Svalof oats.

with many of the existing types and, in the end, perhaps,
with all of them. In this way, the production of one really
new unit will tend to double the number of the existing
types, and, in the cases of many garden flowers, where such

NILSSON'S DISCOVERY 83

crosses have been artificially made, the fact that one new
character by this means yields a very large number of new
varieties is universally known, and one of the most ordin-

Fig. 24. Svalof oats with spreading branches.

ary means of producing novelties. Moreover, if one new
unit may double the number of the separate types, a second
new unit may tend to increase it fourfold, a third eightfold,
and so on. From this calculation it may be seen that even

84 PLANT-BREEDING

a thousand separate types of combinations do not require
more than ten mutually independent changes. Or, in other
words, the wide range or variability observed in grain fields
may be the effect of the production of a few novelties, com-
bined with a sufficient degree of intercrossing. Hence, it
follows that one real change of some character in a year, or
even in ten or more years, must be considered as wholly suf-
ficient for an explanation of the observed variability. If we
take it that these changes appear suddenly, or in other words,
are mutations, then an ordinary degree of mutability, such
as is quite common with horticultural plants, seems to be
all that is required to explain the numerous types observed
at Svalof. The main dift'erence would be that in horticul-
ture all profitable varieties have been observed and isolated
as soon as they have appeared, but that in agriculture they
have been allowed to pass without observation, or at least,
without appreciation. Consequently, the larger horticul-
tural groups, such as asters, carnations and daliHas, now
contain hundreds of well-defined, pure and uniform varieties,
but the agricultural varieties are still almost everywhere
mixtures awaiting the process of sifting and testing.

The experiments of Svalof, however, give at least some
evidence concerning the probable origin of the variability of
the cereals. Up to this time I have described the pedigree-
cultures as constant and uniform, and only excluded the case
of the hybrids. But even within the purest races deviations
may occur from time to time, though rarely, and these may
be compared with what probably happens in the field. When
a race is started from one selected mother plant and multi-
pUed during some years so as to cover hundreds of acres, it is
ordinarily seen to keep wholly pure, all the thousands of in-
dividuals displaying the same characters and quaUties. This
is precisely the special feature and the advantage of the cul-
tures after the Svalof principle. But, from time to time, one

NILSSON'S DISCOVERY 85

single specimen among the hundreds of thousands \vill sport,
deviating in some mark from the main type. As soon as such
an event is noticed, the sporting individual is usually isolated
and its grains are saved separately.

This is practically nothing more than a new initial selec-
tion, a starting-point for a new race, which has to be isolated,
multiplied and tested in the same way as all the others, and
has at least an equal chance with them of yielding a valuable
contribution to agricultural practice. Some very good
novelties have been obtained in this way at Svalof. These
changes come on unexpectedly and all of a sudden, exactly as
ordinary mutations. No visible preparations and no groups
of intermediate forms accompany them. They are at once
quite distinct from the main type. But, like mutations, they
may be confused with the effects of accidental crosses, and
such, though very rare, are also seen to occur in the experi-
mental fields of pedigree-races at Svalof. Crosses may yield
hybrids which will spht in succeeding generations as we have
seen and whenever the result of the isolation and separate
multiplication of a sporting individual is a heterogeneous
group, it must be assumed that the deviation was due to a
cross.

On the other hand, such a cross does not necessarily
exclude a real mutation, since mutations are believed to occur
in the production of sexual cells and so may be limited either
to the pollen or to the ovaries of a mutating plant. But this
theoretical side of the question docs not, strictly speaking,
belong to our present discussion, and so it may be considered
sufficient to have indicated it. My only aim was to point out
the difficulties which here, as everywhere, are found in the
way of distinguishing between mutants and accidental hy-
brids. This, however, has reference only to the special cases,
but from a broad point of view the experimenters of the
staff of Svalof are satisfied that real mutations as well as

86

PLANT-BREEDING

accidental crosses are occurring in their pure pedigree-cul-
tures, from time to time.

Some instances may be given. Among the cultures of

r—.\

7

1

■■.-'■•■ ,\ -

Fie

-':5-

Svalof oats with bending branches.

pedigree wheat started from an initial selection made in the
year 1892, a race indicated by the book number 0608 distin-
guished itself by long and stiff culms, combined with an un-
usually good quahty of the grains. But it had two notable

NILSSON'S DISCOVERY 87

defects, hairy scales and long awns. On account of these
deficiencies, it was considered improbable that it could ever
be introduced into practice. During four years the race kept

Fig. 26. Svalof oats with weak branches.

pure and true to its characters, but in the year i8g6 one single
plant distinguished itself by the lack of awns and by a some-
what deviating size and shape of the ears. Its grains were
saved separately and produced a very heterogeneous mixture

88 PLANT-BREEDING

of types, among which some showed a new quality in that
their scales were smooth. Smooth and hairy scales occur-
red both on ears with and without awns, thus constituting
four principal types in which the remaining differentiating
marks gave races of an inferior rank. The next generation
still showed some splitting but soon the isolated types became
constant and uniform, eight of them being distinct enough
to justify a more comprehensive testing. Those which lacked
the hairiness and the awns were, of course, considered as
distinct improvements, and as such received new numbers
in the pedigree-book. Besides these two quahties, they also
had denser ears of better construction and stiffer culms, while
in other respects they had kept the excellent characters of the
parent form. Soon afterward the cold winter of 1900-01
showed them to possess an exceptional degree of resistance to
frost, and thereby elevated them to the first rank among all
the novelties of winter wheats. In concluding the descrip-
tion of this most interesting case of variation it remains to
be stated that the parent-strain from which it sprang has since
remained as pure as before, never repeating the novelty nor
producing any other.

As a second instance, a winter variety of wheat may be
chosen, which had been isolated in 1892 from the Hcrrcn-
hoff- wheat and bore the number 0516. It is distinguished
by long and narrow, smooth ears. It has an excellent quality
of grain but weak culms, and moreover, is deficient in its de-
gree of resistance to cold. It was absolutely pure and uni-
form, but produced in the summer of 1897 one single indi-
vidual with stiff culms and short and rounded ears. The
progeny of this mutant at once proved constant and uniform
and quite distinct from all existing varieties, excelling in the
marks of its original parent as well as by virtue of a high degree
of resistance to cold. It has since remained absolutely pure
and constant, has been multiplied during five years and given

NILSSON'S DISCOVERY 89

to the trade under the name of Zapfenweizen or egg- wheat,
alkiding to the curious egg-shape of its heads. The parent
form which produced this mutation sported twice afterward,
but in both cases its products were muhiple in the beginning
and could be brought to uniformity only after some split-
tings.

Besides wheat, the cultures of oats, peas and vetches are
seen to produce sports, from time to time, at Svalof. Here,
also, the sports are sudden and without preparation or inter-
mediates, each of them at once constituting a new type which
is as distinct from its allies as any new form found in the
fields. Not rarely these changes are found to relate to the
very marks on account of which the parent strain had origin-
ally been selected, thus constituting a distinct progression
of mutability in a previously determined direction.
Among oats one of the most prominent novelties of Svalof
has originated as a mutation in a pedigree-culture which had
remained quite uniform during the 8 or 10 preceding years.
It is one of the best black kinds and has, curiously enough,
been produced by a white variety.

In contrast with wheat and oats, the barley has, until now,
remained devoid of novelties. This fact is very important
from a theoretical point of view. For accidental crosses may
be produced as easily in barley as in wheat and oats. Direct
extensive experiments, made at Svalof, have estabhshed this
fact beyond all doubt. Hence we may conclude that on
the experimental fields, with their pure pedigree-cultures,
accidental crosses must be extraordinarily rare, even when
compared with the rare occurrences in ordinary fields. Evi-
dently the conclusion must hold good for wheat and oats as
well as for barley, and it speaks for the recognition of their
sports as mutations rather than as crosses. In other words,
it seems probable that wheat and oats are still in a mutative
period, Hke so many of our garden plants, but that barley is

go PLANT-BREEDING

now in a period of stability, as is the case with the larger
number of our wild species.

Summing up the main features of ^his short description
of the method of selection developed by Nilsson and his staff
at the Swedish agricultural experiment station, we may point
out the following propositions : Ordinary varieties of cereals
are built up of hundreds of elementary forms which, with few
exceptions, have hitherto escaped observation. They may
be distinguished in the fields by distinct marks derived from
their botanical characters, and will afterward prove to possess
corresponding differences in their industrial quahtics. They
have to be selected but once and afterward will be quite uni-
form and constant, with the exception of accidental hybrids
which, however, will also yield constant and pure races after
repeated selection. The purity of the races is such as to be
practically absolute, but this does not exclude the occurrence
of stray mutations by which new and valuable improvements
may be secured. The high variabihty which is commonly
attributed to our ordinary varieties of cereals consists only in
the differences among these constituents of the mixtures.
But these differences have been found to be so great as to
afford material for all desirable selections and to yield new
races for all the cHmates and soils of Sweden, for all the di-
vergent needs and demands of its various industries and even,
to a large extent, for exportation into other countries.

D. A CRITICISM OF THE PRINCIPLE OF CONTINUOUS

SELECTION.

In the biological sciences the name of Darwin is chiefly
attached to two great principles, the theory of descent and the
hypothesis of natural selection.

The theory of descent was founded by Lamarck, but
it owes its present form to the work of Darwin. By means
of immeasurable groups of facts, brought together from the

NILSSON'S DISCOVERY 91

various results of systematic research and of morphology, of
geography and paleontology, he not only contrived to con-
vince the biologists of his time, but also brought the principle
of evolution to almost universal acceptance. Especially
convincing were his proofs of the numerous adaptations of
living organisms to their environments.

The principle of natural selection was discovered by Dar-
win himself. In a general way he showed that many times
more individuals are born than can possibly survive. This
results in a struggle for Ufe, in which, apart from casualties,
those survive which are the best lifted for their special Ufe-
conditions. By this struggle the weak are crowded out, and
only the best- fitted become the parents of the subsequent
generation. This struggle may be seen at work at every
moment and on every field. The eHmination of the weaker
types by stronger ones also has often been observed. But
this is nearly always where different species were competing
with one another. Concerning the effects of the intraspecific
struggle hardly any observed facts are available. Whether
it takes an active part in the production of new species, and
in what manner it may be able to do so, is a question far
beyond our present observation.

For this reason Darwin reHed for a large part on the
methods of selection which at his time were in use both in
agriculture and in horticulture. He tried to show that the
evolution of species at large has followed the same laws that
underlie the evolution of races and varieties in culture. In
a general way he has succeeded in convincing his contem-
poraries of the vahdity of this analogy. Agricultural and
horticultural experience, however, were at that time only im-
perfectly developed, and the improvement of races, though
successful in a large number of cases, had no really scientific
foundation. It did not afford all the evidence required by
Darwin for a thoroughly reliable theory. Complying with

92 PLANT-BREEDING

the prevailing belief of the most renowned agriculturists, who
considered the breeding of races as a slow process of gradual
improvement, he proposed the same slow and almost imper-
ceptible changes as the source of evolution in nature. Since
his time experience and theory have made very manifest
progress. Especially the principle of the unit-characters,
which is the foundation of the theory of the origin of species
by mutation, leads us to the acceptance of saltatory changes
or so-called sports as most probably Nature 's way of pro-
ducing new forms.

According to this theory species are not changed into one
another, but new forms arise laterally from the old stems.
The whole strain continues unchanged and only produces
from time to time single aberrant individuals. These are
the real sources of all progress, and experience has shown,
that in the main their new characters are hereditary, and that
their progeny remains true to their new types even from its
first appearance.

On another occasion I have tried to show that in horti-
culture experience compHes almost wholly with this concep-
tion, and the historical researches of Korschinsky give
proof of the accuracy of this conclusion. In agricultural
breeding-practice the production of new races is a more intri-
cate problem. In many cases their relation to the theoreti-
cal conceptions is quite clear, in others it is still surrounded
with doubt. In my book on the Mutation theory I have ex-
plained how the obvious facts agree with the idea, but it was
at that moment impossible to remove all doubts, and so I pro-
posed to return to these questions another time. (Mut. Th.
I. p. 82.) Five years have since elapsed and new discoveries
have been pubHshed which enable us to give a far more com-
plete analysis of the agricultural breeding processes. Espe-
cially at the Agricultural Experiment Station in Southern
Sweden quite unsuspected facts relating to the variability of

NILSSON'S DISCOVERY 93

agricultural crops have been discovered as we have seen in our
preceding chapters. They are of a nature to turn over all
the old ideas concerning race-ameUoration and give proof
that the methods now generally in use in Europe are faulty
from a practical as well as from a scientific point of view.
The main discovery is that most of our ordinary agricultural
crops are composed not only of elementary species, as was
long known before, but that each cultural variety contains
hundreds of sharply definite types. These are widely dis-
tinct from one another in botanical characters as weh as in
those properties, which determine their utility from the
breeder's point of view, and thus they afford a rich material
for selection.

For this chapter I have chosen an apphcation of these
discoveries of Nilsson to a criticism of the current views
concerning the bearing of agricultural breeding processes on
the theory of evolution. Formerly I urged my readers to
be careful not to trust too much to these processes and to
make use, in scientific discussions, of the most simple and
clear cases only (Mut. Theory I, p. 59). The new facts
now at hand go to prove that the apparently simple methods
of selection have been far more comphcated than their
authors suspected. The slow and gradual working up of a
cereal to a previously fixed ideal seemed to be a process of
the simplest possible nature. In reaUty, however, it is
composed of a series of factors which the breeders them-
selves have not recognized, and which therefore it is now
often impossible to discern in their descriptions. In gen-
eral such an analysis has been made practicable by Nilsson' s
discoveries. Unfortunately it leads to a less high apprecia-
tion of the merits of the breeders (Mut. Th., p. 82), but on
the other hand it gives a stronger support to the theory of
the saltatory origin of species.

Among the results of the breeders' activity, two main

94 PLANT-BREEDING

types of races must be distinguished. In the first place,
those races which never become independent of continued
selection, and for which the seed must be produced anew
in each generation from a stock of so-called elite plants.
The other type embraces those varieties which after a short-
er or longer period of selection become self-dependent and
may henceforth be multiphed without special care.

The prototype of the first kind is given by the sugar-
beets. Here the selection works with the ordinary char-
acters of the plant, the amount of sugar, the shape of the
roots, the properties of the foliage, and other features. No
chance, no sport has produced them, they are simply taken
as the plants are offering them everywhere. In consequence,
they remain dependent on selection, and though a mul-
tiplication during one generation without renewed polariza-
tion is often unavoidable, an intervention of two genera-
tions is but seldom allowed, and the lack of selection in
more than two generations would annihilate nearly all the
effect of the whole method. This type of selection is wholly
intra-specific and has no analogy whatever with the origin
of species in nature.

The other type results in varieties which are as constant
and independent as the best horticultural sorts. In some
cases they are known to originate in the same way, by
accidental sports, as in the instance of Beseler's oats, losing
their needles. Here their comphance with the principle
of mutation is obvious. In the large majority of cases how-
ever, including the most widely known improvements of
cereals and other crops, they are said to have been produced
by the common, slow, and gradual process of selection.
All such cases are surrounded with doubt in regard to their
real origin, as well as concerning the degree of self-depend-
ency which is reached at the end. Often practical reasons
lead to the preferment of the original seed to one's own

NILSSON'S DISCOVERY 95

harvest, especially when it is difficult to keep the cultures
clean from vicinistic impurities. A race which is really
self-dependent may in this way seem to be permanently
related to the continuous selection of its pedigree. Such
races have been produced at various times by Heine in Ger-
many for rye and wheat, by Drechsler in Gottingen for rye,
by Mokry in Hungary for wheat, and in many other instances.
It is especially in Germany that this method of slow im-
provement is adhered to and has given admirable results.
One of the best known instances, and for which the histori-
cal records are the most complete, is the famous rye of
Schlanstedt, produced by Rimpau, which is now largely
cultivated all over the central part of Germany and the
northern districts of France. In the year 1876 I had the
privilege of visiting ]Mr. Rimpau on his farm at Schlanstedt
and of studying his cultures. The elite of his new rye was
standing on a small parcel out in the fields, but surrounded
by cultures of vegetables and other plants not belonging to
the cereals. These minor cultures occupied a large square,
which in its turn was surrounded by a complete range of
shrubs. Thus, the rye, standing in midst of the square, was
sufficiently removed from the neighboring fields to insure it
against possible contamination by pollen of other varieties.
On the other hand, it was given the same soil and exposure
and almost the same cultural treatment as the average cultures.
This race had been started by Rimpau nine years before,
in the year 1867. At the time of the harvest of that year he
inspected, as he told me, a large number of his r^'e fields
and selected all the ears which seemed to him to noticeably
surpass the others. He brought home a handful of them,
repeated the trial, and mixed their seeds. This mixed con-
dition in the beginning of his race has now become the
weak point, where the whole principle of his method is
open to criticism, as we shall soon see.

96 PLANT-BREEDING

The seeds were sown the next year, and in the harvest
the same selection of the best ears was repeated. Care
was taken to exclude all those which, because of some ex-
ternal condition, would have been benefited by more space
or more manure than the rest, and would have grown larger
by such accidental means. No care, however, was taken to
isolate the individuals and to sow their seeds separately,
the principle being that all the plants belonged to one race,
and that this race had to be improved. This principle of
amehorating a race without isolating its possible constituents
seemed at that period to be the right one, though now it
can scarcely be considered as scientifically correct.

Each year, in the same way, the best ears were chosen
for the continuance of the ehte strain, and after the exclusion
of all ears of minor value the remainder were sown on a
field and multipKed without further selection in order to
produce all the seed required for the sowing of the whole
farm. It took three or four years to reach this quantity.
After twenty years of continued selection this elite strain
was so much improved as to produce a race distinctly richer
than the ordinary varieties of rye in Middle Germany, and
slowly but gradually it found its way, first into the surround-
ing farms, and afterward over large parts of the country.
During this period Rimpau was thereby enabled to sell all
his harvest as seed-grain, obtaining in this way a most satis-
factory recompense for his labors. Shortly afterward the
rye of Schlanstedt was introduced into France, where it
soon overthrew the local varieties, especially in the de-
partments north of Paris. Even there it is ordinarily cul-
tivated from original seed, produced directly by Rimpau
or multiplied only during some few generations by seed-
merchants.

For purpose of criticism it is highly interesting to note
how a French agriculturist, Professor Schribaux of the

Fig. 27. A. Rye of Schlanstedt, produced by Wilhelm
Rimpau, by slow repeated selection. B. Ordinary rye.

97

98 PLANT-BREEDING

Institut Agronomique of Paris explains the conditions of
keeping the Schlanstedt rye up to its original qualities. He
says: "In order to do this, care must be taken to sow the
seeds on a field which is as far removed as possible from all
other cultures of rye. Moreover, the field should be large
and protected all around by a hedge of trees and shrubs.
Without this precaution the rye of Schlanstedt would soon
degenerate through accidental crosses with the local varieties."
Such crosses would under any other conditions be unavoid-
able and soon wholly deteriorate the race (Almanach du
Cultivateur 1892, p. 69).

From this judgment, given by an authority who has so
greatly contributed to the wealth of northern France by
the introduction of this variety, we may deduce some con-
clusions as to the constancy of Rimpau's rye. It is clear
that Schribaux takes the race to be substantially constant
and explains the necessity of continued selection only by
the impending danger of crosses with varieties of minor
value. Hence it follows that the main significance of the
pedigree-culture on the farm of Rimpau must be the same,
and that at least in later years his pedigree must have gained
a degree of uniformity, which was in no need of any further
improvements. The real act of effective selection is thereby
brought back to the first years, but how many generations
of true selection it has taken to render the rye of Schlanstedt
uniform and pure, it will of course always remain impossible
to tell. The explanation of Rimpau's success must there-
fore remain largely hypothetical. If now we try to give
such an explanation on the ground of the theory of mutation
and of the already quoted discoveries of Nilsson we may
suggest the following: At the period when Rimpau started
his pedigree, his rye fields must have contained numerous
elementary species, not observed or distinguished by him
or by any other agriculturist of his time. Among the ears

NILSSON'S DISCOVERY 99

which he selected a goodly number of these aberrant types
must of course have been represented, since he selected only
those which caught his eye by some striking and useful
difference from the main type. Of course, he sought for
ears of one and the same ideal type, having a large number
of big kernels. But notwithstanding tliis, his handful of
ears must have belonged to more than one elementary
species, the real value of which could be judged only in
their progeny. Among these units of his selection some
must have been better yielders than others and the subse-
quent selection of his twenty years of pedigree-culture must
slowly but surely have eliminated the units of minor worth.
This would result in the end in a complete isolation of the
best one of all the types, wliich he originally but unconscious-
ly selected and mixed.

Or in other words, Rimpau's pedigree culture was started
as a mixture of a number of excellent types, and his yearly
selection has gradually reduced this number, until he had
isolated and purified the very best one among them. This
point was, of course, only unconsciously reached, but then
it must have made his rye independent of all further real
selection, reducing the process to the care of excluding vi-
cinism.

If this explanation of Rimpau's process is true, it of
course holds good for all similar cases of slow and gradual
improvement of agricultural plants by selection. Thereby
it would deprive the theory of the origin of species by slight
and continuous changes of its last support in the realm of
the vegetable kingdom.

It remains to be shown that the new facts give sufficient
proof of the accuracy of this suggestion. These facts may
be grouped under three heads. First, the general occur-
rence of elementary species and their constancy. Secondly,
a comparison of the value of fluctuating variability and

lOO

PLANT-BREEDING

mutability among cereals, and in the third place, the research-
es of Nilsson, which have given the leading principle for my
suggestion.

Our first point is now becoming generally recognized.
The researches of Jordan and of Wittrock show the existence
of races for the species of the genus Viola. Other notable in-
stances are those of Draba vcrna, of Capsella Heegeri, of
the Xantliium Wootoni, a variety with half the original
number of spines on its burs, and many others.

For myself, I have had opportunities to test the constancy
of such elementary forms and in some instances even at the
period of their very first discovery. Two local evening-
primroses, up to the present time occurring only on a field
near Hilversum, where they are growing among the common
(Enothera Lamarckiana, have given proof of their absolute
constancy in my cultures. They are the O. laevifoHa and
O. brevistylis, both of which are still seen to thrive on their
small native locality. Other instances are the cruciate
form of the ordinary European primrose, (Enothera biennis
and an analogous variety of the willow-herb, Epilobium
hirsutum. Many other instances could easily be added.
The conclusion seems warranted that elementary forms
may be found in nearly all systematic species, and are as
constant as the latter have always been supposed to be.
These facts give a strong presumption that the same rule
may hold good for the rye-cultures of Rimpau.

My second point relates to the question of the part which
fluctuating variability and mutabihty may have played in
the selection-culture of Rimpau. An exact notion of the
first phenomenon, as stated by the works of Quctelet (1870)
and Galton (1889) found its way into botanical investiga-
tions about the year 1894, or nearly twenty-five years after
Rimpau started his pedigree of rye. In his time, therefore,
no distinction of this kind could be made, and it is only

NILSSON'S DISCOVERY loi

natural that he took his selected specimens to be the extremes
of ordinary variability (1867).

This point of view, and this lack of distinction between
the now so clearly contrasted processes has prevailed for a
long time among agriculturists. As an instance I may quote
the work of Willet M. Hays, now in Washington, which,
though younger than the researches at Svalof, has been
conducted independently (1899 Bull. No. 62., Agric. Exp.
Station, Minnesota). He has improved the wheat of
Minnesota by breeding from the local Fife and Blue Stem
races, some better and more yielding varieties, which have
now largely supplanted the old types. Besides his practical
results, he has given some theoretical discussions, in which
he assumes a relation of his chosen mother plants to the
fluctuating variability and considers them extremes in the
curves which constitute the law of Quctelet. "In each one
thousand plants of wheat," he says, "there are a few
phenomenal yielders, and the method of single-seed planting
makes it practicable to secure these exceptional plants, and
from these new varieties can be made" (p. 429). But
according to our present knowledge, the isolation of such
plants, if they were truly extremes of fluctuating variability,
would lead to a regression to mediocrity, as it has been
cafled by Galton, and not to constancy nor to an exact keep-
ing up of the extreme type. Therefore the supposition is
allowed that the phenomenal yielders of Hays were in reahty
representatives of distinct elementary species, which had
been hidden until his time. His method of selecting enabled
him to single them out, and his new principle of single-
seed planting, which led him to his high achievements, at
the same time pointed out the way for an explanation on
the basis of our present views concerning the different types
of variabihty.

It would take me too long to describe the methods and

102 PLANT-BREEDING

cultures of the Minnesota Experiment Station, and I may

assume that their leading principles and practical results

are well kno\\Ti. But I wish to point out, that exactly in

the principle of sowing the seeds of individual selected plants

separately. Hays gained a distinct advantage over the slow

process of Rimpau and the other German breeders. He

found, by his method, that the isolated strains are at once

constant and pure. They had only to be multiphed in

order to give a new race. Of course, the different mother

plants had to be compared in their progeny, and among a

large number of such new pedigree-races only one or two

were found to be of the very best. The remainder had to

be rejected, and only those few most excellent ones could be

introduced with advantage into the field-cultures of the

state.

If now we compare this principle of Hays with the
method of Rimpau we find that the American breeder by
one single choice isolated the very best strains and observed
them to be constant and pure. The German breeder, on
the other hand, by selecting a number of ears, must have
gotten an impure race, and needed a long succession of
years and a constantly repeated selection to attain, in the
end, the same result.

Hence we may presume that if Rimpau, in starting his
experiments, forty years ago, had had at his disposal our
present knowledge of variability, he would have sown the
kernels of his selected ears separately and selected at once
among the resulting strains the very one which now bears
the name of his farm. No continuous culture and repeated
selection would have been needed, and the seemingly slow
and gradual improvement of a race by selection would have
been avoided.

The proof of this assertion can be given, as has been
said in the beginning, by means of the magnificent experi-

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103

I04 PLANT-BREEDING

ments of Nilsson at the Swedish Agricultural Experiment
Station at Svalof . Though working only in the interest of the
practical breeder, he applied to his selection thoroughly-
scientific methods and has arrived at the clear and unex-
pected conceptions of the variability of cereals and other
large agricultural crops, which we have exposed in our
previous chapters. Summing up their contents in a few
sentences, I have first to recall the practical results and
the numerous new and productive races, which have been
originated at Svalof and are now rapidly finding approval
with the agriculturists of Sweden, and even of Germany and
other countries. For scientific purposes they give proof of
the vaHdity of the methods employed at that station, and of
the accurate nature of the principles involved therein.

Nilsson at first tried the usual German method, but
soon found that it yielded its results only in exceptional
cases and could not be applied to all the needs of the agri-
culturists (1885- 1 891). He then changed his principle and
sowed the kernels of numerous selected ears separately or
in small groups (1891-1892). The result was thoroughly
decisive, for all the parcels grown from mixed seeds gave
a mixed progeny, and only those which were derived from
one single ear each gave a pure and uniform culture. This
unexpected phenomenon was at once made the basis for
further experiments and in numerous sowings, where each
was derived from one single plant, the strains were almost
always found pure and constant. The only exceptions were
those in which a hybrid ear had been accidentally chosen.
Here of course the ordinary sphttings of hybrid progeny
were observed, but in choosing among their products, con-
stancy could be reached in many instances.

Therefore Nilsson's principle for all breeding purposes
is now to derive his strains from single mother plants. Only
such strains give pure breeds. A second discovery made

NILSSON'S DISCOVERY 105

at Svalof, and equally valuable for practice and for science,
was that of the almost astonishing richness in elementary
species among our agricultural crops. Every cultivated
species seems to embrace something like a hundred of them,
and the cereals were found to include even several hundreds
in each of the older species. Moreover the differences
between these elementary forms are so great that they cover
nearly the whole field of the wants of the practical agricul-
turist, or, in other words, by carefully searching the field,
in almost every case a plant may be found which complies
with the ideal sought for. From such a plant a pure and
constant race may be derived without other means than
that of isolating and multiplying its progeny. No special
culture and no repeated selection is needed, the only care
being to protect the race against vicinism. On the basis
of these facts Nilsson has founded an elaborate method of
selecting original plants for his pedigree-cultures and of com-
paring their value for practical purposes. But though this
process is now the prominent part of his work, it has no
direct bearing upon the signification of the methods of
Rimpau and other German breeders, and so we may leave
it here out of consideration.

Our explanation of Rimpau's method now loses its hypo-
thetical aspect. For since it is proven that the ordinary rye-
fields contain hundreds of elementary species, and among
them many of superior quahty, it is clear that Rimpau must
have had an assemblage of such types in his original hand-
ful of selected ears. To him they may have seemed alike,
but they must have been in reality of very different value.

His slow process of selecting must have singled out in
the long run, the very best one from among them. Once
isolated, this type yielded a constant race, which became
independent of all further selection.

The German breeding process has always been one of the

io6 PLANT-BREEDING

most important arguments for the prevailing selection-theory
and was of late considered its last botanical support. By
means of the discoveries of Hays and of Nilsson this
support has now been broken down, and the victory of the
theory of a saltatory origin of species can no longer be
doubted.

Ill

ON CORN BREEDING

In Europe the smaller cereals constitute the prevailing
crops, but in the United States of America, com is king,
as the phrase goes.

Yearly about 2500 million bushels of Indian corn, with
a value of $1,000,000,000, are produced in this country,
constituting almost eighty per cent of the world's total crop.
Of this more than 1500 milHon bushels are fed to cattle and
other meat- producing animals, the remainder being partly
exported and partly used for different industrial purposes.
The total number of beef cattle in the United States was
officially estimated in 1904 at 43,500,000, with a total value
of $660,000,000.

Over a hundred different commercial products and about
fifty kinds of food are derived from corn and its various
constituents, the glucose factories alone consuming over
50,000,000 bushels of corn.

There can be no doubt that corn is the most valuable
crop in the United States. Cotton, of course, bears the
palm as a money crop, but corn is the main supply of food,
directly as well as under the form of meat. No single cereal
is of the same high importance, and the agriculture of the
principal states of the Middle West is almost wholly depen-
dent upon the raising of corn.

IlHnois stands first, but Iowa, Missouri, Kansas, Ne-
braska, and some others deserve as well their name of the
corn states. In Indiana the average crop is 33 bushels per
acre, a bushel containing in round numbers 100 ears and
commonly shelling out 56 pounds.

On account of this pre-eminent importance, all questions

concerning the possible means of increasing the crop of corn

107

io8 PLANT-BREEDING

are manifestly of the highest value. Our discussion of the
different methods of improving cereals has for this reason
to be completed by an inquiry in how far and on what
points the principles discovered and elaborated in Europe
can advantageously be considered in the selection of this
dominant American crop.

In the corn states the production of corn has for
some years attained its highest degree of development,
as far as its acreage is concerned. Almost all the land suit-

Fig. 29. Breeding block of corn which has been bred for high oil content
on the farms of Funk Bros. Seed Co., Bloomington, 111.

able for corn growing has been given to this crop. Locally,
some increase of the area may still be possible, but it is of
no real importance for the total amount of the crop.

Hence, it follows that an increase of the harvest can be
obtained only by an augmentation of the yield per acre,
and since the demand for corn is incessantly increasing and
the prices are becoming correspondingly higher, the question
how to increase this yield has become a most urgent one.
The land values are constantly rising, and handsome profits are
possible, but to secure them better methods must be employed.

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109

no PLANT-BREEDING

The use of fertilizers, more careful processes of prepar-
ing the land and handling the seed and the plants, and a
proper choice of the seed-grain are the acknowledged means
by which to attain this end.

Of course, in these lectures I am concerned only with the
questions relating to variabiUty and selection. But no crop
is more responsive to careful selection of the seed than corn.
According to the condition of the land, the treatment of
the field may be of first importance, but good seed will
always add considerably to the yield, and the more so, the
better the condition of the soil and the care given to its
culture.

Some farmers are producing 60 to 70 bushels per acre
every year, wliile their neighbors are contented with an
average harvest of 30 to 35 bushels. In favorable cases the
product might easily be increased to a hundred bushels per
acre and even more.

As a rule, however, the corn yield per acre is gradually
decreasing, at least in some of the leading states. In Ohio
the period 1890 to 1899 shows a falling off of 3^ bushels as
compared with the previous ten-year period. But in Indi-
ana, where the interest in corn selection is rapidly growing,
the average yield per acre has increased during the same
time by 12.8 per cent, and in Illinois, wliich has started the
principle of individual ear selection, the yield per acre of
com has increased to 22 per cent more than in the ten years
preceding the introduction of this new method.

The recent discoveries made at the Agricultural Experi-
ment Station of Sweden will, no doubt, some day exercise
a notable influence on the American processes of corn-
breeding. In some points they are in full agreement with
them, but since they are founded on more elaborate scien-
tific methods, they may facilitate the understanding of the
processes now in use.

Fig. 31. Different types of corn. A. King Philipp, a variety of flint corn.
B. Giant yellow dent corn. C. Rice popcorn. D. Dwarf popcorn.

Ill

X12 FLAXT-BREEDING

Jn some of the bulletins of the agricultural experiment
stations, dealing with the improvetnent of com, it has been
pcjtnted out that we do not yet imdeistand many of the prin-
cifdes undedyii^ com-bieeding, but that on the other hand
it is to Ae interest <^ each corn-grower to obtain as com-
plete a knowledge on this point as possible, in order thereby
to bring the fadtess of his selecti<Hi under his controL

From a scientific point of Tiew, however, there can be
fitde doubt that flie same la^^ that govern the variability
and the sdecticMi of cereals in g<aieral contnd the corres-
ponding phrfHnfunrwna for com, too, and that the esistiiig
(fifferences are, as a £act, <Hily due to those plain and easily
lea^Toizable characters which contrast com with the smaller
cereals.

For tMs reason I propose to gjve a description of the
:.:::5 of variaMitv and the methods of sdection of com,
based on the priocijdes evolved icr cereals in my previous
cfaapteis. I diall conscieQtioushr describe the facts, but shall
rdv in their appredalion partly on the obtained results, and
r .L— h- cm. a cemiparisiHi with the Swedidi and German prin-
ciples. In doing so my chief aim is to awaken tiie interest
: >e who are in <Kie way or another ccMocemed in
: r ing, fee i srady of analogous questicms in other

:r js.

T"-v snadv of viLriiri^iiy is the bass c: al. selection-
TJiv ~ ri we are oiabled to discerr '!_ ': iizerezces and
: their po^Me industrial va^ue, t::e : :: ;~ ~v

Siii^— . Zft z- ~ our choice.

MoreoT^. rrm variabifity covers ?: "~ ~ : - -r?

:: - -. :- — — . _ :he sigmScanceof the .sir.^-, r r i-

: -. - -p ^'^'^ ^^ purpose of race-":rr j is so

— . „z.r^:i:. ihat it is <rf pre-eminent imponan^- .. aave
a jnn: ~ -^ey of the most obvioi^ r^-=.^

E^:z - - -" knows that com is or.-. .: :_. ni _;: i:i_:-i;mi

Fig. 32. A. Sweet corn, an ear with a staminate upper part and
with some few kernels in top. B, C. Parts of a tassel of flint com
bearing staminate spikelets and kernels.

"3

.114 PLANT-BREEDING

species. It embraces seven types which are different enough
to be considered by some authors as the equivalent of sys-
tematic species. Each of these groups includes a number
of varieties or sub-races, and these, in their turn, are by no
means uniform, but offer to the experienced eye an utter
chaos of indi\idual variations.

The signihcance of the main types and their most evi-
dent varieties is nowadays fairly well established, but it
is the almost inexhaustible individual variability within the
varieties that gives the material for selection.

The main types are six in number, viz. : The pod corns,
the pop corns, the flint corns, the dent corns, the soft corns,
and the sweet corns. In the pod corns or Zea Mays tuni-
cata the kernels of the ear are enclosed in husks, constitu-
ting together a pod for each single kernel. This is the form
wliich was assumed by Darwin to be the nearest relative of
the hypothetical ancestors of the whole group, since corn is
the only species in the family of the grains, which possesses
naked kernels.

The pop corn is easily recognized by the small size of
the kernels and ear and by the excessive proportion of the
horny or corneous endosperm, which, in the best varieties, is
so well developed that it wholly excludes the starchy tissues.
Tliis gives the property of popping, by which process the
kernel is burst and the contents turned inside out. The
rice pop corns, with pointed kernels, are among the best-
known races of this group.

The flint corns have a well- developed starchy tissue en-
closed by the horny endosperm. This latter varies in thick-
ness with the varieties and causes the kernels to become too
hard when dry for cattle to eat them without their being
ground. Thence, the Latin name "indurata. "

The dent corns, Zea Mays indentata, are easily recog-
nized by the indentation on their outer surface. This de-

Fig. T,^. A highly ramified ear of corn.
"5

Ii6 PLANT-BREEDING

pression is caused by the shrinkage of the starchy matter
in drying. The dent varieties are almost the exclusive corn
crop of the corn states and are of supreme value in the feed-
ing of cattle; they are more numerous than all the varieties
of the five remaining groups taken together.

The soft corns, Zea Mays amylacea, have no corneous
endosperm, as their name indicates. The kernels, however,
shrink uniformly and do not become wrinkled in drying.
This group includes some of the oldest varieties, as, for in-
stance, the mummy corns of Peru and Chile, and the very
largest-kerneled type, the Cusco.

The sweet corns, or Zea Mays saccharata, are character-
ized by their wrinkled and more or less translucent seed.
This condition, however, is not caused by the horny part of
the kernel, but by the starchy tissue in wliich the starch is
almost wholly absent. It is replaced by a sweet constituent
or kind of sugar, belonging to the group of the dextrines.
It is mainly grown for table use and for canning purposes,
the grain being canned before becoming ripe. Maine and
New York are the principal states for this culture, which,
however, extends all along the Atlantic coast.

In each of these six main groups there are a number of
varieties which are partly distinguished by the forms of the
kernels, whether broad or deep, partly by the proportion of
the horny and the starchy part of the endosperm, and partly
by many other subordinate marks. E. L. Sturtevant, in
his Varieties of Corn (U. S. Dept. of Agriculture, 1899, N.
57) enumerates 300 varieties of dent corn, 70 of flint, 60 of
sweet corn, and so on. These varieties or sub-races are
cultivated under different names, and their characters are
said to be constant and more or less sharply defined, not
changing under the influence of soil, climate, or treatment.
Among the dent corns the dimple-dented, crease-dented,
pinch-dented, and ligulate-dented may be cited as instances.

ON CORN BREEDING 117

But almost every one of these varieties is all but uniform.
They include all kinds of variations, both in the shape of
the kernel and the ear, and in the mode of growth and vege-
tative characters of the stalks and foHage. The differences
among these minor types within a given variety are often as
great as those which distinguish the varieties themselves.
As a fact, the varieties are mixtures of a larger or lesser num-
ber of constituents, the same sub-types recurring often in
more than one so-called variety.

Moreover, many of these varieties are subjected to abnor-
mal deviations from the type or so-called monstrosities,
including the most widely divergent forms. Stalked and
branched ears, male side-spikes on the ears, kernels in the
tassels, cockscomb-ears, hermaphrodite flowers, variegated
leaves, and many other features are the well-known instances.
They are without practical value, and their hereditary char-
acters have accordingly been only imperfectly studied.
Such study should not be neglected, however, since the bar-
ren stalks, which often cause enormous losses, seem to belong
to the same group and to obey, in their manner of inheri-
tance, the same laws. But with this phenomenon I shall
have to deal later.

The variability witliin the varieties is the main source of
all selection, and, as such, deserves our careful attention. The
distinguishing marks are many, but often so minute as to be
hardly fit for description. Often they are the same as those
between distinct varieties, and in such cases different varie-
ties may simply be different mixtures of mainly the same
constituents. In some cases the same varieties may even be
cultivated locallv under different names. ^Mixing of color
is the easiest indication of such a mixing of sub-types; it has
attracted the eye of the farmers for a long time, and often
led them to some kind of primitive selection, preferring a
pure color to the mixture.

ii8 PLANT-BREEDING

In selection, uniformity is one of the main purposes,
but the shape and color of the ears, their butt and tip ends,
the number and direction of the rows, the furrows between
the rows and many other points have to be considered. It
is only by an actual study of these variations that a farmer
may become familiar with all the different types. It would
be quite superfluous to try to describe them here, the more
so as we shall have to cjuote a number of instances, when
dealing with the work of selection.

Perhaps the most important discovery which has been
made concerning these minor variations, is that of their
constancy. All the kernels of a selected ear have the same
qualities, provided, of course, that cross-pollination has been
sufficiently excluded. This is easily seen in their visible or
physical quahties, but the experiments of Hopkins have
shown that the same rule prevails for the chemical consti-
tution, including the relative development of the main indus-
trial constituents. Moreover, it is true for the hereditary
qualities.

In the first place, direct experiments have shown that
neither the yield nor the quaUty of the grain is essentially
affected by choosing the seed-grains from the butt end, the
middle, or the tip of an ear. Furthermore, it is now cus-
tomary, as we shall soon see, to sow the kernels of selected ears
in single rows, each ear to a row, and by this method the
fact of the individuality of the rows has become quite con-
spicuous, A whole row, grown from the kernels of a single
ear, may produce numerous barren stalks, or weak plants,
or small ears with imperfect yield, or be excellent in strength,
productivity, and uniform in other peculiar characteristics.
This fact is now the acknowledged basis of the main prin-
ciple of com selection.

From these and many other concurring observations we
may conclude that the variability of corn within the varieties

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mentioned is of the same nature as that observed at Svalof
for the other cereals, and described in our previous lectures.
Thus the varieties are to be considered as built up of quite
numerous elementary forms, each of which is essentially
uniform and constant. The cross-pollination must, of
course, obscure this fact to some extent, but cannot annihi-
late it. As soon as such an elementary form is sufficiently
isolated and multiplied so that its progeny may fertiUze it-
self exclusively, a uniform and constant race will be obtained.
Variabihty will then be limited to the smaller, but unavoid-
able changes, which climatic and environmental conditions
will always evoke, even in the most purely bred races. The
nature of these so-called fluctuations we shall soon have to
consider, but for selection they are only of secondary impor-
tance.

The principle of selection at the Svalof Experiment
Station consists in the search for such elementary forms,
and in their isolation and subsequent comparative trial.
No purifying and no fixing, or in other words, no subsequent
or continuous selection is needed, provided the chosen ears
are not hybridized. Man cannot originate these variations,
nor can he essentially improve them. He must simply be
on the alert to recognize and isolate them and to compare
their progeny with the main strain. In the same way the
problem of corn-breeding is to recognize these elementary
races. All success depends upon finding the best among
them and on thus talcing complete advantage of the variabil-
ity already existing in the fields. Even the races with spe-
cial characters, as, for instance, those with a high yield of
oil or of protein, have, as a fact, been secured in this same
way.

Corn, however, differs from the other cereals in some
very important points. Two of them are now to be consid-
ered. One is the open pollinized condition, and the other

Fig. 35. A. Tassel of corn, flowering and producing the anthers from the
spikelets. B. Ear in the husks, producing the silks.

121

122 PLANT-BREEDING

is the large size of the ears and their enormous number of
seeds.

On a normal individual, the female or pistillate flowers
are combined on the ears, and at the time of flowering the
pistils or silks are protruded from the top of the husks. The
wind has to carry the pollen to them. The male or stam-
inate inflorescences are the tassels on the top of the stallcs.
Each flower contains three stamens, and each tassel pro-
duces about 20,000,000 to 50,000,000 grains of pollen. By
far the largest quantity of these is, of course, lost, being depos-
ited on the foHage or falhng to the ground. But a sufflcient
number are transferred to the silks to insure the complete
fertiHzation of the ears. Tliis, however, is not reached at
once, but several days are needed for the process. The silks
do not all appear at the same time, those of the uppermost
kernels being the first. Moreover, they continue growing
until a considerable length is reached. The diffusion of
the pollen mainly takes place early in the morning, when
the scales and anthers open under the influence of the rays
of the sun. Four or five days are usually required to pollin-
ate all the silks of an car.

It is evident that only a part of the pollen will fall upon
the silks of the same plant. This is called self-polhnation
or self-fertilization. The stronger the wind blows, the great-
er the quantity that drifts to other ears, thereby insuring
cross-fertilization. Pollen will drift in tliis way over long
distances, and is known to have been carried by the wind
over more than a thousand feet of surface. If kernels of one
mother ear are sown close to one another the pollen may be
transferred to the children of the same mother, and this is
called close-pollination.

The effects of cross-fertilization often can be seen when
different varieties are cultivated on adjacent fields. Some
color-varieties and the sweet corns are exceedingly liable to

ON CORN BREEDING

123

this phenomenon. In these cases
the effects may be observed di-
rectly on the ears, without await-
ing the next generation. This
is due to the phenomenon known
as double fertihzation and which
has been discovered only lately.
The endosperm, in order to devel-
op, must be fcrtihzed as well as
the germ, and this is brought
about by the tubes of the pollen
grains carrying each two male
elements or cells, one destined for
the germ and the other for the
endosperm. Hence we see that
in cross-poULnizing the endo-
sperm assumes a hybrid nature
as well as the germ. In ordinary
cases this condition docs not be-
tray itself by any visible mark.
In crossing sweet corn with dent
or Hint corn, the hybrid endo-
sperm assumes the characters of
the male parent. Thus, when an
ear of sweet corn is partly fertil-
ized by a dent corn, we shall find
on it, after ripening, some starchy
kernels among the wrinkled and
translucent majority. It is evi-
dent that the number of these
aberrant kernels will correspond
to the number of threads in the silks which are thus cross-
poUinated, and the number of the differing kernels is to be
considered a direct measure of the proportion of ahen pollen

Fig. 36. Sweet com, with
scattered starchy kernels, pro-
duced by partial cross-pollina-
tion.

T24 PLANT-BREEDING

deposited on the silk. In close proximity this number will
often surpass that of the normal kernels, and by artificial
cross- pollination all the kernels on an ear of sweet corn may
be induced to become starchy. It is a simple method of
measuring the degree of transportation of pollen by the
wind, and wherever a field of sweet corn is near a culture of
dent corn, the inspection of the ears may give us an idea of
the significance of this transportation.

All the starchy kernels on a partly cross-polHnated ear of
sweet corn have hybrid germs, since they were fertilized by the
contents of the same poHcn tube as the endosperm. By this
means the hybrid kernels may be recognized and eliminated
in such cases, and thus the strains of sweet corn are easily
kept pure of admixtures of this kind.

This wind-polUnated conchtion of corn has a great influ-
ence on the process of selection. In other cereals, whenever
a single head has been selected in the field, it is almost sure
to be exclusively self-fertilized and its progeny will at once
yield a pure and uniform race.

In corn, however, a selected ear will almost always be
partly cross-fertilized, and probably by the pollen of more
than one of its neighbors. If we could eliminate these hybrid
kernels and sow only the self- pollinated seeds, we might ex-
pect to get at once a pure and uniform race, which would need
only careful protection against foreign pollen during the first
year of its multiphcation. There can be hardly any doubt
that this conclusion, drawn from the other' cereals, would
hold good for corn also. iVt present, however, it is impos-
sible to distinguish the cross-fertilized kernels of an car from
the self-poihnated seeds, except in such extreme cases as we
have just alluded to. The only way is to sow all the seeds,
and to judge the plants when growing. In some instances
the hybrids may be recognized and thrown out before tassel-
ing, but ordinarily they will have to stand in the field until

125

126

PLANT-BREEDING

the time of husking. Part of their pollen will be carried to
the true representatives of the chosen race, and repeat the

mixture of the charac-
ters of the paternal and
maternal strains.

It is easily seen that
in the ordinary process
of selection, the result of
this open fertilizing con-
dition must be that the
choice is partly initial
and partly repeated or
continuous. The initial
choice is the main one on
which almost all further
success depends, but the
repeated choice gradual-
ly cUminates the bad
effects of the unavoidable
cross-fertilization of the
first chosen ear. The
initial choice corresponds
to the Svalof method but
the subsequent repeated
choice can be compared
with the German meth-
od, as described in my

Fig. 38. The hand polHnation of corn
in one of the breeding blocks on the farms
of Funk Bros. Seed Co., Bloomington, IlL

previous chapter.
Or to put it in other words, the pedigree on the female
side is pure and fully known, but on the male side it is impure
and only vaguely known and must be purified by repeated
selections. Fortunately in practice this difficulty is not so
great as it might seem to be, for experience shows that as a
rule there is a great uniformity in the progeny of a single ear,

ON CORN BREEDING 127

even if this is chosen from an ordinary unbred variety. On
the other hand, as we shall soon see, great care must be taken
in order to make sure that after the first selection all the sires
of the selected ears are as superior plants as the chosen indiv-
iduals themselves.

After having discussed the effects of the wind-fertilizing
conditions of corn, we have now to consider the influence of
the large size of the ears and the great number of their kernels.
This character makes the comparing of corn ears far more
easy than that of heads of any other cereal. The qualities
are more easily appreciated, and the multiplication being so
much faster, the importance of the work is greater. At the
time of husking, the ears have to be handled singly and tliis
will favor their inspection and study. Seed corn has to be as
uniform as possible, and the easy inspection of the ears will
lead to the elimination of all those ears which do not comply
with this condition, even in a pure race.

We may assume that pure races of corn, derived each from
a single purely fertilized ear, will show some degree of varia-
bility, and that this multiformity will strike us as more im-
portant than in the case of smaller cereals. With the same
degree of variabihty the smaller ears of wheat, with their mi-
nute differentiating marks, will seem to be more uniform than
a strain of corn, in which the differences are so much more
visible to the eye.

It is the ordinary or fluctuating variability with which
we have here to deal. It embraces the effects of environmen-
tal conditions on the plants, in the growing state as well as
during the ripening of the germ of the seed. In the more
striking cases these effects are well appreciated even by ordi-
nary farmers, and some instances may be adduced: Good
qualities may be due to accidental advantages, caused by
deficiencies in the neighboring plants. Whenever the neigh-
boring seeds fail to germinate, or when by some accident the

128 PLANT-BREEDING

young plants are checked in their development, the remain-
der will have more space, more sunlight, and more plant-food
than usual. Everybody knows that ears which have profit-
ed by such exceptional circumstances, are no true repre-
sentatives of their race and cannot be relied upon for seed
corn. Their excellence is not due to inheritance, they are
only personally superior without promise of an improved
progeny. Other ears may fall back from the average by
reason of unfavorable conditions, without having less value
as seed corn. It is a most interesting fact that often two ears,
especially when gathered from selected strains, apparently
may be exactly similar and notwithstanding this, give a very
different progeny when tested separately. It shows that
there is a kind of variability which has no direct relation to
inheritance, at least, not in the ordinary sense of the word.
It does not lead to racial improvement. Very little is
known, as yet, concerning the significance of the deviations
from the average type, which purely bred strains of corn may
produce by this unavoidable and inexterminable kind of var-
iability. We can state only that the characters of the single
ears of a pure race will differ somewhat from one another.
The characters are oscillating around the mean condition in
correspondence to the more or less favorable life-conditions
of the single plants. According to our experience with other
plants, the deviating ears of a pure race may possess the
power of transmitting the good yielding qualities of the strain
to the same degree as the average specimens. But, of course,
in practice, they can hardly be relied upon on account of the
always possible contaminations by foreign pollen. In all
cases where the uniformity of the ears and the kernels is show-
ing such fluctuating variabihty a choice of the best ears will
have to be made. But this choice is made in the interest of
a regular planting and a normal stand and not of a racial im-
provement by selection. It is difficult to appreciate the dif-

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PLANT-BREEDING

ference between the variability among the races and within
the races themselves, and only a comparison with the phe-
nomena observed in other plants will lead to a clear and use-
ful distinction.

The history of the breeding of corn is a very short one.
It dates from the discovery of the principle of single-ear se-
lection, ten years ago. The observation of the individuahty
of the progeny of one single ear is the basis of tliis method.
It enables us to estimate the hereditary value of an ear by the
inspection of its progeny. It is in full accord with the
methods of Hays and Von Lochow, who applied them to
wheat and rye, and with the Svalof method. It is different
from them only on account of the impurity of the fertilization
of the selected ear, as we have already described. Since
the discovery of this principle of single ear selection, com
breeding has rapidly developed and it is now holding a
pre-eminent place among the methods of increasing the yield
of this valuable crop.

Previous to 1897, Uttle was done in the way of breeding
corn systematically. It is even as in the case of the Euro-
pean cereals, where but few farmers had the idea of im-
proving their crop by selecting their seed, and became the
originators of some few ameliorated varieties. But they
did not attain to any influence upon the farmers at large.
Working only for the improvement of their cultures, they
failed to persuade others of the vaUdity and the importance
of their views.

Among these men J. L. Teaming, of Wilmington, Ohio,
began his work about 1825. He simply selected the best
ears of his field for his seed corn, and in doing so he soon
improved his strain of corn to such a degree that other
farmers secured his seed-corn for their own farms, and it
was soon imported into Illinois. There it has since been
improved by subsequent repeated selection, and the Teaming

ON CORN BREEDING 131

variety is now considered one of the best yielding sorts of
this state. Half a century afterward, in the year 1875 ,
another farmer applied the principles of cattle-breeding to
his corn. James Riley, of Thorntown, Ind., selected seed
from the ordinary white corn of Indiana in order to diminish
the number of barren stalks and of ears of minor value in
his fields. By this means he isolated a variety wliich he
called Boone County Wliite and which is now the most
popular variety of white corn in Indiana and Illinois. It is
one of the best yielders.

It would be superfluous to enter into more details. Some
crude attempts at selection, as, for instance, the separation
of kernels of different color, have been almost universal.
Besides these, the comparative testing of different commer-
cial varieties has long since been the acknowledged means
of securing the types which best responded to each special
local demand. Much improvement has been obtained in
this way, but in the long run it has not been adequate to
comply with the increasing necessity of keeping up with the
exigencies of consumption and industry. It is only since
the discovery of the prominence of breeding from single ears
that a start has been made that seems destined to change
the whole aspect of agriculture in the corn-breeding states.

The man who started this new principle was Dr. Cyril
G. Hopkins, Professor of Agronomy in the University of
Ilhnois. He proved the individuality of the ears not only
for the physical characteristics of their kernels, but also
for their chemical c[ualities. He showed that corn may be
bred by selection not only for yield, but for special char-
acteristics and value for different industrial purposes. He
succeeded in convincing the farmers of Illinois of the great
possibilities of systematic selection and improvement of
corn. The result has been the organization of a society
for the purpose of putting corn selection on a business basis.

132 PLANT-BREEDING

The Illinois Seed Corn Breeders Association was organized
in igoo, and began its work in 1901. Soon afterward,
similar associations were organized in other corn-breeding
states, and the systematic production of selected seed is
rapidly gaining sympathy among the farmers throughout the
United States. In the corn states it is, of course, the dent
corn with its numerous varieties which must be ameliorated,
but in Connecticut, Maine, New York, and other eastern
states the flint corns and the sweet corns are equally in
need of improvement. Farmers are now almost everywhere
wilHng to pay higher prices for pedigreed seed-corn, although
these commonly average double the value of ordinary seed.
Corn breeding has become a prominent part of the work of
many of the agricultural experiment stations, as well as a
special business for some large firms. Prof. P. G. Holdcn,
of the Iowa State College of Agriculture, at Ames, Iowa,
has brought the work of that station to the front rank, and
the Funk Brothers Seed Company, at Blocmington, 111.,
are pushing the selection of corn as a business enterprise to
its highest possible development.

As a rule seed-corn has to be purchased on the cob,
although the price is often nearly double that of shelled seed-
corn. In lUinois the price of a bushel, for the best varie-
ties, is in the first case $3 (70 pounds of ears), and in the
other case $2 (56 pounds of shelled corn per bushel).
The quahty of the individual ears is a criterion of the choice
condition of the crop and a guarantee for the next generation,
but the purity of shelled corn can never be wholly rehed
upon. No seed should be imported from distant locahties,
except for the purpose of experimental trials. Ordinary
unbred varieties, which consist of mixtures of minor types,
will, as a rule, change during the first years after importa-
tion, some of the constituents gaining and others losing in
their proportionate part of the harvest. Of course, such

ON CORN BREEDING 133

changes can never be accurately predicted, and therefore the
vahie of an imported variety can be determined only after
the change has been completed. Northern varieties are,
as a rule, shorter lived than southern forms, and this is one
of the main reasons why the common behef of the great
profits being secured by bringing in seed from other locali-
ties is unfounded. When one goes south for seed-corn, he
is apt to get a variety that will not mature in his locaUty,
and northern kinds will easily prove, on introduction, to
mature too early and to yield a correspondingly small crop.
As a rule, every degree north or south of a given locaUty
means eight or ten days difference in the time of ripening.
No farmer can depend on imported seed for his main crop.
He may purchase it for his breeding plot, but he may as
well select the best ears from his own fields. All trouble
incident to imperfect adaptation to the local conditions of
soil and climate can be avoided only in this way.

I am now coming to a critical description of the actual
process of corn breeding as it is performed by the majority
of the intelligent farmers of the corn states. I must, how-
ever, limit myself to the main method, which, of course, is
subject to many changes on subordinate points, according
to the special demands of each different locality.

Three main points in this process have to be considered
separately :

First. — The initial choice of ears in the field.

Second. — The comparative trial of the progeny of these
ears on a breeding plot, during the summer subsequent to
the year of the initial choice.

Third. — The continued selection and improvement of
the chosen strains.

The full appreciation of these three constituents of the
breeding process as different processes will probably, some
day, prove to be the most rehable basis for the further

134 PLANT-BREEDING

development of the practical methods of breeding. For this
reason I will now discuss them as independent processes.

Corn should be selected in the field. Early in the fall,
shortly before the time of harvesting, the farmer should go
through his fields and mark the stalks of superior quahty.
Width of blade, indicating a rich foHage as the source of the
organic constituents of the seeds, ears borne on shanks
neither too long nor too short, and on an average height
above the soil and other essential qualities should decide the
choice. At the time of husking, the cars of the marked
stalks are harvested separately, for the ultimate selection.
Since it is impossible to predict exactly the value of the
progeny from the inspection of the parent plant, it is desirable
to collect as many different types in the field as possibly.
Their real worth can be determined only in the next year.
But the selection of that year will evidently be Hmited by
the choice of the first year, and the wider this choice is, the
greater are the chances of ultimate success. Of course,
no farmer will select plants or ears of minor value, but he
should not try to select according to definite conceptions
of good qualities, but simply try to collect as many different
types as possible, leaving the decision concerning their
hereditary worth to the next season. As soon as he has ex-
hausted the whole range of the elementary constituents of
his varieties, no further field selection can be of any use, but
as long as this hmit is not manifestly reached, the fields con-
tain possibilities, which should not be neglected. In ordinary
cases it will therefore be profitable to repeat the field selec-
tion during some years.

Selection of corn is very easy, when compared with the
work connected with the selection of other cereals. The
different marks of the stalks and foliage, of the shanks of the
husks, of the ears and the kernels, are easily appreciated, and
their significance for the value of the new strains is mani-

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136 PLANT-BREEDING

fest. Each farmer can gather the knowledge and expe-
rience, which this process requires, and a few days' work in
a season may secure great profits without any notable outlay.
Of course, the greatest profits will come to those who have
a taste for the work and are willing to give it the necessary
attention. The most successful farmer is the one who
adopts scientific as well as practical business methods, and
who is guided in his breeding work by a thorough knowledge
of the laws of variability. He must be prepared to discern
the direct effects of environments from the marks of heredi-
tary qualities. He has to appreciate slight differences, in
the hope of seeing their significance increased by the culture
of the next year. By breeding, the yield per acre can easily
be increased by five bushels, and it is evident that this in-
crease is pure profit to the grower.

The field selection is, however, only preparatory work.
The real selection is obtained by the comparison of the pro-
geny of the chosen ears. All selection must be based on
performance, since the aim of the work is the improvement
of the hereditary qualities. Many an ear has been found of
excellent shape and size, with straight rows and perfect butt
and tip, with most uniform kernels of the most desirable
structure, but it has been rejected, because it lacked the
power of transmitting these qualities to its progeny. Often
of two ears chosen in the field, and exactly similar in all
respects, the one has given a generation which yielded double
the harvest of the other. The propensity to produce barren
stalks cannot be judged by the inspection of the ear, but it
becomes manifest in the generation cultivated from its
kernels. Many other instances could be given, and all of
them will point to the same conclusion, that the hereditary
qualities of an ear are a character which demands special
investigation. This investigation is the separate culture and
exact comparative trial of the generation grown from its

ON CORN BREEDING 137

kernels. It is exactly the same principle which now prevails
in the work of the Swedish Agricultural Station at Svalof.

The comparative trial of the progeny of the ears selected
in the field is made on a separate field plot, which is usually
called the breeding plot. Every corn grower should have
such a breeding plot. Here the grains of each ear are sown
in groups, so that it may be easy to compare the different
groups with one another. Two methods have been pro-
posed, the row system and the plat system. In the first, the
kernels of one ear are sown on a row by themselves, the
second row containing the progeny of a second ear and so
on. By this means the comparison of the rows is the basis
of judging the mother ears. Experience has shown that this
system is the most convenient, and it is now generally in
use. It is, however, exposed to the maximum degree of cross-
pollination and this must manifestly affect the purity of its
harvest. In the system of breeding in plats, the progeny of
each selected ear constitutes a square by itself, and thus at
least for the central stalks a high degree of pure fertilization
by the other members of the same family is insured. The
observed fact of the high degree of individuality of each
family, derived from one single ear, seems to point out the
desirability of this plat system for the first year of trial on
the breeding plot, even if the row system should be kept as
the most convenient for the subsequent years of selection.
The experience gained at Svalof would justify the expectation
of a considerable shortening of the number of years, re-
quired to reach the limit of possible purity, by the adoption
of the plat system for the first year of comparative trial.

A breeding plot usually embraces about 100 rows, each
derived from one mother ear, and in each row about one
hundred hills, planted with three seeds each. At husking
time each row is harvested separately and the total weight
of its ears is the main factor of the comparison, since aug-

138 PLANT-BREEDING

menting the yield is the most essential purpose of all breed-
ing. The comparison, of course, suffers from the cross-
pollinated condition of the mother ears, but, as we have seen,
as a rule, not to any noxious degree, and the plants grown
from such hyl^rid kernels will probably be thrown out by
the first selection. The plot should be protected as effect-
ively as possible from contamination by pollen from unbred
varieties. As a rule, it will hardly be possible to place it on
good soil at a sufficient distance from the remaining fields,
and a protection by hedges or timber will equally be too
cumbersome in ordinary cases. The best plan is to place
it in the midst of a large field of a selected strain and to sur-
round it by three or more rows, sown with the seeds of the
selected ears which remain after the preparation of the seed
corn for the main rows. The first contrivance will, of course,
not be available in the first season after starting the breeding
plot, but from the third year it will always be practicable.
In the choice of the best place, attention is to be given to
the direction of the prcvaihng winds, that they may carry as
few pollen grains from the adjacent fields as possible. It
has often been ascertained that pollen has drifted over a
quarter of a mile, and by the planting of stray plants of sweet
corn and the estimate of the number of starchy grains pro-
duced on them, some knowledge concerning this transpor-
tation of pollen could easily be secured. Dr. Hopkins has
pointed out the dangers of repeated self-pollination in the
breeding plot and recommended the detassehng of alter-
nate rows and the harvesting of the ears of these rows only,
in order to meet this difficulty, but with this question we are
not here concerned. In the first breeding year close-pollin-
ation of the progeny of the same mother ear should be appre-
ciated as a means of shortening the period of subsequent
selection; it will probably prove harmless even if a repeate 1
close or self fertilization should prove objectionable.

ON CORN BREEDING

139

The best ears of the breeding plots are divided into two
eroups, the very best of which is destined for the breeding
plot of next year, and the other for the multiplying or increase
field. Here it is cultivated and multipHcd in order to yield,
in one year, all the seed corn for the commercial fields of the
farm. By this means well bred seed is secured for the main
crop of each year from the breeding plot of two years before,

■ ^a;^'-/- i ^ -V tiiftf^j^M^

Fig. 41. Rows from ears of corn which have been self-fertih'zed and
from those which have not been seif-fertiHzed. The small rows are those
self-fertilized. On the breeding blocks of Funk Bros. Seed Co., Bloom-
ington, 111.

either for ordinary purposes or eventually in order to sell the
product of the farm as pedigreed seed-corn.

The selecting work on the breeding plot can be divided
into two parts, that before and that after tassehng. The
first comprises all those characters which may be judged on
the growing plants ; the second is mainly concerned with the
ears themselves. The first is accompanied by the extirpa-
tion or detassehng of all the stalks which at that time prove
to be of minor value and so prevents them from cross-breed-

I40

PLANT-BREEDING

ing into the remaining plants. Otherwise, at the time of husk-
ing, the ears will have been partly cross-pollinated, and no
account can be taken of this in the selection. The judging and
elimination of its effect must then be left to the next season.
From this discussion it is manifest that all selection
which can possibly be performed before flowering should be
done at that time and be accompanied by the detasseUng of

Fig. 42. Alternate detasseled rows of corn, at a later period of growth
on the breeding-blocks of Funk Bros. Seed Co., Bloomington, III.

the inferior stalks. This detasseling is done by pulhng the
tassels out and is without injury to the plant. It rec^uires
going over the field at least three times, in order to pull out
the tassels of all the imperfect plants, when they are fully
developed, but before the opening of the anthers and the
spreading of the pollen. No plants which appear broken,
dwarfed, immature, barren, or otherwise undesirable should
be allowed to mature pollen. ' The occurrence of tillers or
suckers and other characters can be attended to. Rows

ON CORN BREEDING 141

of general inferiority should be detasseled as a whole, since
in such cases it is manifest that the whole family has an
hereditary tendency to become imperfect.

The main point, however, in the selection before tassel-
ing is the occurrence of barren stalks. Barren stalks are
plants wliich do not produce a fertile ear. As a rule they
have imperfect ears and more or less developed tassels. It
is generally surmised that this barrenness is hereditary,
although to a large degree it is dependent on climatic con-
ditions. As a matter of fact, seed-corn which has been
fertilized by pollen produced from barren stalks is hable to
give rise to an increased number of useless plants. In many
cases the number of barren stalks reached as high as thirty
per cent, and it is evident from this that they are one of the
greatest sources of loss in corn growing. They are even
worse than a simple loss of that amount, since, except for
detassehng, they deteriorate the quaUty of the neighboring
ears as seed corn by their pollen. But a Httle care in select-
ing will materially lessen this enormous loss. The method
of breeding the seeds of single ears in rows has proved that
different degrees of barrenness are inherent in different fam-
ilies. Some ears produce more than twelve times as many
barren stalks as others, and for broken stalks a similar rule
of family indi\iduality prevails. Hence it is clear that rows
which are marked in this deficiency should be detasseled
as a whole, and that their ears should be excluded from the
ultimate selection. Only strains with the smallest possible
propensity to barrenness are worth cultivation. By follow-
ing these rules the per cent of barren stalks has been greatly
reduced. For instance, in IlUnois, on farms where this num-
ber reached as high as about sixty per cent, it has been re-
duced by selection, in the lapse of five years, to about ten or
fifteen per cent.

The high importance of the combating of this evil may

142 PLANT-BREEDING

justify a discussion of this principle from a scientific point
of view and a few suggestions upon the great superiority of
the row system of testing. The main point is to support
the view tliat the detasseling of the barren stallcs themselves
is only a very imperfect method, but that the same treatment
of the whole rows is what is absolutely necessary, the pollen
of the normal plants of such rows being as dangerous as
that of the barren stalks themselves. My suggestions are
based partly on my own experience with a special kind of
barren stalks, which produced neither ears nor tassels, and
partly on my experiments with other kinds of monstrosities
in other plants. For barrenness is to be considered as a
monstrosity, which, like all other monstrosities, is inherent
in a race, but is developed only in a certain percentage of
its individuals. The same monstrosity may occur in some
races only in a small per cent, being found in other strains
of the same variety in as much as 30 to 40, or even 50 and
more per cent. Evidently this holds good for barrenness in
corn, too, and the families with 30 to 50 per cent are those
which must be eliminated by selection, while only those with
a small per cent may be multiphed until the time that
strains will be discovered without any propensity to this
deviation. Ordinary monstrosities can be propagated, in
scientific experiments, as easily from the self-fertilized seeds
of the completely normal individuals as from the seeds of
the monstrous plants. There is no difference in the quan-
tity of the deviating specimens of the progeny between these
two sources of seed, the normal plants being as Hable to
give a monstrous progeny as the monsters themselves.

Some instances may be adduced. Torsions are of quite
common occurrence among teasels. I isolated a family
which produced yearly, during a long series of its biennial
generations, from 30 to 45 per cent of twisted stems. In
1900, I protected the twisted specimens from the pollen of the

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144

PLANT-BREEDING

normal ones and these from the pollen of the monstrous in-
dividuals and saved and sowed their seed separately. The
seed of twisted origin produced 41 percent of abnormal stalks,
the control seed giving 37 to 44 per cent of twisted plants.

Fig. 44. Twisted stems. A, Of a horsetail {Equisetum Telmateja). B.
of the wild teasel {Dipsacus sylveslris).

Ribbon-Hke stems or fasciations are another hereditary
monstrosity. In such a race of the hawksbeard I isolated the
normal plants from the flattened stems and gathered the seed
separately. The first gave 20 per cent, the latter 20 to 40 per

Fig. 45. Sterile corn, a special form of barren stalks without tassel and
without ear. Originated in the botanical garden at Amsterdam, 1888.

145

146 PLANT-BREEDING

cent of fasciated stems. Three seed-leaves on a germinating
plant of some dicotyledonous species are inherited in the
same way and so are connate seed leaves. Of the latter I
tried the Russian sunflower, of the former some evening prim-
roses, and quite a number of other species. As a rule, the
seeds of normal plants which in their youth had two free seed
leaves gave, after pure fertilization, the same per cent of mon-
strous seedhngs as the pure seed of the best selected deviating
specimens. Hence we may conclude that in races wliich con-
tain some kind of deviation, this is as hkely to be reproduced
from the seeds of the normal plants as from those of the
monstrous specimens. Applying this rule to barrenness in
corn, we may assume that the fertile stalks of rows which are
rich in unfertile plants are as liable to deteriorate the neigh-
boring rows by their pollen as the barren stalks themselves.

It has been claimed that the tendency of Nature is to
breed the barren stalks out, even without the intervention
of man. This is evidently false. Even if the barren stalks
were as deficient in their tassels as they are in their ears,
the laws of nature would not lead to any extirpation. Year
after year they would be reproduced by the fertile plants
wliich are derived from the same mother ears, and on the
average, probably in the same numbers. Tliis conclusion is
supported by the evidence of my tasselless barren corn,
which has been reproduced yearly from the fertile specimens
of the strain, during the years of my experiment. All these
experimental facts go to prove that the detasseling of barren
stalks is always only a half -measure, the rejection of the
entire rows being the only reUable process.

The main work of the comparison of the individual rows
is generally done at the time of harvesting or shortly before,
while the plants are ripening in the field. Strong and vig-
orous stalks of medium size, tapering gradually to the tassel,
with the ears at a convenient height and having shanks of

ON CORN BREEDING 147

medium length, should be chosen. High ears tend to mature
later, too low ears indicate earhncss in silking. Flowering
before or after the main period of tasseling, they are dis-
posed to be fertilized only incompletely. In a good stand
all the stalks should silk at the same time. A short shank
holds the ear too erect, while a long shank allows it to hang
over too far and exposes the plant too much to heavy winds.
Moreover, the long shanks are inconvenient in husking.
The suckers, the amount of leaves, and the growth of the
brace roots must be considered. The time of ripening and
the numl)er of ears on each stalk afford further differences.
Plants which may have profited by accidentally good condi-
tions, must be excluded from the comparison since they will
probably not be able to transmit their exceptional qualities
to their descendants.

Records must be made for each individual row, con-
cerning these and other valuable characteristics. The main
point, however, is the total weight of the ears of a row. It
must be determined at harvesting time. It is the one great
factor of selection, since increasing the yield is the main
purpose of the work. Of course, the rows have to be of
equal length, each planted with the same number of kernels,
but if tliis condition is fulfilled, the total weight of the ears
is the primary factor in determining the best rows.

After the husking, the characteristics of the ears and the
kernels should be considered. The comparative value of
the kernels depends partly on the demands of the planter or
planting machine, partly on their qualities for industrial
purposes. No planter can drop kernels evenly, when they
are of different sizes and shapes. Experiments with mixed
seed have always given an unsatisfactory stand, and only
perfect equaHty of kernels insures a perfect stand. There-
fore, the ears must be judged ,after this mark in the first
place. Tapering ears may have smaller kernels on the top

148 PLANT-BREEDING

end. The rows must be straight and uniform, their number
must be the same over the entire length of the ear. Devia-
tions from these rules will always result in insufhcient
equality in the grains of the seed-corn. The butts and tips
of the ears must be as regular as possible. Rough ears of
medium size with a large number of rows of kernels weigh
out the most shelled corn. The rows should fit together
closely and leave no furrows between them. The best kernels
arc full and plump at the tips next to the cob and have large
germs, indicating high feeding value. The edges should be
almost straight in order to fill out perfectly the available
space. The cob must be of the same color as the kernels,
especially in white varieties, since it is impossible to remove
small particles of the cob, and if the cob is red, the meal will
be discolored. Last, but not least, the vitality of the seeds
must be tested. This is a simple test but of the highest
importance, which even in ordinary farming no farmer can
afford to neglect. Out of a hundred seeds at least 93 to 95
should germinate. With a lesser degree of vitality the
stand in the field would be very imperfect, since each faihng
Geed, of course, causes the loss of a stalk and an ear. Per-
fect vitality insures a full stand and manifestly has the great-
est influence on the yield of the field. In many bulletins
great stress is laid on the rule, not to spend time on fancy
points. These are characters of the ears and kernels which
make a deep impression on inspection but which have no
relation to hereditary qualities, or for which at least such
relations have as yet not been proven beyond doubt.

x\fter all these and many other points have been con-
sidered and duly registered, all is prepared for the final selec-
tion. Here the main point is that the rows should be con-
sidered as individual families and that the best rows must be
chosen. No individual excellence of single plants has any
hereditary significance if they are growing in rows of less

A. B.

Fig. 46. Sweet corn. A. With straight rows. B. With oblique rows.

149

ISO PLANT-BREEDING

than average value. The entire breeding plot has been
started with the purpose of comparing the hereditary qualities
of the mother ears, and in estimating the result one should
stick to this principle. Excellent specimens in bad rows
may owe their qualities to cross- fertilization of the seed from
which they sprang, or to accidentally good environmental
conditions during their development, but in both cases they
have to be rejected.

Next comes the question, how many rows should be
selected for the continuance of the breeding culture? Of
course, only one of them can be the very best, and if it were
possible to select this without mistake, there could not be
any doubt about the validity of the principle of choosing
one single row. But the experience of the Svalof Station
shows that even for the ordinary cereals such a definite
judgment can but rarely be obtained by one year's trial.
In compKance with these considerations, practical corn
breeders usually choose ten champion rows and start the
breeding plot of the next year with their seed. Records are
kept and the origin of the mother cars of each new row can
be traced. By this means a comparison of the hereditary
quahties of the grandmother ears will be possible, and this
will prove to be very helpful in the selection of the second
year. A most complete analogy with the Svalof method
will thus lead to correspondingly valuable results.

Concerning continuous or repeated selection, many com
breeders in the United States have the same views as the
German breeders of wheat and other cereals. They sur-
mise that by careful, continued selection, definite characters
can be bred into the strains, according to the wishes and
needs of the farmers. This is the theory of slow improve-
ment, which has obtained such a large influence since Dar-
win built upon it one of the main supports of his doctrine
of evolution. In the case of the rye of Schlanstedt, described

ON CORN BREEDING 151

in our last cliapter, I have pointed out how ignorance of
the real nature of the variability of cereals has deluded its
originator. It made him assume that a slow improvement
was the effect of his twenty years of selection, but in reality
he simply gradually isolated by it one of the constituents of
his initially selected but mixed group of ears.

According to the experience of the Svalof Station, no
such slow improvement really occurs, and a single choice of
an ear followed by a separate culture of its grains is always
sufficient to secure a pure and uniform strain, provided that
cross-polHnations do not interfere with the result.

These principles must be applied to corn breeding also.
Any selected ear will give, in its progeny, a pure and uni-
form race within the hmits of its fluctuating variabiHty,
provided that it has not been contaminated by crossing.
Here we meet with the main difference in the breeding of
corn and of other cereals. With the latter cross-fertihzation
is an exception; with corn it is the rule. This explains the
necessity of repeated selection of corn without having to
assume the hypothesis of slow improvement. Repeated
selection is the only practical means of eliminating the effects
of previous crosses. It is only apparently a fixation of the
characters of the young family; in reality it is only its puri-
fying from vicinistic impurities. It is enforced because of
the conviction of the detrimental effects of self-fertilization
in com, but if experience should prove that one year's self-
fertilization is sufficiently harmless, the process of corn
breeding could be shortened in the same way as the Svalof
method may be considered as a shortening of the older pro-
cesses of breeding of cereals. An experimental test of the
value of the Swedish principles in their apphcation to corn
breeding would, no doubt, elucidate many as yet doubtful
points, and probably lead to some essential changes in the
practical work.

152 PLANT-BREEDING

Until now I have almost exclusively considered the
selection of corn for yield. But since Hopkins has dis-
covered that definite chemical constituents of the grains
can be improved also, the selection of corn for special pur-
poses has gained a noticeable significance. Of course,
the augmentation of the yield of shelled corn per acre will
always be the main care of the farmer, but the glucose
factories and the hominy mills will pay a higher price for
corn that has been improved according to their special
industrial interests.

In order to understand how this aim is reached, we must
first consider the structure of the kernels and the relative
proportions of their different parts. The kernel consists of
the germ or chip and the endosperm, enveloped by a very
tliin covering called the hull. The endosperm consists
of the starchy and the horny parts; its outer layer, of the
thickness of one cell, is the glutinous tissue, which may be
considered as an inner covering and is usually much tliicker
than the hull. The size of the germ and the relative pro-
portion of the starchy and horny parts of the endosperm
constitute most valuable varietal characters. In the starchy
endosperm the tissue surrounding the germ at the tip end of
the kernel is called the tip starch, the name of crown starch
being given to the starchy tissue at the upper end. These
parts are different in their chemical constitution. The oil
is mainly produced in the germ, and the protein mainly in
the horny endosperm. The better developed these two
parts are the richer the kernel will be in oil or in protein.
The germ contains 35 to 40 per cent of oil or from 80 to 85
per cent of the. total oil content of the kernel. The horny
endosperm contains much starch and about 10 per cent of
protein, a figure which is variable according to the varieties
tested.

From this description it is easily seen that a selection

Fig. 47- A kernel of corn cut longitudinally. H. E. Horny endosperm.
M. E. Mealy or starchy endosperm. S. Scutellum. G. G. Germ. B.
The young bud from which the stem will develop. R. Rootlet. After
Frank.

153

154 PLANT-BREEDING

for oil content may be made by the choice of cars with the
largest germs, and for protein by the selection of ears with a
well developed horny endosperm, or, since the white starch
is more striking to the eye, with a lesser development of this
tissue, which is poor in protein. This deduction has been
confirmed by the brilHant discoveries of C. G. Hopkins, of
the University of Illinois, by chemical analysis as well as
by direct breeding experiments. In the year 1896, he began
the breeding of corn with the idea of changing its chemical
contents in an experimental way, and selected seed of
white Ilhnois corn for four cUffcrent purposes: High and
low oil content and high and low protein production. In
the year 1903 he had succeeded in isolating four different
races, the average values of which differed greatly from
that of the variety from which he started. The ears with
the extreme percentage of these substances have been picked
out by a chemical analysis of two longitudinal rows of
kernels for each ear, but their brcechng abihty has had to
be studied in their progeny by the row-system, as described
above. The result was the isolation of high and low oil
races, which averaged 6.96 and 2.62 per cent, and of liigh
and low protein races containing 14.13 and 6.98 per cent.
It is evident that by these most remarkable experiments the
possibilities of the breeding of corn for special purposes has
been demonstrated, and the value of this fact for large in-
dustrial concerns can hardly be overestimated.

For experimental tests and commercial purposes the dif-
ferent parts of the kernels can be more or less accurately
separated. This is done by softening them in water and
then passing them into mills. First the hull is removed, the
germ is freed and the starch body broken up. Water being
used, the germs, which are lighter in weight, rise to the
surface and are separated. The remaining mass is once
more milled or ground and brought into a very fine condi-

155

iS6 PLANT-BREEDING

tion. By means of silk bolting cloths the hull or bean is
sifted out, and the starch, wliich is heavier than the gluten,
sinks to the bottom. Starch is the basis of a large number
of products, as for instance, glucose, grape-sugar, dextrine,
and gum. Among them, glucose is the most important,
next to the starch itself. The oil is isolated from the germs
by pressure after drying and grinding them to a fine powder.
The residue constitutes the corn cake and corn meal which
is used for feeding live stock. The oil itself is used by paint
manufacturers, soap makers and for the production of
rubber substitutes, among which the corn rubber or vul-
canized corn oil is one of the most important. The hominy
mills separate the hulls and germs from the hominy, which
chiefly consists of the horny part of the kernel, with more
or less adhering starch. Separated in pure form and re-
duced to a coarse powder, the hominy is called grits, the
white starch being put on the market as corn flour or break
flour.

The increase of protein is of high value, inasmuch as
corn is relatively deficient in this substance and not a satis-
factory food for young animals, except when fed in combi-
nation with other nitrogenous feeding stuffs. Protein is
several times higher in price than corn itself, and conse-
quently the stock feeders want varieties which are richer in
protein than the present ones. Any increase of the protein
content by selection will make corn more valuable as a food
for live stock. It is easily seen that even a slight improvement
in this direction would be of tremendous importance. And
in the same way there now exist markets for many different
kinds of corn. Besides the products already named, whiskey,
commercial alcohol, cellulose for coffer dams in battle-
ships, smokeless powder, and many other commodities are
manufactured from corn. But since by far the largest
quantity of corn is fed to cattle and other meat- producing

ON CORN BREEDING 157

animals, the main purpose of the farmer must always be,
next to the increase of yield, to improve the protein and the
oil. For, to put it in a few words, protein is a muscle form-
er and oil is the fat producing material. From this point
of view corn breeding should always embrace both c^uantity
and quaUty.

Corn breeding is a new industry. It is hardly older than
ten years. But it has developed at once on a commercial
scale. Experience proves it to be highly profitable, and
the conviction is rapidly spreading that no corn grower
can afford to be ignorant of its principles and its results.

Fig. 49. Luther Burbank of Santa Rosa, Cal.

158

IV

THE PRODUCTION OF HORTICULTURAL
NOVELTIES BY LUTHER BURBANK

A. METHODS AND MATERIAL

The commercial catalogues of the horticulturists contain,
yearly, a certain number of novelties. Some of these are
introduced from foreign countries, others are due to acciden-
tal sports, but many are the results of artificial improvements.
They are produced either by nurserymen or by private per-
sons who charge the seedsmen with their sale. As a rule,
this production of novelties is a subordinate matter. It is
very rare to find a man who devotes his wdiole life and all
his energies to the introduction and production of new,
beautiful or useful, horticukural plants.

Such a man is Luther Burbank of Santa Rosa in Cahfor-
nia. He is a nurseryman, but has no nursery in the ordinary
sense of the word. He is a tradesman, but sells nothing
besides his novelties, and these only to other dealers who will
multiply them and offer them to the general pubUc. His
aim is not the accumulation of wealth, but to contribute to
the welfare of other men by giving them better food, better
fruits, and more beautiful flowers. He is especially interested
in the production of cheap ornamental plants for private
gardens, in order to cUsperse their enjoyment as widely as
possible. He is not engaged in pure scientific research, but
of late he has consented to have his methods and cultures
pubHshed, that they may become a guide for other men in
their work along the same line. The Carnegie Institution
of Washington has accorded him an annual grant of $10,000
for ten years, thus enabhng him to extend his cultures on as
large a scale as is possible for the work of one man. jMore-

159

i6o PLANT-BREEDING

over, the Institution will take in hand the recording of the
history of his experiments and thus create a source of practi-
cal and scientific information of the highest importance upon
man}' questions of plant-breeding.

Such a standard work is the more needed, since the
methods and results of European horticuUurists, are, as a
rule, accessible to American breeders only with difficulty.
Burbank has had to rediscover many of the rules and prac-
tices which in Europe were more or less universally known.
His science and methods arc his own work, although in
comparison with those of other horticulturists they do not
contain essentially different procedures. It is a most interest-
ing study to go into the details of such a comparison, espec-
ially since, by the same principles, he has obtained such
striking new results. If his work does not enlarge our
knowledge of the general rules, as it is not intended to do,
it, at least, provides us with such numerous illustrations that
a description of his experiments, even if but brief and incom-
plete, may be considered as a review of almost the whole
field of horticultural plant-breeding.

From this point of view I shall now give a survey of
Burbank 's work. In doing so it is not my aim to recom-
mend his fruits or his flowers. They recommend them-
selves, and their world-wide appreciation gives the best
proof of their liigh value. I am concerned only with the
methodological side of the work, and my main aim is to de-
scribe such details as will best contribute to the estabhshment
of the full agreement of Burbank 's experience with the agricul-
tural methods of Nilsson on the one side, and with the latest
results of biological investigation on the other.

Luther Burbank was born March 7, 1849, in Lancaster,
Mass. His father was of English and his mother of Scottish
ancestry. He was reared on a New England farm and
indulged in the breeding of American grapes and of new

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i62 PLANT-BREEDING

potatoes, which was quite a common pursuit in Massachu-
setts about the year 1873. He succeeded in raising some
new varieties of potatoes in that year, multiplied them
during two succeeding summers and offered them for sale
to the well known seedsmen, Messrs. J. J. H, Gregory &
Son at Marblehead, Mass. They selected one variety
among the three he had offered and paid him Si 2 5 for it.
Tliis happened in the summer of 1875, and in September
of the same year, Burbank left Massachusetts and settled
at Santa Rosa, CaHfornia, partly on account of his health,
partly on account of the bright prospects which the chmate
of that part of California offered him for his most beloved
occupation, the improvepient of plants. For at Santa Rosa
almost all the garden plants, which require greenhouses in the
eastern states, can be cultivated in the open, and therefore
on a much larger, or even on an almost unlimited scale. As
an instance, I mention the Amaryllis.

In the beginning, Burbank rented a small nursery near
Santa Rosa, and cultivated market flowers and small fruits,
but had to look for work on other farms also, in order to
gain money enough for maintenance. It was only after 13
years, in 1888, that he had saved enough to buy liis present
farm. Here he organized a large nursery and soon accumu-
lated a small capital, which enabled liim to sell out his busi-
ness, in the year 1890, and to devote Ms whole life to the
introduction and production of novelties. Three years
afterward (1893) he published liis first catalogue on "New
Creations in Fruits and Flowers," wliich gained for him
a world-wide reputation and brought him into connection
with almost all the larger horticultural firms of the whole
earth.

In 1905 he accepted the Carnegie grant and was appointed
an honorary lecturer on plant-breeding at the Leland Stan-
ford Junior University. Here he delivers two lectures a

i63

ib4 PLANT-BREEDING

year before a score of advanced students and professors,
illustrating his new creations by means of specimens and
photographs, and explaining the experiments by which they
were won.

In the meantime, the potato which he sold to Messrs.
Gregory had proved to be a great success. It had rapidly
increased in importance and supplanted many of the older
cultures. According to an official statement of the United
States Department of Agriculture at Washington made a
few years ago, this Burbank potato is adding to the agricul-
tural productivity of the country an annual amount of
$17,000,000. In the eastern states it is cultivated alongside
other varieties and is often indicated by local names in-
stead of Burbank's name. But along the Pacific Coast,
from Alaska to Mexico, it is now the standard of excellence
among potatoeSo In fact, it is almost the only variety cul-
tivated in Cahfornia, where the culture of potatoes for
cattle feeding or for factories is of hardly any importance.
Its tubers are of a large and (what is more important)
almost uniform size.

The evidence which is set forth in this discussion, I
gathered mainly during my visits to the Santa Rosa and
Sebastopol farms of Burbank, where he was so kind as to
explain his cultures to me and to answer all my questions
about them. I visited him twice during the summer of
1904, and had the privilege of a four-days' intercourse with
him in July, 1906. Of course, I had prepared myself for
these visits by studying the magazine articles on his work
pubUshcd during the last few years, and among which
those of E. J. Wickson in Sunset Magazine may be cited as
the most complete and the most reliable. Wherever pos-
sible, however, I submitted the statements once more to my
host, asking him such questions about them as would meet
the doubts which might offer themselves from the standpoint

i65

i66 PLANT-BREEDING

of a biologist. As a rule, the answers covered my wishes
and led to the conclusion that notwithstanding the widely
divergent, and on some points quite opposite, methods the
main results of practice and science are the same.

In order to understand the kind of evidence which will
be discussed here, it is necessary to have a clear idea of what
a visitor can see on the farms. As soon as Mr. Burbank has
originated a new kind of useful or ornamental tree, flower,
fruit, or vegetable, he sells it to one of the great seedsmen,
florists, and nurserymen with whom he is in constant relation-
ship. They take the whole stock, multiply it and offer it
to the trade. They buy the exclusive right of selling the
new variety, and nothing of it is left on the farms of Burbank.
Hence it follows that a visitor cannot expect to have a sur-
vey of the achievements that have already been made. There
is no collection of these in living condition. One may
study the commercial catalogues of Burbank or inspect his
numerous photographs, but the perfected varieties themselves
are no longer there.

On the other hand, the visitor to the experiment-farms
will become acquainted with the novelties destined for the
immediate future. Burbank will explain to him his aim and
his hopes as well as the methods by wliich he expects to
fulfil them. The future, however, is uncertain, and the
real value of a novelty can be judged only after some years
have elapsed after its introduction into general culture.
The spineless cactus opens the brightest prospects for the
cultivation of the arid deserts, but the trial to determine
whether it will succeed under those unfavorable conditions
and will reward the expenses of its cultivation must still be
made. So it is in many other cases too. Burbank himself
is the most exacting judge of his productions and insists
that they shall stand all tests of culture and trade and shall
survive such exacting trial or perish.

BURBANK'S HORTICULTURAL NOVELTIES 167

From tliis discussion it may easily be seen that my evi-
dence relies, for a large part, on experiments which are not
yet ftnished and the ultimate result of which cannot yet be
estimated. For the description of the methods used, this
is of no importance, and in many cases the older experiments
with their practical results will have to be alluded to.

Burbank's first catalogue was published in 1893. It is
now 13 years old. The varieties described therein are, of
course, older, but they are only a small number in comparison
with his present stock. The larger part of liis experiments are
younger, and only a few of his pedigrees cover more than ten
years, as, for instance, those of the plums.

A special feature of Burbank's work is the large scale
on which his selections are made. It is evident that in a
variety of mixed condition, or in the offspring of a hybrid, and
even in oidinary fluctuating variabiUty the chance of finding
some widely divergent individual increases with the number
of the plants. In some hundred specimens a valuable sport
can hardly be expected, but among many thousands it may
well occur. The result depends largely upon these great num-
bers. In one year he burned up sixty- five thousand two and
three year old hybrid seedhng berry bushes in one great bon-
fire, and had fourteen others of similar size. He grafts his
hybrid plums by the hundreds on the same old tree, and has
hundreds of such trees, each covered with the most astonish-
ing variety of foliage and fruit. Smaller species he sows in
seed-boxes and selects them before they are planted out,
saving, perhaps, only one in thousands or ten thousands of
seedlings. Thornless brambles, spineless cacti, improved
sweet grasses (Anthoxanthum odoratum), and many others
I saw in their wooden seed-boxes being selected in tliis way.

The same principle prevails in the selection of the species
which are submitted to his treatment. Here, also, the result
depends chiefly upon the numbers. He tries all kinds of

i68 PLANT-BREEDING

berries and numerous species of flowering plants. Some
of them soon prove to be promising and are chosen, others
offer no prospects and are rejected. The total number of
the species he has taken into his cultures amounts to 2,500.
The hst of the introductions of last year shows 500 species,
mostly from South i\merica and Australia. Formerly he
often made excursions, in order to collect the most beautiful
wild flowers or the best berries of Northern California, but
for several years he has had no time to spare for this work.
He has two collectors, who collect only for him, and many
correspondents who send valuable bulbs and seeds, from time
to time. One of his collectors travels in Chile, the other in
Australia, preferring the regions in which the chmate cor-
responds best with that of Santa Rosa. The Australian
plants are usually sent to liim under their botanical names,
the South American often without any names at all, only
the date and locality of collection being indicated. This
insufficiency of denomination is of no importance at all for
the practical work, but often diminishes the scientific value
of the experiment, as for example, in the case of the spineless
cactus. The thornless species with which he crossed the
edible varieties have been sent to him from Mexico and else-
where without names, and they have been ehminated from
the cultures as soon as the required crosses have been made.
Hence it is evident that a scientific pedigree of liis now re-
nowned spineless and edible cactus will always remain
surrounded with doubt as to the initial ancestry.

Besides his collectors in other countries and his corres-
pondents widely scattered through the United States, he
is constantlv on the lookout for odd sorts of fruits or flowers,
in order to combine them with the existing varieties. He
procures seeds from the nurseries of all countries, from
Europe and Japan as wefl as from America. He brings
together, in each genus, as many species as possible before

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I70 PLANT-BREEDING

starting his crosses. Of Asclepias I noted about 20 species
on a plot, of Brodiasa four, of Rhodanthe, Schizanthus, and
the fragrant Tobacco all the best and newest European
varieties and hybrids. Many other instances will be given
in the special descriptions. Among grasses he is now trying
species of Lolium, Stipa, Agrostis, and Anthoxanthum,
partly for forage and partly for lawns. Of evening prim-
roses he had received a large flowered form of the creeping
white CEnothcra albicaulis, which he has now selected
along with other small and large flowered yellow primroses.
Many wild species afford deviations, which are ordinarily
considered as monstrosities, but which in his hand may be
improved to yield valuable ornamental plants. He showed
me a beautiful yellow papaveraceous plant, the Hunnemannia
fumariasfolia from Mexico, which in some specimens
doubled its flowers on the outside instead of within, in the
same way as some Gloxinias. Many other introduced de-
viations and hundreds of beautiful species I saw, but there
is no reason for mentioning their names here. Very often
a wild strain suppHes some valuable c|uality or perhaps only
the vigor of growth which fails in its cultivated allies. Many
a weak race was made strong by tliis means.

Among the species and varieties introduced from foreign
countries some proved to surpass the corresponding American
forms without needing any improvement. In this way very
valuable contributions to American fruit culture have been
secured. In the beginning of his work, a Japanese agent
one day sent him some plum pits. From these he grew two
varieties, which he has since introduced under the names of
Burbank and Satsuma plums. The first of them was named
for him by the United States pomologist at Washington.
It was exceptionally suitable to American concUtions and
has justified its selection by its present wide distribution
and economic value. The Satsuma plum is now commonly

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172 PLANT-BREEDING

cultivated in California and is a most delicious preserve on
account of its sweet flesh and small pits. The Burbank
plum, on the other hand, is one of the best and most popular
Japanese plums throughout all the United States, it is early
and heavy bearing, free from insects and diseases, and a
market fruit of large size and attractive color.

Other species needed only sowing on a large scale and a
selection of the best individuals, and could then be intro-
duced without artificial improvement. The common French
prune, of which California has produced one hundred and
fifty millions pounds of dried produce in a year, is a small
fruit and late in ripening, although it is rich in sugar. In
order to enlarge the size and to change the time of ripening,
Burbank sowed large numbers of seeds of this French prane
d'Agen, grafted the seedlings on older trees in order to force
them to yield their fruits soon, and finally chose among the
thousands of grafts the type which is now known as the
sugar primes, a large fruit ripening a month earhcr and
proHfic in bearing. In the same way, the crimson rhubarb,
or mammoth pie plant, was secured which is now grown on
a large scale all around Los Angeles, whence it is shipped,
during the wdnter months, to the markets of New York.
It is a continuous bearer throughout a large part of the year
and has a pecuharly delicate flavor. It was sent to Santa
Rosa by Messrs. D. Hay and son, nurserymen in Auckland,
New Zealand, about fourteen years ago. Burbank sowed the
seeds on a large scale, and selected the best type for intro-
duction as soon as he perceived its excellent quaUties.
Among flowers, the Australian star flower or everlasting
(Cephalipterum Drummondii) is now being introduced after
only a few years of multiplication and selection. It is a
composite, and its apparent flowers are, in reahty, flower
heads, the bright red color of which is due to the bracts of
their involucres, as m other species of everlastings. It is

Fig- 55- A hybrid walnut (Jitglaiis Calijoniica nigra), reaching double

the height of ordinary trees.

173

174 PLANT-BREEDING

recommended for millinery purposes and may supplant a
large part of the trade in artificial flowers. I admired, on
each of my three visits, the large beds full of the shiny red
flowers, and saw the selection of the largest and brightest
specimens going on.

The main work of Burbank, however, consists in pro-
ducing new varieties by crossing. The aim of crossing is
the combination of the desirable quaUties of two or more
species and varieties into one strain, and the elimination of
the undesirable characters. In the most simple cases this
can be produced by one cross and without selection; but,
ordinarily, many crosses and the production of a more or
less chaotic progeny are required, and selection has to decide
what is to Hve and what is to be rejected. It is a well known
fact, discovered Ijy Koelreuter and Gartner and confirmed
by numerous other scientific hybridologists, that hybrids
often surpass both their parents in the vigor of their growth
and the profuseness of their flowering. Taking advantage
of this rule, in more than one instance Burbank has pro-
duced hybrids of extreme capacities. The most astonishing
instances are afforded by his hybrid walnuts. In the year
1 89 1, he crossed the English walnut and the CaUfornian
black walnut and afterward planted a row of them along the
road before his residence. At the time of my first visit, six
gigantic trees were seen growing. They had reached twice
the height and size of ordinary walnut trees. Three of
them he has since been compelled to cut down, because they
increased too rapidly. This summer (1906) I saw the three
remaining specimens, 80 feet in height and 2 feet in diameter.
He showed me sections of the cut stems. Their wood was
of a fine grain, very compact and of silky appearance. The
annual layers measured about 5 cm., a most extraordinary
thickness; Fast growing trees are usually of soft grain, but
these hvbrid walnuts have a wood as hard as that of the

BURBANK'S HORTICULTURAL NOVELTIES 175

ordinary species. Byrccrossing
them the quahtics of the wood
have been still further improved,
and selection in tliis direction
produces a broad variety of
hard and soft, coarse and hne,
plain and beautifully marked,
straight and wavy grain. In
driving me to his Sebastopol
farm, he pointed out an enor-
mous walnut tree in one of the
gardens along the road. It far
surpassed all the surrounding
trees, though many of them
were older in age. It is a hy-
brid between the native Cah-
fornia black walnut and the
New England black walnut.
It is, next to the redwood and
big trees, perhaps, the largest
tree and the fastest grower I
ever saw.

Another tree which displays
the vigor of hybrids is the
Wickson plum. It is a httle
more than ten years since Bur-
bank distributed the first grafts
of this variety, and it was the
first of his plums to make a
deep impression on Californian
fruit growers. It was produced
by crossing the above named
Burbank plum with the Kelsey,
both parents being varieties of

Fig. 56. Extreme variability
in tlie size of seedlings of hybrid
walnuts in the second generation.

176 PLANT-BREEDING

the Japanese Prunus triflora. The flesh of the Burbank
is red, that of the Kelsey being dull pink and green.
The special merit of the breeder Ues in the choice of the
parents from which to produce his hybrid. The Wick-
son plum is, at present, most largely grown in California
for sliipping purposes on account of its high durabihty.
It has the unique heart shape of the Kelsey, but the flesh
of the Burbank, a rich garnet and yellow color, a large size,
and a perfect shape. It is ver}' juicy and deUcious, but its
firm skin insures good shipping and keeping quahties. Its
first sales in Chicago made the record for plum prices in the
United States. It is widely distributed over the world,
though somewhat less hardy than other varieties. It has the
best quahties of both parents and in many respects surpasses
both of them. It is one of the best illustrations of what can
be obtained in a single crossing by a man who thoroughly
knows all the qualities and characters of liis trees and how
to combine them, and who is guided by this knowledge in
the choice of the parents for his cross.

It is exceedingly difficult to gain a correct idea of the
influence which the introduction of such novelties can have
over the horticulture of some definite country or state. The
Burbank, Satsuma, Sugar, and Wickson plums are now
largely cultivated in California as well as elsewhere. They
have partially supplanted old varieties and have, also, been
the means of increasing the acreage devoted to plum culture.
But it is manifest that the change of varieties requires the
regrafting of the orchards and cannot be performed at once.
It often requires ten years or more to revolutionize an es-
tabhshed and profitable industry on any large scale. It
takes some years to prove the trustworthiness of the new
sorts and to convince the fruit-growers of the desirability
of the change. The production of a new variety is one great
step, but its introduction and distribution is another equally

177

178 PLANT-BREEDING

important one. The whole fruit-growing industry of
California amounts to an aggregate value of about sixty
milhons of dollars annually, and of this sum hardly one per
cent is represented by the varieties imported or created by
Burbank. If we compare these figures with those given foi
the importance of the Burbank potato, we find a great differ-
ence. But for a fair appreciation we must realize that the
Wickson plum is scarcely older than the ten years required
for its first wide distribution and that most of the other hy-
brids created by Burbank are much younger. We must
leave it to the future to decide what will be the real signifi-
cance of the improvements in fruits and flowers, of which
this one man has produced such an astonishing number of
excellences.

B. NEW VARIETIES OF FRUITS AND FLOWERS
Since the time of Darwin, the methods and achievements
of the breeders have played a large part among the argu-
ments adduced for the support of the doctrine of evolution.
In a broad sense they give us an insight into the processes by
which new forms are originated, and since the genera,l laws
of variabihty must be the same for the cultivated condition
and for the phenomena of nature at large, there can be no
doubt about the general validity of the argument. The ex-
perience of the breeders teaches that new forms from time to
time arise from the existing ones. It gives a general idea
concerning the affinity of the parent types to their offspring,
showing the similarity to be very large and the produced
differences correspondingly small. On the other hand it
shows that by the accumulation of small differences, wider
divergences may be obtained. This evidence led Darwin to
one of the main propositions of his theory of evolution, viz.,
that the larger groups in the vegetable Idngdomhave originat-
ed in the same way in which the smaller types are still seen

179

i8o PLANT-BREEDING

to come into existence. This proposition can be proved, and
in fact has been proved, independently of the question con-
cerning the details of that origin.

This broad principle of evolution by means of natural
laws having been established, the question naturally arose,
how far the breeder's experience could be considered as a re-
liable guide in evolutionary problems. On tliis point, how-
ever, many difhculties have arisen, all owing to the simple
fact that practical breeding and scientific experimenting are
things of altogether different purpose and method. Of late
it has been contended that the discussion of the scientific side
of the question should abstain from the use of the breeders'
results. There can be no doubt that in the end this will prove
the right way, since only then it will be possible to submit all
arguments to the most severe criticism.

At present, however, the purely scientific investigations
concerning variability and inheritance are only in their
beginning. Some fields have been more or less thoroughly
explored, and definite laws have been discovered. But the
more complicated cases are as yet hardly accessible to our
analysis, and the breeders' experience often covers so long a
series of years that the science of evolution is still quite inade-
quate to be compared with it. Moreover, the practical re-
sults contain so many indications and hints for the starting
of investigations, and so many details which otherwise could
easily be overlooked, that they are still contributing a most
valuable support to evolutionary science.

In estimating the value and reliabihty of the breeders'
work for theoretical discussions, its methods and aims should
clearly be understood. The practical work chiefly consists
in the selection of those specimens which are most suitable
for the purpose under consideration. But selection requires
material to choose from. This material, in some rare in-
stances, may be directly afforded by nature, but in the larger

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i82 PLANT-BREEDING

number of cases, it must be procured artificially. The pro-
duction and augmentation of variability is therefore to be
considered as a second point of almost equal importance to
the selection itself. It may be either plain and simple or
intricate. In the simple cases it is often possible to trace the
whole line of the work which has led to the ultimate result.
In the more intricate cases, however, the breeders ' purpose
is simply to increase the material for their selection as largely
as possible. All means conducive to this are combined and
the scientist finds himself at a loss in trying to discern the real
causes from amidst the chaos.

For tliis reason, I shall Hmit my present discussion to the
more clear and simple instances, leaving the complex cases
for my next chapter. Of course, a sharp hmit cannot be ex-
pected, and an arbitrary choice is unavoidable.

The investigations of the past decades have led to the rec-
ognition of various kinds of variability, and all further re-
search has to start from these distinctions. The breeders, on
the other hand, are not concerned with these divisions and
simply consider the variability of their plants as such. But
variability embraces on one side the existence of a larger or
lesser range of different types, and on the other hand the
actual transformation of one form into another. It is evident
that a scientist wishes to know in each case to which of these
two types an observed fact of variability belongs, while this
distinction may be indifferent to the practical man. In some
cases, however, it is not at all indifferent. I mean those im-
provements which have to produce races that can be multi-
pHed by seed. All the varieties of cereals, most of the other
agricultural crops, and many kinds of garden plants belong
to this group. Here it is manifest that only inheritable vari-
ations are of consequence, or strictly speaking, only those that
will be repeated by generations raised from seeds.

If, however, a new type is not intended to be reproduced

BURBANK'S HORTICULTURAL NOVELTIES 183

by seed, the available range of variability is much larger.
Such is, among the larger crops, the case of potatoes. More-
over it is the rule for fruit trees, which are multiphed by bud-
ding and grafting, and for all the garden plants which are
reproduced from bulbs, roots, layers, or cuttings. In these
cases, inheritance by seed has manifestly no significance at
all, and all kinds of variations, which would disappear or be
more or less reduced after sowing, here have the same value
as the strictly inheritable characters.

In other words, the range of variations is widened if the
selection is hmited to varieties with vegetative propagation,
and restricted when seed varieties have to be produced. It
is difficult to give an idea of the extent of this difference, but
it mav be stated here that the best estimates lead to the asser-
tion that for vegetative varieties selection finds a field thrice
as large as for seed varieties. Correspondingly, the amehora-
tions may be thrice as important and productive in the former
case as in the latter. Hence it is evident that whenever a
species can advantageously be multiphed in the vegetative
way, its artificial varieties will manifestly excel those of ordin-
ary seed plants.

The most simple case of producing new varieties is to
make use of ordinary fluctuating variabihty. By sowing on
a large scale, the extremes of this variabihty will easily be
obtained, and they wih surpass the average the more, the
larger the number of seedhngs examined. One or two of the
best individuals are chosen and the rest destroyed. The
chosen samples then become the origin of a new variety which
will remain constant as long as it is propagated only in the
vegetative way. As a first instance, I choose the loquat or
Japanese quince (Eryobothrya japonica). This species has
small yehow fruit of an acid taste, almost filled with the
large seed, which is covered with only a thin layer of fruit
flesh. But it has a pecuhar flavor found in no other fruit.

i84 PLANT-BREEDING

Of this species, Burbank has sown thousands of seeds and
cultivated the seedlings until they ripened their first fruits.
Among them he has chosen one excellent individual, which is
still growing on his farm near Sebastopol. It is a tree about
six feet high, with wide-spreading fruit-laden branches. Its
quinces have the same aroma as the ordinary loquat but are
much larger and of an orange yellow color. Their seeds are
not larger than those of the ordinary species, but the juicy
fruit flesh is greatly developed in thickness and very deli-
cious. These new Japanese quinces are considered as a
notable improvement, making one of the finest delicacies for
the table. In the same way, Burbank is trying to improve
the California currant (Ribes sanguineum). This species is
also known as the flowering currant of the Pacific coast and is
popular in European gardens as an ornamental spring-flower-
ing shrub. It flowers profusely but is poor in the ripening of
its fruits. In California it is abundantly found in the ^vild
state, and is often densely covered with racemes of small blue
berries. It occurs in quite a number of elementary types,
slightly differing according to their localities. Those of the
northern districts along the Pacific coast are notably hardier
in winter than the more southern varieties. In such cases,
selection has to begin with the choice of one or two of the ele-
mentary species, and Burbank preferred the hardiest, which
he secured from British Columbia. In sowing the seed of
this variety on a large scale, variations in the size and color of
the blossoms, in the number of flowers on the raceme, and
especially in the development of the fruit, soon appeared.
Among those he chose the best plants in dift'crent directions,
some having long clusters of bright blossoms, others distin-
guished by an increase of the pulp of the berries or an im-
provement in the flavor. Long rows of shrubs with an almost
inconceivable variety of fruits may now be seen on his farm.
Among these a definite choice must still be made and proba-

BURBANK'S HORTICULTURAL NOVELTIES 185

bly more than one variety will recommend itself sufficiently
for introduction into the market. Thus a new kind of currant
with a higher and more specific aroma will be added to the
already existing varieties. It is, however, Burbank's purpose
to submit these new selections to the process of hybridization
by crossing them with some other indigenous types, as, for
example, the glutinous variety found wild in the region of San
Francisco (Ribes sanguineum glutinosum).

Another wild CaUfornia fruit recommends itself for im-
provement. It is the Elseagnus, the pale yellow berries of
which are produced in such large numbers that the branches
are often seen bending under their weight. They are juicy
enough, but the taste is not that which is required to make it
a palatable fruit. Burbank has selected c[uite a number of
types and sown them on a large scale in order to gain a
marketable berry. By cultivation the plants have lost their
thorns, as in other instances, and the shape and vigor of the
whole shrub is notably improved. An increase in fertihty and
some amelioration of the taste has also already been obtained,
but a large number of highly variable plants are still awaiting
ultimate selection.

Freeing brambles of their thorns may seem to be an ar-
duous problem, but reducing the thorns to practical harmless-
ness is not at all difficult, for the prickles are variable in
number and size like any other character, and among many
thousands of plants some will be found very rich but others
very poor in these appendages. This character has the
great advantage of showing itself in early youth, and so the
choice may be made from among the young plants when still
in the seedhng boxes. All the prickly ones are rejected, and
only the smooth ones planted out. It is an astonishing sight
to see those long rows of harmless brambles awaiting further
selection at the time they ripen their berries.

The adduced instances may suffice to illustrate the prin-

i86 PLANT-BREEDING

ciple of selection resting simply on the ground of ordinary
or fluctuating variability. Its possibilities, however, are
limited, and since the breeder is always on the lookout to
widen the range of his material, it is but seldom that he is
content with this process of pure selection. In almost all
cases, he will try to increase the elements of his choice, and in
order to do this, he takes to the process of hybridization.

Hybridization, however, is not always a means of increas-
ing variability. In some instances hybrids are as constant
and uniform as their parent species even when propagated
from seed. A certain number of wild types formerly consid-
ered and described as pure species have since been proved to
be of hybrid origin, the types having been artificially produced
by repeating the assumed original cross. Kerner von Mari-
laun has described quite a number of such instances, and
Janczcwsky and others have produced hybrids which cannot
be distinguished from real species otherwise than by the his-
torical record of their birth. In such cases the breeder has
to be content if his hybrid proves to excel its parent species
in some industrial quahty, but without renewed crosses his
work is Hmited to its production and propagation.

Some such cases have occurred in Burbank's work also.
As an instance I will adduce the case of a bramble. A cross
has been made between the wild Californian dewberry
(Rubus Cahfornicus) and the Siberian raspberry, or Rubus
Sibiricus. The first is a small species of bramble and the
second closely allied to the common raspberry. But in both
the fruits are small and worthless. The hybrid, however,
surpasses both its parents in this important respect, having
large black berries, which are produced abundantly and
ripen several weeks eariier than both parents. As the
first notable improvement among brambles, it received the
name of primus-berry. Under this it has found its way into
the market. Other constant hybrids have since been pro-

BURBANK'S HORTICULTURAL NOVELTIES 187

duced in the same genus, among them the phenomenal
berry, which may be described as a gigantic red raspberry,
and which is now the most noted. It is a hybrid between
the CaHfornian wild dewberry and the Cuthbert raspberry.
All of them may be reproduced from seed as well as in the
ordinary vegetative way.

The increase of variabiHty which commonly is the aim
of hybridization may be induced along definite or indefinite
lines. In other words, the combination of characters which
is the chief aim of crossing, may be so simple as to be easily
calculated beforehand, or it may be so intricate as to pro-
duce a chaos of forms among which selection will ultimately
become the real factor of improvement. For scientific
purposes, the more simple cases are in many respects the
most interesting, and for this reason we shall now proceed
to the discussion of some of them. —

It is a much discussed question whether new characters
may be produced by crossing. Of course, there is no doubt
that new varieties and new races may originate in this way,
but this is not the same point. It is well known that the
larger number of hybrids simply owe their character to a
new combination of quaUties. It is the combination which
is new, not the quahties themselves. Some characters are
derived from one parent, others from the other. Each of
them may simply be inherited in the same way as in the case
of pure descent. But by their new combinations they yield
varieties of higher practical value, and notable examples are
afforded in those cases where one parent has contributed
vigor of growth, hardiness in winter, resistance to disease, or
productivity, and the other bright flowers, palatable fruit,
or nutritious seeds. For the breeder, such combinations of
characters have, of course, the same value as single favor-
able marks, but from a biological point of view the two prin-
ciples must be sharply distinguished. The combination of

i88 PLANT-BREEDING

characters produces nothing really new, and since this is
the ordinary case in horticultural crossing, the question
naturally arises whether, besides them, from time to time,
new elementary characters may arise by hybridization.

Burbank's experiments contain a number of cases in
which the appearance of actual novelty is quite striking.
Therefore I have discussed this question with him fully, and
the result is the conviction that the novelties in question are
only apparent, and that the real work of the breeder is not
the casual or accidental production of such, but a systematic
search for rare and as yet unnoticed, or perhaps, even for-
gotten qualities. It is based on his power to appreciate the
industrial value of characters which formerly had been
simply overlooked or considered of no promise in a commer-
cial direction.

Before considering Burbank's results in this line of facts,
a few other illustrative examples may be adduced. One
or two decades ago, a considerable number of varieties of
double- flowered lilacs had been produced by Lemoinc at
Nancy, France. All of them were hybrids, and as such
were very ornamental shrubs, with large clusters of bright
flowers, which excelled the older kinds by flowering during
a noticeably longer time. The double flowers, however,
were no result of the crossing but had been introduced as
such into the group of the ordinary varieties, by crossing
them with an old and forgotten double- flowered form, which
of itself was hardly ornamental on account of its small flowers.
It was the Syringa azurea plena, and the real source of
Lemoine's enormous success in this case was his idea of buy-
ing a tree of this variety and of starting a scries of crosses
with it.

Another instance is the seedless apple, which is now being
introduced into the trade as young grafted trees, which are
expected to exercise large influence on the whole culture of

BURBANK'S HORTICULTURAL NOVELTIES 189

apples as soon aa they are full grown, and shall have been
put upon the market. The character is nothing new. It
occurs in different varieties of apples and even of pears, but
it seems to have always been combined with some defect
which made the varieties useless, or at least, of inferior
quahty. Nobody seems to have suggested the idea of com-
bining with tliis quality the character of our best varieties,
and so our apples and pears are still in possession of the
cores and their seeds. What is new and promising for this
most important industry is the combination of this rare and
almost forgotten character with the qualities of a good and
marketable fruit.

One of the most interesting instances of this kind of
work on Burbank's farms is the wliite blackberry, a hybrid
race with abundant clusters of most delicious fruit of a per-
fect white. How can such a simple mark as the lack of the
black color evidently is, be produced by crossing? The
answer is very simple. Even as in Europe a white variety
of the raspberry from time to time occurs, so there is found
in the eastern states,- among the cultivated brambles, an
insignificant variety with small pale berries, x^s soon as
Burbank had discovered this fact, he secured some of these
pale yellow berries, introduced the type into his culture, and
crossed it with the variety called Lawton's blackberry. The
result was the combination of the white color with the excel-
lent qualities of the other parent. In a similar way, notable
qualities of rare or wild species have often been transferred
by crossing on cultivated varieties, thus giving rise to whole
groups of races of a new stamp.

Another instance is the stoneless prune, one of the most
celebrated marvels of the Sebastopol farm. Only one of its
varieties is ready for the trade, but the remainder are still
in a period of crossing and selection. A prolonged treatment
must still give them the same size, fleshiness, and flavor as

igo PLANT-BREEDING

other prunes have. The fruits we saw were of a clear blue
color and very attractive, though yet small. One may bite
completely through the middle of the prune, no stone being
met with. Inside of the plum is the seed, like an almond
in its shell, and with a fine taste like that of an almond, but
without any hard covering. It is surrounded only by a pale
jelly with some stray remnants of hard stony material,
which do not offer any resistance to the teeth or to the knife.

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Fig. 6o. The improved stoneless prune. The pit is not surrounded by
any stony material, but by a jelly.

All around the jelly is the clear, greenish, and juicy fruit
flesh, exactly as in an ordinary plum. The amount of stony
remnants varies greatly along with the other characters.
Some hybrids are more stony, others less. The latter will be
chosen, in order to be crossed with large, highly flavored
prunes, so as to obtain a superior c^uaHty, or they may be
crossed with all other existing cultivated varieties in order
to transmit the lack of a stone to all of them, and so ulti-
mately to replace all the present varieties by correspond-

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191

192 PLANT-BREEDING

ing stoneless ones, each of which will be appropriate for the
the same culture and use as one of the older types. Here,
once more, the cjuestion arose, can the disappearance of the
stone be the result of the hybridization of two or more ordi-
nary varieties ? Burbank's answer was a negative. He had
followed c^uite another way in procuring this astonishing
result. He had noted that about two centuries ago, in
France, a prune bore the name of "Prune sans noyau."
It was an indifferent variety, more a curiosity than a
thing of commercial value, since it produced only small
fruit. But Burbank at once reahzed all the possibihties
which this stoneless form offered. He was quite convinced
that it needed only to be crossed with the best ordinary
kinds to give a new and most attractive fruit. He pro-
cured seed of this long-forgotten French prototype and sowed
them on his farm. By their first fruits he satisfied himself
of the correctness of the description of them, and of their
fitness for his work. Of course, by one crossing, the chance
is not large enough to get a desirable combination. Repeated
crossings are required, and each has to be accompanied by a
selection of the most promising specimens. In this way,
size, flavor, and fleshiness may steadily increase, while the
amount of the remnants of the stone is always kept as small
as possible.

A counterpart to the stoneless prune, is the spineless
cactus. It belongs to the genus Opuntia, some species of
which are very celebrated, since they produce the Indian
figs, which may be seen in the markets of New York and
elsewhere in the eastern states, where, notwithstanding their
spines, they are highly appreciated as a dehcacy. The
Opuntias are desert plants, growing abundantly and in c^uite
a number of species on the plains of the semi-arid regions
of the West. Their stems consist of large flat pods, joined
together in the most fantastic manner. They are often seen

193

194 PLANT-BREEDING

reaching a height of some six feet, with numerous wide-
spread branches. Their fruit is relished by cattle, being
juicy and nutritious, and not too spiny. The disc-like seg-
ments of the stem also contain nutritious food, and this is
sometimes made use of, the prickles being softened by cook-
ing under the influence of the juice from the cellular tissues.
But cooking is an expensive mode of preparation, and thus
the thorns prevent the use and culture of the cacti on any
large scale.

From this discussion it is evident that a spineless edible
Opuntia would be a most welcome adcUtion to the agricul-
ture of the semi-arid West. It could be cultivated without
irrigation on the same plains where the spiny forms now
occur in the wild state. It would turn deserts into fertile
ranches, admitting of cattle raising, and thus restoring the
lands to human industry.

The genus Opuntia is very rich in species, many of which
are natives of Mexico. Here some kinds occur which have
no spines at all, and others in which these organs are only
partly developed. The spines of the Opuntia are of two
kinds, some being broader, smooth beneath their sharp tips,
and of a leafy nature; others are thin, covered all over their
length by little hooks, and more of the nature of prickles.
It is especially tliis latter kind which so often makes the
Indian figs, when not carefully peeled, disagreeable for eat-
ing. Burbank transplanted into his garden as many of these
deviating species as he could lay hands on, and began an
extensive series of crossings. Their aim was to combine
the absence of both forms of spines with the favorable qual-
ities of the tree-like kinds of the southern deserts. Of course
this could not be reached by a single cross, since numerous
qualities have to be considered before a really productive
thornless edible variety could be secured. Repeated crosses
and selections were required, but the result has ultimately

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195

196 PLANT-BREEDING

satisfied the highest initial expectations. Some large spec-
imens of spineless Opuntias may already be seen on his farm.
They are almost absolutely smooth, and Burbank deUghts
in softly rubbing his cheek along them, in order to give a
most striking proof of their complete harmlessness. He is
now propagating them, and numerous young plants may be
seen on his beds, which may some day become the starting
point for the desired new branch of desert agriculture.

Some of the hybrids of the stoneless prunes I have
quoted as still being in the possession of small remnants.of
the ancestral stone. So it is also with the spineless cacti.
Here and there a stray spine may be found on their stems,
but being allowed to search for them, I succeeded only in
securing a single one. If not absolutely absent, they are
at least, so very rare as to be practically innocuous. Of
course, years will be necessary to multiply the spineless cactus
so as to produce the enormous numbers required to replant
large parts of the present deserts. But while multipHcation
may be slow in the beginning, after some years it will go on
so rapidly that the practical result may not be so far off as it
now seems to be. Burbank gladly indulges in the prospects
which may then be reahzed, and it seems hardly possible to
overestimate the greatness of the benefit he will have con-
ferred upon mankind.

As another instance, the Shasta daisies may be cited.
On meadows, some large flowering kinds of daisies, or mar-
guerites, are often seen, covering the green carpet hke a fine
white cloth. They are as bright as many good garden flowers,
but on account of their commonness as wild plants, they
require some improvement before being capable of attract-
ing attention on introduction. They belong to the genus
Chrysanthemum, which includes the Japanese marigold and
other ornamental species. Burbank has introduced into his
farm cultures a Japanese species closely related to the mar-

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197

198 PLANT-BREEDING

guerites of the meadows, but surpassing them by the daz-
zHng whiteness of their flowers and some other striking quali-
ties. These he has crossed with the EngHsh daisy, which has
large flowers and stiff stems, and with the American daisy of
the New England states, which is tenacious of Hfe and hardy
of constitution, but not very white. By crossing these three,

Fig. 64. A flower-head of the fluted variety of the Shasta Daisy.

he has brought about a wondrous degree of variability,
ranging from small, button-like flowers to others of the size
of a hat. Selection thus being made possible in different
directions, Burbank chose that of increasing the size, com-
bining with it other valuable quaUties. The tall, stiff stem
of the Enghsh species, the bold white flowers of the Japan-

BURBANK'S HORTICULTURAL NOVELTIES 199

ese form, and the abundant bloom of the American sister
have given the basis of the combination. After this, selection
was made for size and shape and superior whiteness, and a
variety was produced in which the green tufts of foUage were
covered during a large part of the spring and the summer
with crowded, bright white blossoms. This new and, on
account of its easy propagation, cheap garden flower received
the name of Shasta daisy, after the snowy mountain of that
name in northern Cahfornia.

The European marguerites are well known for their
high degree of variabihty, and they have transmitted it to
their hybrid progeny. In combination with the characters
derived from the other parents, this fact opens the possibihty
of producing a considerable number of secondary types.
One of them excels by nicely cup-shaped flower heads,
another by tubular ray-florets. Some show a tendency to
become double, and in others, valuable, or at least curious
marks, are still awaiting selection. Long rows of these
bright blossoms were in full bloom at the time of my visit,
and many of them were marked by httlc ribbons in order to
save their seed separately afterwards.

The Heuchera may be cited as a parallel with the Shasta
daisy, though their culture is only in its beginning. The
garden species of this genus, Heuchera sanguinea, has long
but slight spikes of small bright flowers of a blood red color.
It is not a very striking plant, making beautiful tufts only by
very successful culture. It affords a promising material for
amelioration, but unfortunately, its wild congeners are very
inconspicuous plants with pale greenish or small wliite
flowers. Burbank, however, discovered, on one of his ex-
cursions through the Cahfornian forests, a local variety of
the common Heuchera micrantha. This is a nice little
plant, growing abundantly along the rivulets in the woods.
He found a plant with crisped leaves and decided to combine

200 PLANT-BREEDING

this most beautiful form of the foliage with the red blossoms
of the garden species. He transferred the plant to his garden,
crossed it, and, at the time of my first visit, had thousands of
young seedhngs, among which he selected those which, by
the curled form and brownish color of their first leaves,
already indicated the success of his combination.

In the same way, Burbank has tried to improve garden
plants by the introduction of some new type and by working
it "into the strain" as the phrase goes. As a last instance
his ameHoration of the garden Canna may be quoted. Every-
where in our gardens we may now admire, besides the old
species and hybrids of Canna, which are still cultivated for
their large and beautiful fohage, the newer varieties of so-
called flowering Cannas. Their fohage is relatively low
but crowned with large clusters of red and yellow flowers.
They occur in two types, the French type or that of Crozy,
and the Itahan type with its orchid-shaped flowers. Bur-
bank has improved these by the combination of their quah-
ties with those of a native American species, Canna flaccida.
Thus resulted the Burbank Canna, which soon found its
way into the gardens on account of its giant, orchid-like
flowers. Its upper petals measure fully seven inches across
and are of a rich canary yellow with carmine spots. A
second hybrid of the same origin was the Tarrytown Canna,
notable for the great abundance and richness in color of its
flower spikes.

Many other instances could be adduced, since it is Bur-
bank's custom to extend his experiments over as many
species as he can possibly bring together in promising
varieties or speciniens. Unfortunately, the evidence which
is necessary to insure scientific value to the practical ex-
periments is not always easily obtained. From a practical
point of view, there is no reason for pubUshing it, and when
it is given in catalogues or references, tliis is often done for

20I

202 PLANT-BREEDING

the purpose of illustration only. The fruit-grower and the
amateur cultivator of garden plants are quite satisfied with
the visible quahties of their new varieties, and the question
as to their origin has, as a rule, but small interest for them.
It is to the personal kindness of Burbank that I am indebted
for most of the details concerning the scientific side of his
cultures, and, of course, my visits were too short to touch
upon all the questions exciting a similar interest.

It seems to me a fact of high scientific significance that
combinations of characters can be obtained by crosses in
almost all the arbitrarily chosen directions or degrees, but
that new character-units are either never produced or at
least so rarely that an artificial origin is hardly beyond legiti-
mate doubt. Concerning the combinations of characters,
the investigators of the last decade have discovered dis-
tinct laws which, however, in large part, are related to
varietal marks. Real specific differences must, of course,
also obey distinct laws in their combinations, and the in-
variability of some of Burbank's hybrids, as for example the
primus-berry, shows these laws to be more narrowly cir-
cumscribed than is usually assumed.

C. HYBRIDIZATION AND SELECTION
Apart from the clear and simple cases we have dealt with
in our last lecture, the ordinary aim of the hybridizer is to
upset the constancy of his plants, and to bring them into a
state of unstable equilibrium which in the end will result in
an extreme chaos of forms. From this chaos, he makes
his selections, and if they do not at once comply with his
wishes, he continues liis crossings in order to widen still
more his range of types. In doing so, he is careless about the
real source of the improvements he obtains. He knows
the origin of his groups and strains, but rarely that of their
single constituents. Or, to put it into a simple phrase, if

BURBANK'S HORTICULTURAL NOVELTIES 203

his hybrid family is the result of the crosses of six or eight
or perhaps more original species, he does not care whether a
given individual of that family has all those parents in its
ancestry or only a few of them. The visible features of
the individual hybrid often point to an origin from definite
parents among the group. It may have the foliage of one
form, the branching of another, and these combined with
the flowers or fruits or the productiveness of two or more
others. Its pedigree may thus be guessed at, and for ah
practical purposes this is quite suthcient. But in most of
these cases a scientific treatment is excluded, since exactly
that which we should want to prove, is simply assumed on
the ground of relatively loose probabihties.

What the breeder is very careful about is the choice of
the starting points for his work. Species, elementary species,
varieties, individual excellences, have to be tested with the
utmost care before being aUowed an introduction into the
strain. For the crossing with indifferent types would in-
crease the work without affording any real chance of pro-
gress, and species possessed of some undesirable character
might, of course, transmit this to the hybrids, as well as
any favorable quahty. They must be excluded at the out-
set, and this requisite is of so essential a nature that it may
be said that half of the ultimate result depends upon the
initial choice and only the other half on the success of the
ensuing hybridizations.

This rule is often stated by saying that half the battle is
won by the first selection. From it we may deduce a con-
firmation of our conclusion in the last chapter, viz., that the
results of hybridizations consist in the combinations of
given characters, and not in the accidental production of
new ones. All depends upon what is already present,
since simply the new grouping is the source of the almost
inexhaustible variabihty.

204 PLANT-BREEDING

On the farm at Sebastopol I saw long rows of Calla, all
richly flowering and showing an astonishing amount of
variability. High and dwarf forms and all their intermed-
iates, large and small cups, varying from white to yellow
and not rarely spotted, leaves of all forms and color, some
hairy and some smooth, some of a dark green and others
spotted or even striped with white, more or less purple and
brown, and with many other differences, too many to be here
summarized. Add to this various degrees of hardiness and
frost resistance, a prolonged period of blooming, rapid
propagation by means of side shoots, and other (qualities
that may cause the varieties to become some day quite
ordinary garden plants and you may have some idea of the
almost inexhaustible range of variability. If we now ask
whence this large group of characteristics comes, the answer
is readily given by the history of the culture, but whenever
we ask for the ancestry of one single striking plant, it is
not historically known, but must be derived from its apparent
affinity to some among the ancestors of the whole family.

Burbank began his work on the Calla with the ordinary
cultivated species, which is almost everywhere known under
its names of Calla athiopica or Richardia africana. He
secured the commercial varieties, including some dwarfs and
some spotted forms, hybrids whose parentage seems to have
been forgotten. From their crosses he secured a fragrant
variety with a pleasing perfume. It is of a semi-dwarf
stature and is one of the most freely-blooming kinds within
the old range of forms. Under the name of "Fragrance"
it has found general recognition, especially among eastern
florists. The range of possibihties in this group was, how-
ever, very hmited and seemed in the main to be exhausted.
Therefore, Burbank decided to widen it by the introduction
of new species. Here one of the most striking features of
his method may be observed. If we consult the history of

Fig. 67. The tiny, perfectly formed Calla, by the side of the one of nor-
mal size, has been bred downward to show how plants may be reduced
as well as enlarged in size. The small one is less than an inch and a half
across.

205

2o6 PLANT-BREEDING

the most famous among the older species of garden flowers
and their hybridizations, as for example the Begonia, the
AmarylHs, the Gladiolus, and many others, we find that
progress has, in the main, been slow, advancing only by
more or less accidental leaps. These advances were the
result of the discovery or introduction of new promising
species and of their being worked into the strain. They
often mark distinct periods in the progress of these hybrid
famines, and not rarely they have been achieved by different
breeders. In such cases, the history of the whole strain
may be mere or less easily traced. Opposed to these suc-
cessive introductions of new species into a hybrid family,
is Burbank's principle to start at the very outset with as
many promising species as possible, in fact with all that may
be available in any nursery or botanical garden, or may be
collected in their native haunts in any part of the world.
The Callas give a beautiful instance of this method, five
new types having been added at once to the original stock.
Of course, each of them has brought its pecuHar character
of flowers, foHage, and mode of growth, and an almost endless
range of combinations must be the result. Calla hastata is
a yellow species from the Congo; ElHottiana is of a still
richer and darker yellow and has spotted leaves; Pentlandi
is yellow with a dark purple spot; Rehmanni is pink on
the outside and rose purple with a crimson spot witliin;
Nelsoni is small, pale yellow and purple. All these new
types have been variously crossed among themselves and
with the old white kinds. Of course, the crosses were made
partly with definite combinations in view, and partly as
occasions were offered, and the seeds of the crosses were
saved and sown in mixtures. Each single hybrid of the next
generation manifestly had only two parents and thus a second
and even a third season of crossing were required to obtain
combinations of a higher rank. Thus the range of varia-

BURBANK'S HORTICULTURAL NOVELTIES 207

bility has steadily been increasing, and it may be doubted
whether it had already developed all of its possibilities at
the time of my visits. Some of the forms have been put
upon the market, as for example the "Lemon Giant" which
is said to be a cross of the albo-maculata and the hastata.
Others arc still awaiting selection and recrossing, but are
already showing combinations and extremes of character
which are new to the family. Among them bulbs of ten
inches across and eight pounds in weight, with leaves of
proportionate size and vigor, may be mentioned. Each
year the finest flowers and the easiest-growing plants are
selected for the new crosses, in order to exclude all combina-
tions that would not contribute, in the end, to the main
purpose, \dz., the production of rich garden plants of easy
cultivation and rapid propagation.

The same aim is pursued in the case of most of his other
attempts to improve flowering plants. The size and richness
of colors and designs of the European hybrids of Amaryllis
can hardly be improved, but they are greenhouse plants,
requiring a number of years for their development and are
slow in their propagation. In the beautiful chmate of Cal-
ifornia, they may, however, become changed into garden
plants by first cultivating the best commercial hybrids in a
greenhouse, and placing their pollen upon the ordinary,
almost unimproved varieties of the garden. By sowing the
crossed seed in the garden, the weakest and most unHkely
specimens are soon excluded, and only those remain for
repeated crossing which have inherited a sufficient degree
of resistance. Then Burbank worked for more abundant
bloom, more flowers to the scape, and more scapes from the
bulb, an earher and more lasting blooming period, and lastly,
for a more rapid multipHcation in the vegetative way. I
inspected a bed of fine bulbs of Amaryllis on the farm near
his house. Some of them had almost no side bulbs at all ;

2o8 PLANT-BREEDING

others had produced some ten or twelve during the summer,
and in the extreme instances this number amounted to 20 to 24
young bulbs on one plant. These were marked for selection,
and their seed pods gave proof that they had already been
crossed with others, in order to combine their abundant and
easy propagation with the fmest and most showy flowers.

Similar results were arrived at with the Gladiolus, of
which, however, hardy garden varieties had already been
secured in Europe. But the stems were too weak, the flowers
too distant, the petals too narrow, and all those deficiencies
had to be eUminated by crossing with suitable parents. Some
new species were introduced from South Africa, and during
ten years, about a milHon hybrid seedHngs were raised.
Among these quite a number of new forms have been chosen,
being hardy plants for the open air with stiff culms and
densely crowded spikes of large bright flowers.

Experiments of this kind have been quite numerous.
Some are of older date and had already been concluded before
the time of my visits. Others were of more recent date and
some only in their beginning. From the long list of species
treated in this way, a few may be chosen to give a stifl better
idea of the methods followed. One of his most notable
achievements is the amelioration of the wild CaHfornia tiger
lily, Lihum pardaHnum. This is a species which grows
abundantly in many of the redwood reserves of California,
bearing its large curled flowers of a fiery red on stems four
or five feet high. It is remarkable for being very rich in
sub-species and varieties, and almost every locaHty where it
grows is said to have its own type. Burbank collected as
many of them as he could, and crossed them with the culti-
vated species and hybrids of our gardens. Hundreds of
thousands of crossed seeds were produced and the bulbs
grown from them showed a diversity of blooms and colors
greatly exceeding that of the previous stock. Repeated

BURBANK'S HORllCULTURAL NOVELTIES 209

crosses had to be made, and the ultimate result was the
combination of the best features of the older garden lilies
with the typical form of the California species. Many of
the known Hlies of the world have brought their peculiari-
ties for the enrichment of the native form, and from half a
million bulbs some few were in the end selected as the most
promising and were given to the trade. All the remainder
of the bulbs were burned, with their stems and flowers, in
a great bonfire.

The clematis has produced a hybrid with bell- shaped
flowers of beautiful colors. The columbines have resulted
in a variety without spurs. The Cahfornian poppies, which
are highly variable as a wild species, have been asked to widen
the range of their flower colors, embracing orange, white and
purple, and almost all intermediate shades. Common pop-
pies (Papaver Rhoeas and allies) have produced not only red
and white, striped and spotted varieties, but also a new one
of a pale purplish blue, which, in itself, was a ciuite insig-
nificant flower, but full of promise of breaking up the exist-
ing range of colors and giving, by continued crosses, new
combinations and new shades outside of what is already
known in this group. The scented tobacco with its large
white flowers, which open in the evening, has been crossed
with the Mexican Nicotiana glauca, a vigorous shrub with
huge clusters of flowers, which, however, are of a pale green
color. The combination had in \dew the production of a
perennial and richly blooming variety with the odor and
the bright flowers of the afiinis parent.

One of the most notably difficult crosses is that of the
common opium poppy with other species of the same genus.
Ordinarily the crosses are infertile, and success is thereby
excluded. Burbank tried to cross it with the Papaver ori-
entale, a perennial garden plant with very large and showy
flowers of a fiery orange red. Like the opium poppy it is

2IO PLANT-BREEDING

extremely rich in garden varieties and thus affords excellent
material for hybridizations. The affinity between the two
species is very small and the crosses have only succeeded in
one direction. The oriental species does not accept the
pollen of the somniferum even if it is placed upon its stigma,
but remains wholly sterile under its influence. The recipro-
cal cross in which the oriental is the pollen parent, produces
some few seeds, but from these hybrids arise with a remark-
able degree of variabihty in their fohagc and flowers. The
hybrids themselves arc also almost sterile, some producing
no flowers at ah; others only small ovaries or miscarried
ones reduced to a sharp point on the top of the flower stalk.
They can, however, be fertilized with the pollen of the opium
poppy, and by doing so a second generation of hybrids has
been produced. This generation grew by the side of the
first one on a bed of Burbank's home farm, when I visited
him, and was seen to be extremely variable in its fohage
and in its manner of growth, whether annual or perennial.
Each individual was typical, having all of its leaves of the
same shape, color, and hairiness, but among them hardly
any two were aHkc. Selection must still be made, and the
selected individuals must be crossed again in order to secure
still more beautiful garden flowers.

I am now coming to the description of the most celebrated
of all Burbank's crossings, those of the plums. In a large
portion of the southern states, where the European varieties
of plums had yielded only failures, notwithstanding long and
careful attempts, the new hybrids are claimed to make plum-
growing possible. In many parts of CaHfornia plum culture
is said to become more profitable by the introduction of some
of Burbank's hybrids, and a new epoch of fruit-tree growing
has thereby been opened. Hardiness and productiveness
are the main features by which these results have been
secured, and they themselves were obtained by the combina-

BURBANK'S HORTICULTURAL NOVELTIES 211

tion of the characters of Japanese and native American
species, with the flavor and fleshiness of the older cultivated
sorts. Some of his best hybrid and introduced varieties may
be named and briefly described, according to the claims of
their originator. "Abundance" and "Burbank" may thrive
almost everywhere. They arc capable of resisting frost
during the period of blossoming. The "Burbank" is said
to supplant the older varieties over large regions and may
even be cultivated in districts where plum culture was for-
merly impossible. It has been exported to South Africa,
AustraUa, and New Zealand, and many thousands have been
planted in these distant countries. It has proved to be the
most reliable plum, as well for household purposes as for
canning and shipping. "Sweet Brotan" is another success-
ful hybrid, and "Satsuma," an introduced variety miscarries
in some districts, but yields a large harvest in others. About
twelve years ago, the giant prune was introduced. Others
are younger, and almost every year some new ones are placed
on the market. Their total number now exceeds a dozen.
Of the youngest varieties the fruits are not yet on the market,
and only cuttings or young trees are for sale. In some cases
companies have been organized with the aim of propagating
and multiplying one of Burbank's hybrids, in order to dis-
tribute thousands of trees at the first moment of introduction
to the public. The Maynard plum may be cited as an
instance.

Ordinarily, Burbank sells the whole variety and leaves
the propagation and sale to other men. The result is, that
of his previous hybrids, nothing is now to be seen on his
farm. The visitor sees hundreds of trees, each grafted with
from twenty to forty or often more hybrids, all of which are
awaiting trial and selection. Here the prunes of the future
are growing, but of course they are rare instances among
the thousands of good and palatable fruits that will have to

212 PLANT-BREEDING

be rejected. The casual inspector cannot discern them, and
moreover he is simply bewildered by the profusion of lus-
cious fruits which are tempting his eyes and palate on all
sides.

Among the American species of the large plum genus, the
beach plum or Prunus maritima plays a prominent part in
Burbank's crossings on account of the small demands it makes
on soil and water. It is one of the most common shrubs
along the eastern shores, growing everywhere on the coast
or along the larger rivers, in dense bushes. It is very pro-
ductive and is satisfied with almost any life conditions. It
thrives as abundantly on dry and sandy plains as where the
soil is covered by salt or fresh water during part of the year.
Tt abounds in varieties having red or blue or yellow prunes, .
sometimes large and sometimes small, ripening early in some
locaHties and late in others, affording thereby a rich material
for selection and hybridization. The prunes are often as
small as huckleberries and are gathered onl\' for preserving
purposes, but it blooms a month after most of the other
species and is thereby almost free from the danger of having
its blossoms destroyed by frost while it proceeds with the
ripening of its fruit until late in the fall.

All these notable quahties Burbank has tried to transmit
to his hybrids, combining them with the usual requirements
of palatable plums. By successive crosses and correspond-
ing selections, the bush form of the beach plum has been
eliminated from the hybrid strains, upright trees having
been preferred for the further crosses. Stones as small as
those of the cherry, in plums of full size are another result
of these combinations. The first generation of the original
crosses were, of course, only of relative value, but by re-
crossing them with as manv varieties and hvbrids as were
available, an extremely rich material for selection has been
secured.

BURBANK'S HORTICULTURAL NOVELTIES 213

In some cases, the history of the succeeding crosses may
still be traced, although of course the selection has steadily
eliminated some characters and augmented others. But
wherever the pedigree is historically known, the explanation
of the different characters of a hybrid and their reduction
to those of the single parental types is, of course, more rehablc
than in the ordinary cases. As an illustration, Burbank has
described the pedigree of his Alhambra plum. It is a com-
bination of seven distinct parents, some of which arc of
American, some of Japanese and others of European origin.
Among the latter some are probably the offspring of old and
long- forgotten crosses, thus making the pedigree still more
compHcated. Each generation requires about three years,
the seedlings being grafted in their first summer on old trees
and thereby being brought to blossom at a very. early period
of their life. The whole pedigree includes, by this manage-
ment, only tliirteen years. The initial cross was made
between the Kelsey plum and Prunus Pissardi, an ornamen-
tal tree with a dark purpHsh foliage but without edible fruit.
The offspring of tliis cross was fertilized with the pollen of
the flowers of the French prune, and the threefold hybrid
thus improved was destined for still further combinations.
For these, in the meantime, hybrids had been prepared in
order to bring the desirable characters of two new forms into
the strain by means of a single cross. First a hybrid of
Simoni and triflora was used, and the offspring obtained
in this way was fertilized with the pollen of Americana x
nigra, bringing up the total number of the constituents
to seven. Of course, the offspring of this last cross was
utterly variable and among it the Alhambra was chosen as
the best.

Summing up the main lines of this historical sketch, we
may put them into the following pedigree:

214 PLANT-BREEDING

Kelsev ...... x Pissardi

a ..... X French prune

I

Simoni x triflora x b

I

c X Americana x nigra

Alhambra.

It seems hardly necessary to point out that the Alhambra
has neither been the only result of this pedigree nor that the
crosses in its ancestral line have been the only ones performed.
Quite on the contrary, tliis pedigree is only to be considered
as one of the hundred or perhaps thousands of diverging
lines by which the main types and their numerous subordinate
varieties have been combined with one another. The re-
sult has been an utter chaos of mainly excellent lands of
prunes such as it was at the time of my visits. Of some of
them the pedigree could be traced, but there were many of
doubtful superiority, for which it would not be worth while
to keep the historical record.

The selection, of course, must be performed chiefly dur-
ing the few summer weeks when the branches of the grafted
trees are loaded with ripe fruits. It is a most curious sight
to see on one and the same tree, branches with foUagc of
different colors and forms, some growing slowly and some
already covered with side branches and bearing red, yellow
or blue, flat and round, small and large, ripe and unripe,
sometimes only half-developed fruits. The total result is
strikingly bizarre. When the fruit is ripe, Burbank walks
along the rows of trees, marking those which are either
decidedly best or useless as far as can be judged by first
examination. Then his foreman removes all those which
have been marked as valueless, leaving only about half of
the stock and making space for new seedHngs to be grafted

Fig. 68. A. The plum. B. The brown-leaved Prunus Pissardi, two species

grafted on the same tree.

215

2i6 PLANT-BREEDING

on the old branches. x\fterward, the remaining fruiting
branches receive careful investigation. Their number
reaches many hundreds each year, the total sum of all his
hybrids amounting to some three hundred thousand, and
having afforded the selection material for nearly twenty
seasons. The comparison, of course, is based, in the first
place, on the inspection of those hybrids that are ripening
their fruit at the same time. But the best types of previous
years must be used as standards in the work, most of them
bearing fruit for a second or third time, and thus facilitating
the comparison. Finally some four or five are selected as
being ready for the trade, and these arc then multiplied as
rapidly as possible and offered for sale.

The remainder, after the extirpation of all minor forms,
yields a harvest of hybrid seeds for the next sowing, and are
themselves destined for renewed crosses in the following
year.

In his selections, Burbank is guided by a special gift of
judgment. By virtue of his long study of plums and by
the comparison of so many thousands of varieties of them,
he has acquired a rare and comprehensive knowledge of
all their qualities, which enables him to tell on his farm,
which kinds are the best for shipping, wliich for canning
purposes, which will be household fruits, and which good for
drying. He knows his trees, observes their behavior during
the winter, pays attention to the vigor of their growth and
the mode of their development, and from the inspection of
all these qualities, can distinguish the hardy varieties from
the unresistant ones, and predict for each the region and the
life conditions under whicn it will probably thrive. To a
large degree his choice is guided by such considerations,
and anyone who has a lesser experience in the selection of
prunes can hardly understand how it is at all possible to
choose the right kinds for their distinct uses, but the success

BURBANK'S HORTICULTURAL NOVELTIES 217

which his creations arc said to have had in the United States,
and even in many countries of the old world, is the best
proof of the reliabihty of his judgment.

This judgment is due partly to his genius and partly to
his broad experience in all cjuestions of practical plant breed-
ing. But its appHcation to a definite group of hybrids rests
chiefly on the study of that group itself. His experience
with plums will enable him to make faster progress in the
study of hybrids of any other genus, but it is of no direct
avail for the practical work with them. More than once in
our discussions, Burbank has laid stress on tliis point, assert-
ing that each new family has to be studied anew, and given
the same care and devotion, in order to learn all about its
cjuahties and possibilities. There are, of course, some general
rules, but the ultimate result is mainly dependent upon a
thorough knowledge of all the characters which may have or
may afterward gain some influence in directing selection.

All these considerations are, however, related to the work
of crossing and selecting, which, as we have seen, is only
the second part of the whole study. The first part, insuring
half of the result, is the primary choice of the varieties to
start from. These have to include as many profitable
quaUties as are at the time available, but this part of the
work is manifestly to be continued along with the crossing.
He must be constantly on the lookout for new types, and
whenever attention is directed to newly- discovered species,
or when the study of the strains points to desirable quahties
which may be secured by the use of older native forms
which have not been tried until that time, new introductions
must be made. By increasing the number of the parent
species, and thereby that of the available characters, the
range of variability is considerably widened, and numerous
possibiUties of new combinations are opened. From this
point of view, I now mention the introduction of the cherries

2i8 PLANT-BREEDING

and the apricots into the hybrid plum families. The cross
between the cherry and the pkim was readily made, and the
hybrids were abundantly fertile. A new element was in-
troduced by two evergreen cherries, one of the Pacific coast
and one from Mexico. These were easily crossed, both
with deciduous cherries and with plums, but the results are
still awaiting selection and improvement.

The hybrids of the plums and apricots arc called by
Burbank plumcots, and a certain number of these most
dehcious and beautiful fruits I have seen on his farm at
Sebastopol. They have the outer appearance of apricots
but combine the rich and varied colors of the prunes with
the soft indument of the former. Dark blue and downy
apricots are as striking a novelty to the eye as the combina-
tion of the flavor of prunes and apricots in one fruit is flat-
tering to the taste. Some had a yellow fruit flesh, in others
it was red or pink or nearly white. The dark red varieties
seemed to me the most juicy, and were, perhaps, to be the
next to be definitely selected. Some phimcots have free
stones, but others were cling stones. In many other respects,
striking differences were observed, giving an almost com-
plete material for his selections.

It is difficult to tell whether the range of possibilities of
the crossings of plums has reached its ultimate limits or
whether it will afterward assume still more astonishing
aspects. The cross between apricots and the Japanese
plum has been attended with difficulty, and has succeeded
only by the use of distinct varieties. Peaches should next
come up for trial, but their crosses with plums have been
devoid of success until now. But perhaps some of the hy-
brid strains may be more suitable than others, and new
attempts may succeed where older ones have miscarried.
In case of success in this jiew hne, the range of possibilities
will become almost inexhaustible.

BURBANK'S HORTICULTURAL NOVELTIES 219

Leaving our sketch of the historical evidence given by
Burbank concerning his hybrids, some points of biological
interest remain to be mentioned. In the first place, crosses
are by no means always successful. The result depends
mainly upon the affinity of the chosen parents. Whenever
their systematic differences are too great, the cross will be
infertile, or at least the produced hybrids will refuse fertil-
ization, even with the pollen of their parents. Repeated
crosses are impossible and no practical results can be ob-
tained. Or all the hybrids may be of inferior quaUty, not
promising any improvement and thus are not worthy of
further culture. Of this, Burbank gives an instance in an
experiment with a Cahfornian dewberry. He transplanted
a specimen of this indigenous species into his garden, isolated
it, and brought to its blossoms the pollen of almost all its
alhes he had at that time under cukivation. He gave it
the pollen of brambles and raspberries, of strawberries and
roses and even of cherries, apples, and pears. All the seed
was saved in a mixture and a strange lot of hybrids arose
from them the next spring. Some repeated well known
types, but many seemed full of promise of new forms. At
the blooming period, many defauUed, making no flowers at
all, and the remainder proved to be utterly sterile; no single
hybrid could be chosen by which a new strain could be
obtained.

A parallel instance is that of the Nicotunia. This is
Burbank's name for a hybrid he once won between a tobacco
plant and a Petunia. The parents are so distant that, as a
rule, the cross never resuUs in good seeds. Among hundreds
of seedless capsules, he found one in a better condition, and
from its contents raised one single plant. This, however,
was an annual and absolutely sterile and so the experiment
ended with its death.

A last point wMch we have to discuss is the interest

2 20 PLANT-BREEDING

attached by the practical breeder to the purity of his fer-
tiUzations. Of course, in scientific investigations, the father
is of equal importance with the mother, and the utmost care
has to be taken that the stigma is covered with pure pollen.
Moreover, in the pedigree, the hnes of the male ancestors
require the same care as the female line. Exact and elaborate
book-keeping is the rule, and no single polHnation should
be made that is not thoroughly controlled and registered.

In practice, however, such a susceptibility would be as
impossible as useless. The proof of the pecHgree is not the
aim of the experimenter. He only looks for the result. In
crossing six or seven species and hundreds of their hybrids,
the pollen is brought from one flower to the other, as oppor-
tunity is offered. Hundreds of crossings may be made in a
few hours, and their seed may be saved in mixture without
special care, or too much loss of time. If, however, each of
these crosses has to be kept separate, to be labeled and
registered, and its seed sown apart from the others, the
amount of work will increase a hundred-fold without any
chance of giving more or more profitable hybrids.

Separate pedigree book-keeping being thus impossible,
small impurities of the pollen cannot be avoided and are not
to be noticed. Pollen is brought by the finger to the stigma,
but a breeder would simply laugh at the idea of a scientific
investigator washing his hands between successive polhna-
tions, or inspecting his fingers with a lens in order to remove
some stray remaining pollen grains Quite on the contrary,
such unintentional crosses often bring greater chances of
unexpected success than the regular and contemplated pollin-
ations, and if, perchance, they give hybrids of inferior quahty,
the damage is only small, since the offspring is sure to be
eliminated bv the next selection. Thus we see that some
freedom must be allowed in the choice and in the purity of
the pollen. But, on the other hand, it is easily seen that much

BURBANK'S HORTICULTURAL NOVELTIES 221

caution is to be observed in the scientific interpretation of the
breeder's results.

As a general rule, we may state that the broad hues of
practical hybridizing and selection afford highly valuable
resources for theoretical discussions, but that on single
points they should not be accepted as definite proofs, but
only as indications for more sharply circumscribed experi-
ments. Even with this restriction, however, the value of
Burbank's work for the doctrine of evolution, compels our
highest admiration.

D. I^IUTATIONS IN HORTICULTURE
For the larger number of horticultural varieties we do
not know the origin. jNIany of them are older than the his-
torical records, others have been found in the wild state or
in foreign countries or in old-fashioned gardens. A certain
number appeared in nurseries and cultures, but their first
generations were overlooked and they were appreciated only
when it was already too late to study their first appearance.
Whenever this first appearance has been noted and re-
corded the development of the variety took one or two or a
small number of years. Sometimes it appeared with the
full chsplay of its quahties and proved constant from seed
from the very beginning. But such cases are rare. Ordi-
narily it was discovered, at first, in a very imperfect and often
scarcely perceptible degree of development, or it was not
constant from seed. In both cases it had to be developed
by selection in order to insure a normal degree of purity and
constancy. This process requires some years, and their
number is different for different species, according to their
capacity for self-fertilization, their fertility, and other factors.
Whenever the varietal mark is plain in the first year,
selection has only to produce constancy. Tliis might be
attained at once, if the visits of insects could be excluded,

222 PLANT-BREEDING

either by isolation or by covering the flowers and fertilizing
them artificially. If this is done, the varieties prove con-
stant, with few exceptions. In practice, however, isolation
and artificial fecundation are often too cumbersome, and the
easier way by repeated selection is preferred. Gradually
it eUminates the effects of the natural crosses with the neigh-
boring varieties and in three to five years it ordinarily brings
the purity up to the degree required for commercial purposes.

If, however, the varietal mark should show itself only
imperfectly in the beginning, being Hmited to a supernum-
erary petal, to a slight indication of a new color, to a fine
line of a different hue, or to a hardly perceptible fragrance,
selection has to improve it. In the case of pure and artifi-
cial polHnation the orcUnary variabihty of the new mark
would bring it to its main condition as soon as the sowings
reach the required extent, but in practice the process must
be combined with the described gradual elimination of the
effects of crosses, by which it is, of course, made much
slower. Four to five years, however, are, as a rule, sufficient
to reach the aim.

The way in which all these varieties originate is best ex-
pressed by the technical term of chance seedlings. Fruit-
growers, nurserymen, and amateurs are always on the look-
out for such. Even among the commercial growers there is
a regular search for deviations in the direction of improve-
ment. Any seedling that chances to show more desirable
characters than the average will be noted and cared for. To
this discriminating search is due the superiority of some of
the leading varieties of fruit-trees, which have been recog-
nized as meeting special requirements and have been multi-
pUed accordingly. Such chance seedlings occur every-
where, from time to time, but the cause of their appearance
is, as yet, wholly unknown. The only thing we know about
them is that among large numbers the chance of finding

BURBANK'S HORTICULTURAL NOVELTIES 223

them is greater than in small cultures. In small private
gardens they are very rare, but in large nurseries they will
hardly ever fail, although they may often be much rarer than,
for example, one in a year.

Hybridizing being one of the most important proce-
dures in many of the larger nurseries, the c|uestion has often
been raised whether such chance seedhngs should be more
frequent, or rarer, after crossing than in pure strains. Of
course, this question is of the highest practical as well as
scientific interest, because if it had to be answered in the
affirmative, at least one possible cause would be indicated.
It seems quite possible that such should be the case, and
even our knowledge concerning the numerical laws of the
splitting of a hybrid progeny does not exclude the possibihty
that among a thousand and more offspring some chance
deviation may occur. As yet, however, the evidence at
hand is too rare to justify a definite conclusion.

In this respect the same conditions prevail on Burbank's
farms as everywhere else. Of course, sports occur quite
often and, in many cases, may even be produced at will. But
sports include a wider range of variability than the chance
seedhngs. The latter can always be considered as sports,
but not all sports belong to this same group. A critical
review of some of the most interesting sports among the cul-
tures of Santa Rosa and Sebastopol will best prove this, and
at the same time it will give an opportunity to convey a still
clearer idea of the bearing of Burbank's methods and results
on the science of evolution.

In the first place, the occurrence of elementary species
in nature often opens definite possibihties for culture and
selection. Burbank showed me a highly interesting sport
of a Mahaleb cherry or Prunus Mahalcb. It grew in a Httle
grove of shrubs of the same species, on his Sebastopol farm.
It had yellow berries instead of black ones and showed some

224 PLANT-BREEDING

corresponding smaller deviations from the average type.
He uses the species for stocks for grafting and had sown them
from seed which he had received from the southern states.
From one of these introduced seeds the sport had arisen.
There could be no doubt that it was due to a real mutation,
and it was manifest, also, that this had been produced be-
fore the introduction. But whether the deviating specimen
itself was to be considered as a mutant, or whether, perhaps,
in the original locality an old yellow ^^ariety of Mahaleb
cherry existed, he could not tell. It was noticed here for
the first time, but whether it was old or new, nobody knew.
It was, however, a most typical sport. Elementary species
among trees have not yet been given the interest which they
deserve. The apples, pears, hav^horns, and some others
have yielded numerous types, either for industrial culture or
for scientific description. Oaks and walnuts differ in the
same way, and there can hardly be any doubt that this
is true for a large number of deciduous and even of conif-
erous trees, also. A scientific distinction and industrial
test of these elementary species might probably lead to a dis-
tinct improvement of many of our forests and groves, giving
more uniform crops of nuts, or harder and better lumber, or
a more rapid growth, or more straight and less branched
stems, etc. A combination of the results which Nilsson ob-
tained by his sharp distinction of the elementary species of
cereals, with the possibiUties indicated by the hybrid walnuts
and other trees of Burbank, might open large prospects of
improvement in forestry.

In many cases it is doubtful whether a sport is due to a
mutation or to extreme fluctuating variability. The fra-
grant varieties of Calla, DahUa, and Verbena may be cited
as instances. The first of them has already been alluded to,
but the production of the two others deserves a more detailed
description. Along the fence of his garden, in front of his

BURBANK'S HORTICULTURAL NOVELTIES 225

house, a large row of fragrant Verbenas was in full bloom,
at the time of my last visit. It was the ordinary European
garden-type, but of a uniform pale pink color. All of them
were manifestly derived from cuttings from one individual.
They had the most deUcious flavor of the traihng Arbutus,
Epigaea repens, a much-beloved creeping herb of the eastern
woods. Burbank told me that, years ago, when busy in the
selection of his Verbenas, he was struck by a faint odor from
some of the flowers. He did not, however, succeed in sin-
ghng out the fragrant individual. Next year, he noticed the
same odor and was able to isolate the sporting plants. He
saved and sowed their seeds, got better scented specimens
among the offspring and selected and isolated these. After
some years of selection the fragrance was noticeably in-
creased and the variety received the name of "Mayflower."
It is not constant from seed and it is not known whether it
can be made so or not. Ordinary Dahlias have a some-
what disagreeable odor. This has been driven out and
replaced by the sweet fragrance of a magnolia blossom of
the glauca species. The origin of this race was a single
plant with a faint fragrance, which Burbank noticed, several
years ago, on one of his beds. Through isolation and repeat-
ed selection the fragrance has been increased and fixed, and
the variety purified from its hybrid admixtures, but, as yet,
it is not sufficiently fixed to reproduce itself purely from seed.
Whether the original variant was itself a hybrid between an
unnoticed fragrant parent and the ordinary form, or only a
minus- variant of the new fragrant variety, it is now, of course,
impossible to decide.

Fragrance in fruits is often discovered and improved, in
the same way, by Burbank. Even among walnuts he has
produced a fragrant variety. More interesting, from a prac-
tical as well as from a scientific point of view, is the sweet
walnut which lacks the bitter tannin in the coat of its nuts

226 PLANT-BREEDING

and in the thin shell of its seed. As a variety it has been
given the name of wliite walnut. Its nuts are white and do
not need the artificial bleaching of the other sorts to which
the tannin of the coats gives their dark appearance. The
pit on the inside of the nut is of a pure wliite and sweet,
because the astringent taste of the shell and the meat has been
taken away from it. Tliis variety was started from some
of his hybrid nuts wliich, at first, gave some indication and
promise of success in this line of improvement.

In contrast to these pure sports I now mention the cases
in which a combination, obtained by means of a cross, is
so strikingly different from what could be expected that it is
instantly designated a "sport." The Bartlctt plum is such
a chance seedhng among the plum hybrids of the Sebastopol
farm. We inspected the tree, but the fruit was not yet
ripe. It is quite different from other plums. It branched
from its very base and had erect shoots with a fine pecuUar
foliage. Its plums have the taste and fragrance of a Bartlctt
pear, and even the meat resembles that of this well-known
fruit. Visitors whom Burbank requested to eat it v/ith
their eyes shut, have taken it for a pear. It sprang up in a
lot of hybrid seedUngs, most of which had been produced
by crossing the Kelsey and the Simoni, but for this individ-
ual seedUng the ancestry could not be traced. It is, how-
ever, an evident combination, and all of its qualities can be
traced to its probable parents, the flavor being mainly due
to the Prunus Simoni.

The stoneless prunes and the spineless edible cacti
are such evident hybrids that it is doubtful whether anybody
would designate them as sports. I have already given a
general description of them, but shall now add some details.
About the year 1887, Burbank received his first "prune sans
noyau" from a French nurseryman. It soon fruited and
produced a fruit about the size of a small cherry. It was

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228 PLANT-BREEDING

crossed with the French prune, Petite d'Agen, which is
widely spread in CaHfornia culture, and with other prunes.
About 1893, the first hybrid fruits ripened. Numerous
crosses had been made, numerous hybrids had to be tested.
Only a small proportion of the seedlings were stoncless, and
most of these showed the undesirable qualities usually found
in seedlings. It was only in 1899 that a good palatable
stoneless prune of sufficient size appeared. This has been
given the name of Miracle, and is now being brought into
the trade by the Oregon Nursery Company, at Salem,
Oregon. It combines the main character of the " prune sans
noyau" with the good c|uaUties of the Petite d'Agen, while
hardiness and bearing qualities are characteristics of both-
parents. It docs not contain sugar enough to be classed
among the drying prunes, but for cooking it must supplant
the well-known Damsons, being larger and more productive
than any of them.

The spineless edible cactus combines, in the same way,
the main character of its spineless parent with the excellent
ciualities of the ordinary cultivated varieties. It has excel-
lent fruit of a new flavor which may be eaten fresh or
cooked. As food for cattle the stems are very rich; they are
estimated to be at least one half as nutritious as alfalfa (Lu-
cerne clover). The production of this variety started from
five species of Opuntia imported from different countries,
the names of some of them being unknown at the time.
Among them was a spineless, but small and insignificant,
species from Central America. These he has crossed and
re-crossed with the cultivated varieties, selecting for vigorous
growth and superior food-bearing cjualities. A number of
European and African varieties of Indian Figs were sent to
him and the Opuntia vulgaris, O. Engelmanni, and other
hardy types were mixed with them. The beds, which I saw
in 1906, showed hundreds of specimens which had been

22y

230 PLANT-BREEDING

planted in the spring and had already produced a first set
of numerous disc-like branches. They were expected to
make two or three more sets in the same year and to fill in
the large spaces which were left between them at the time
of their planting. They varied in the size, form, and color
of the pods, and probably, also, in their nutritious quaUties,
and were grown as a direct test of these points. The value
of these hundreds of plants which will, on the average,
produce fifty pods each in a year, may be deduced from the
fact that he had sold five of the pods to an AustraUan firm
and was building a new and larger residence from the sum
they had brought him.

It would, of course, add highly to the value of this race
if it could be made constant from seed. It is evident that
a rapid spreading, as well as the treatment on the farms,
would be made more easy by such a change. I saw numer-
ous wooden seed boxes with small seedUngs, but almost all
of them were spiny. Thousands were rejected, and only those
which showed a distinct diminution of their spines were
selected and planted out. Large beds with young spineless
plants were seen in his garden. Burbank estimates, from
the present extension of uncultivated lands fit for the pro-
duction of cacti, that his spineless and edible varieties may,
in time, double the population of the earth. At least they
promise to do more for the world, in a material way, than
any other of his productions, but much work will still be
required before even an essential part of his hopes can be
brought into execution.

Beautiful and striking sports are sometimes offered by
hybrids which revert to a quality of one or more of their
pure ancestors, this mark not yet being displayed in the
previous hybrid generations. An instance of this we admired
among his Callas. Hitherto his hybrids had varied in the
color of their spathes from white to a more or less intense

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232 PLANT-BREEDING

yellow. During my last visit one of the seedlings, however,
opened its sheath with a purple color, reminding us of its
forefathers, Rehmannii and Nelsonii, with their pink, rose,
and purpHsh hues. But in this hybrid the color was deep-
ened, covering almost the whole of the flower, and was thus
evidently improved.

Hybrid poppies are hable to reversions, also. Burbank
crossed the oriental poppy, which is a perennial herb, with
the snow-white, double and fringed flowers of "the Bride"
and some other varieties of the common opium poppy. I
have already referred to these crosses and their high degree
of variabihty. On my last visit, I saw a large bed in full
bloom repeating almost all the known color varieties of
double poppies, and varying in many other directions. He
also crossed this Bride variety and some others with a wild
and scarcely cultivated smaller species, the Papaver pilosum,
which has pale orange flowers. Among the oft'spring some
were fringed and some double, but the most curious fact was
that some produced colors not intermediate between, or like,
those of the varieties named, but returning to the original
type of the whole somniferum species. The special causes
of these atavistic reversions, however, remained obscure.

Bud sports are one of the most typical kinds of sports.
Burba.nk cultivated one of them. It was the Pierce's grape,
which originated, some time ago, as a branch on an Isabella
grape on xVlr. Pierce's farm at Santa Clara, Cal. It is well
known for its large and superior fruit. It comes true from
seed but is hable to sport in this way from time to time. The
sporting seedlings dift'cred from the average in the shape,
color, and hairiness of their foliage and in their mode of
growth; but, at the time when I inspected them, they were
still too young to produce fruit.

Other bud sports Burbank has not observed, so he told
me. Of course, the sports with variegated leaves are to be

BURBANK'S HORTICULTURAL NOVELTIES 233

excluded. Such arc common in almost all the larger nur-
series. Sometimes they come from buds, sometimes from
seeds. A case of the latter belonged to a hybrid between
the oriental and the opium-poppy, of wliich he showed us
three large specimens with the foliage of the oriental parent,
Init with beautiful pale yellow borders and streaks on the

Fig. 72. A. The variety of the Bride of the Opium Poppy. B. The wild
species Papaver pilosum. C. The hybrid of these two poppies.

leaves. It scarcely flowers and is wholly sterile, but may
easily be multipHed by division.

Whether the thornless brambles, previously alluded to,
constitute a mutation remains to be investigated. During
the days of my last visit, they flowered for the first time;
their long stems and numerous leaves being as smooth as
when the plants were selected from the seed boxes.

234 PLANT-BREEDING

A chestnut without spines on its burs was growing on
the Sebastopol farm. It was a single young tree, found
among the numerous offspring of a cross between the Japan-
ese and the American species, both of which have spiny burs.
It was, probably, a pure mutant.

A blue poppy which appeared in his crosses of Papaver
Rhoeas and allied species has already been referred to. It
was, also, probably, a pure mutation, which, however,
showed itself, in the beginning, only in an imperfect degree
of development.

The same holds good for his scarlet California poppy
(Eschscholtzia caUf ornica) . He discovered the first indication
of this mutation, some years ago, when inspecting large beds
of ordinary yellow California poppies. One flower caught
his eye; it had on one of its petals a fine longitudinal line of
scarlet color. It would, surely, have escaped the eye of
most other men, but to Burbank it betrayed the capacity of
this one plant to produce a variety of a new and unsuspected
color. He isolated the plant and saved the seed. Among
the offspring the scarlet color was repeated, but still to an
insignificant extent. He repeated the selection during some
years until he got a race of a pure and uniform scarlet color
in all the flowers and on all the plants. We saw large beds
in full bloom but without atavistic reminders of the yellow
prototype.

It would be a most interesting task, full of promise, to
try to repeat the observation of the appearance of all these
mutants and to follow their origination and their develop-
ment under the rigid conditions of scientific research. It
might be expected that the material from which Burbank
started would, probably, repeat the mutation, even as other
horticultural and experimental mutations are known to have
been produced repeatedly. In doing so an exact history
might be given instead of the more or less vague and incom-

BURBANK'S HORTICULTURAL NOVELTIES 235

plete reminiscences of the breeder, and a basis might be
worked out, from which scientific conclusions of the highest
importance could be drawn. Burbank often claims that
the production of a single novelty requires much time and
much labor and a considerable amount of space in his garden
during a series of years. The scientilk repetition and de-
scription of such a mutation experiment would, however,
require perhaps ten times as much time and labor as the
practical production of the same variety.

In one instance I have had the good fortune of producing
experimentally a variety, the exact counterpart of which has
been produced industrially by Burbank. I refer to the
origin of a double marigold. Burbank is doubhng his Shasta
daisy, and in my garden I observed and guided the springing
up of a double form of the yellow corn-marigold (Chrysan-
themum segetum). Although Burbank's description of this
selection is only very short and succinct, there cannot be the
least doubt concerning the paralleUsm of the two cases.
The Shasta daisy is, as I have already pointed out, a hybrid
between a Japanese, an American, and an English species of
the genus Chrysanthemum. Among them, at least the
Enghsh ancestor is highly variable, and it is evident that the
fluted rays, and some other remarkable deviations which
occurred in the hybrids, may be due to this source. The
same holds good for the doubhng. Ten or fifteen years ago
Burbank discovered a sUght degree of augmentation in the
number of the ray-florets of some of his hybrids. He care-
fully isolated them, observed an increase in the deviation
and repeated the selection until the flower heads became as
double as those of any other double variety among the Com-
posites.

In the case of my yellow corn-marigold the selection has
been accompanied by the counting of the ray-florets for all
the plants of the succeeding generations. The first indica-

236 PLANT-BREEDING

tion was one supernumerary ray on each of two flower heads
of a single plant. Sowing the seeds of this individual, the
numbers were seen to increase rapidly but all the ray-florets
always belonged to the outer rows of the heads. After a
selection of three years, suddenly an individual appeared
which had some stray ray florets scattered among the tubular
florets of the center of some of its latest flowers. The seeds
of this plant at once gave the desired double variety. x\ll
the progeny produced more or less double flower heads, the
number of the rays ranging, in the best instances, from
100 to 200. In the following year, the race could be some-
what purified and thereby improved, but the type was not
essentially changed and has since remained constant. The
appearance of the first ray-florets among the little
central tubes would, of course, easily have been overlooked
and the increase of the number of the rays would have seemed
gradual throughout. The selection would have obscured
the mutation, as has, probably, been the case in the produc-
tion of many other horticultural varieties.

V

THE ASSOCIATION OF CHARACTERS IN
PLANT-BREEDING

A. ASSOCIATION OF CHARACTERS IN NATURE

The doctrine of evolution is so closely associated with
the interests of man that each phase of its broad lines of
teaching commands our special attention. Amelioration
of domestic animals and plants is one of the prevailing feat-
ures in agriculture and horticulture. The laws wliich
govern these practical endeavors as well as the scientific
investigations are now being slowly disclosed. Many of
the common questions which puzzle the horticulturists can
be answered only by appealing to these laws. The problems
involved arc, however, many-sided and in order to gain a
distinct knowledge and a clear insight into their different
methods of research it is nowadays unavoidable to divide
the subject into its separate parts.

Some Unes of research may guide us along the paths of
anatomical and histological development; others are related
to the more common but equally significant facts, wliich may
be gathered by observations in the field. These latter are
vitally related to the study of organic evolution, and often
have a direct bearing on the practical processes of breeding.
Agricultural plant-breeding is the evolving of useful qual-
ities. But what are qualities and how may they be discerned
and studied?

For many years this question has been considered as a
very simple one, easily to be answered on the basis of our
common knowledge. Of late, however, this attitude has
completely changed, and the intimate nature of qualities
and characters has become an object of most intense inter-
est for the practical breeder as well as for the student of

237

238 PLANT-BREEDING

evolution. Experience has taught that qualities are often
associated with one another by distinct laws, and that a
knowledge of these laws may give us a power over them,
greater than any man has heretofore aspired to. Even a
suspicion of the meaning of these laws, or an intuitive appre-
ciation of their work, may lead to valuable results, if it is
only combined with a thorough knowledge of the species in
question.

Before going into the details of my subject I wish to con-
vince my readers of the truth of these assertions by giving
some noticeable illustrations. The first is an old one, the
second is afforded by Burbank's work, and the third is taken
from Nilsson's experiments in agricultural breeding. It
will not be necessary to go into many details, since even with-
out them their bearing will be clear enough.

The common stock (Matthiola incana) is cultivated in
double-flowered and in single varieties. The singles are
pure, but the seed for the doubles is saved on single- flowered
specimens belonging to the same variety. From these seeds
about one half give double and the other half single flowering
plants. The doubles, however, obtain a higher price on
the market, and it is therefore of some interest to separate
and isolate them as early as possible. In France this is
done by children, who pick out the singles and spare the
doubles. This is done while the plants are ver>' young,
having produced a Httle stem with some small leaves, but still
without branches and without flower buds. It is impossible,
therefore, to distinguish them by these buds, but there are
shght differences in the color and the hairs of the leaves,
which separate the doubles from the singles for the expe-
rienced eye. These differences, however, are so very sHght
that it is impossible to put them into words or even to explain
them to the layman. No botanist, as far as I know, has
as yet succeeded in recognizing them, and nevertheless the

THE ASSOCIATION OF CHARACTERS 239

children of the nurseries are seldom mistaken in their choice.
Hence, we may conclude that the character of the doubles
penetrates the whole plant and produces small changes in
all the organs, even at the very earliest periods of their
development.

For my second illustration I choose Burbank's selection
of quinces. A thorough study of this genus has enabled
him to see relations between the qualities of the fruits and
the characters of the foHage. Thereby it has been possible
for him to judge of the value of new acquisitions or to com-
pare the different specimens of a hybrid culture, long before
the time of blooming. Thousands of young seedlings may
be estimated in this way, the unpromising ones being
thrown away before they have to be planted out, and by
this means, of course, much space and labor is saved. The
differences between the seedhngs are, some of them, so great
that they may be appreciated by other people too, but others
are so slight that they escape general observation. But in
the first case their relation to the qualities of the fruit is hid-
den from the eye of the ordinary horticulturist, and it is only
by means of a special knowledge of the plant, and an intui-
tive appreciation of its virtues that Burbank could make
these remarkable selections.

IMy tliird example is taken from the selection of cereals
on which Nilsson, the director of the experiment station of
Svalof in Sweden, is working. The barley, as cultivated in
the central parts of Sweden for the purposes of the brewers,
was generally suffering from the weakness of the straw,
which caused it to lie down in unfavorable summers, thereby
often involving the loss of large parts of the harvest. After
many years of unsuccessful efforts to improve this barley
in order to give it stronger halms, Nilsson decided to solve
the question in quite another way. He gave up the selec-
tion of the ordinary sort, the so-called Chevalier barley, and

240 PLANT-BREEDING

proposed to look for tne same qualities among other sorts
with resistant halms. A minute study of the botanical char-
acters of the ears, of their spikelets and scales led him to the
discovery of a relation between the form and the hairiness
of the latter and the practical qualities of the grains. On
the ground of this relation tens of thousands of individual
barley plants were scrupulously investigated, and some sixty
were chosen out of this number for a comparative trial of
their progeny. Among these the continued study during
subsequent years led to the selection of the one which best
answered the proposed question, inasmuch as it combined
the equalities of a fine brewers" barley with strong and resist-
ant halms. From this one plant a race has been derived,
wliich received the name of Primus-barley and has already
supplanted large parts of the cultures of the original Cheva-
lier kinds all through the middle parts of Sweden.

These examples may suffice to convince us of the useful-
ness of a thorough study of the association of qualities and
characters of cultivated plants. Evidently such a study is
a very difficult one, but it opens new and broad lines of re-
search. In order to build upon a scientific basis, it is nec-
essary not to confine ourselves to cultivated plants, but to
take as large a view of the whole vegetable kingdom as possi-
ble. Only in this way is there a chance of discovering the
great laws of nature which govern this most intricate group
of phenomena.

Broadly speaking, the characters of plants may be con-
sidered from a systematic or from a physiological point of
view. The systematist explains the affinity by means ot
the laws of inheritance, assuming thereby a common cause
for every character wliich remains unchanged throughout
a large group of closely related species. The flower heads
of all the composites must have one and the same cause, and
so it is with their inferior ovary, their connate stamens, and

THE ASSOCIATION OF CHARACTERS

?4i

many other characters. This cause, though hidden from
our eye, and showing itself only in its effects, must be the
real character, which by means of heredity has come to
be present in all members of this large family. We may
assume it to be pure and simple, even if it is never allowed to
show itself as such, but must always become visible in com-
bination with the other characters of the same species, and
may be changed by them to
a greater or lesser degree.

The physiologist has re-
marked, however, that the
laws of heredity cannot be
the only cause of the simi-
larity among plants. In
innumerable cases there is
a Hkeness which cannot be
explained by a common
origin. The spurs of the
orchids and of the violets,
of the toadflax and of the
columbine are evidently the
same organs, playing every-
where the same part of pro-
ducing honey for the visiting insects. Notwithstanding their
differences in size and color, and even in the manner of
secreting their product, there can be no doubt as to the
identity of the primary cause wliich has produced them.
On the other hand the plants which bear them belong to such
widely divergent famihes, that it is simply impossible to
look for a common origin in order to explain this repeated
occurrence of spurs.

So it is in almost every case, for characters of the high-
est systematic value as well as for minor marks. Inferior
ovaries are found among dicotyls and among monocotyls,

Fig- 73-

Flowers of columbine, show-
ing the spurs.

242 PLANT-BREEDING

gamopetalous flowers occur in the mallows and in the hya-
cinths, symmetrical corollas and decussate leaves are spread
over the families of the natural system in the most capricious
manner, and even the forms and structures of the leaves do
not show any relation to systematic affinity. Assuming the
same causes for the same phenomena, the physiologist is
led to the conclusion, that the visible characters must be the
result of internal properties which may be the same in widely
different groups of plants. These internal qualities may
pass from species to species by the laws of inheritance or be
produced anew in distant famihes and genera.

The chemist tries to connect the visible properties of his
substances with the assumed qualities of molecules and atoms,
and to explain, by this theory, their conformities and their
divergencies. In the same way, the physiologist explains the
likenesses and the differences of his plants, by the assump-
tion of equally invisible units, which are supposed to under-
lie the visible phenomena. These units he calls unit-char-
acters. For him they are the resting pole in the ever-mov-
ing tide of the outward forms. On this principle he tries
to explain the common features of plants, independently of
the question whether they are closely related or belong to
distant groups. It is a wide field for observations and induc-
tions, but the study heightens our appreciation of the real
nature of all living beings. It is a kind of biological analy-
sis, leading to a knowledge of the intimate elements of which
the plants are built up.

The study of these elements or unit-characters has led
to the discovery of a most significant phenomenon. It is the
regular coincidence of marks, which hitherto had been re-
garded as quite independent from one another. This asso-
ciation has been shown to obey natural laws, and the study
of these laws enables us to predict one mark from the obser-
vation of the other. The relation of the color and form of

Fig. 74. The deadly niglitshade, or Atropa Belladonna. A. Brown
flower, and B. Black fruit of the species. C. A twig of the yellow variety
with pale flowers and yellow fruits.

243

244 PLANT-BREEDING

the young seedlings of the stocks to the shape of the flowers
is only an instance of the general phenomenon of association
and so it is with the marks which enable Burbank and Nils-
son to make their selections.

These coincidences are called technically, correlations,
and it is these which I have chosen for the subject of this
chapter.

Some of them are of a simple and obvious nature, and
their internal cause may easily be understood as soon as the
association has been pointed out. Such instances may serve
as a basis for further discussions, and become a guide into
the more intricate cases.

It is a common experience that many color-varieties of
plants may be distinguished by their seeds. This rule holds
good for garden plants as well as for large crops. A dark
color of the seed indicates a bright flower, a pale seed is
usually associated with white or pale corollas. Stocks have
grayish, brown, or bluish seeds according to the color of their
petals. Among the lupins the red and blue forms may often
be distinguished by their dark seeds, but the white variety
has white seeds (Lupinus angustifolius). White vetches
have, as a rule, yellow or greenish seeds, in contrast to the
dark seeds of the common species. The true opium poppy
has white flowers and pale seeds, and many other garden
varieties of this plant differ in their flowers and seeds in a
more or less corresponding degree.

In all such cases there can be no doubt, that the coinci-
dence is a real correlation, and that the cause, which darkens
the flowers is the same as that which is active in the seeds.

Berries often show the same correlation to the flowers.
If a species has red or blue corollas combined with dark
berries, its white variety will often show pale or even white
fruits. One of the most interesting instances of this rule is
the pale variety of the belladonna, a very poisonous plant.

Fig. 75. The long-leaved Veronica {Veronica
longijolia).

245

246 PLANT-BREEDING

which grows in many forests of Germany. It has brownish
flowers and large and shiny black fruit, the color consist-
ing of two factors, a yellow and a red one. A variety of this
species was discovered by Schiitz in a wood in the neighbor-
hood of Calw in Wurtemberg about the middle of the last
century (1851; cf. Hoffman, Sp. et Var., p. 87), It has pale
greenish flowers and bright yellow berries. It comes true
to its character from seed, and is often cultivated in botani-
cal gardens. The red dye or anthocyanin, which darkens
the corollas of the species and is concentrated in the fruit
to a degree that makes it black, is absent in both organs
in the variety, the yellow not being affected by the change.
Evidently the red dye is the same color in both organs,
and as soon as it became latent by the production of the new
form, it disappeared simultaneously from the flowers and
from the fruits.

In many species this anthocyanin is not limited to the
flowers and the fruits, but may be displayed in the foKage
also. The stem and the branches, the leaves and their
stalks, and even the bracts of buds and the coats of a bulb
may be imbued with the color. It very often happens in
such cases that the white or pale varieties show their marks
in the correlated organs. As the first example, I choose the
thorn-apples. They are known in a white and in a blue
variety, the flowers of the latter being of a pale blue. The
colored form (Datura Tatula) has stems and leaves of a
brownish color, but the same organs are of a pure green in
the white-flowering plants (D. Stramonium). Even the
young seedhngs may be distingu-'shed by the tinge of color on
their stem, and whenever the dark ones are separated from
the pale, all of the first will bear blue flowers and all of the
latter white.

It would be easy to give a Hst of such examples, especially
of garden plants, since horticulturists often select their seed-

THE ASSOCIATION OF CHARACTERS 247

lings by this mark, thereby being enabled to throw out the
"rogues " long before the time of blooming.

Perennial herbs may show the same correlation. In the
colored forms the young shoots which arise from the root-
stocks have a dark tinge, but in the white varieties they are
pale or colorless. The willow-leaved Veronica (V. longi-
folia) affords an instance, which has proven useful in the
study of the bud-variations of its hybrids. The hybrids of
this plant have the same blue flowers as the parent species,
but if one of the parents used for the cross was the white
variety, these blue hybrids are apt to produce groups of
white flowers. Such groups may consist of a few corollas
upon a blue spike, or may form a longitudinal Hne, leaving
the flowers on one side uncolored, while those on the other
are blue. Or a whole raceme may be white on a plant, whose
remaining spikes are of the ordinary color. Lastly, a stem
arising from the root may have returned to the type of the
white parent. In these latter cases the color can be pre-
dicted from the very first beginning in the growing buds,
and the whole stem, with ah its branches and leaves wifl be
of a pure green instead of showing the brownish tinge of the
species.

Bulbs of hyacinths may seem to the layman to be all
alike, but the breeder is often able to distinguish their varie-
ties bv their size, the number of their Uttle side bulbs, the
form of their top, and especially the color of their outer coats.
The correlation between the marks of the dry and market-
able bulbs and the characters of the flowers is so highly
developed that the Dutch bulb-grower Voorhelm is said to
have been able to distinguish more than a thousand varieties
of hyacinths solely by inspecting their bulbs.

Another instance may still be added. It relates to the
association of the color in the bracts, the foliage, and the
flowers in the flowering currant (Ribes sanguineum). This

248 PLANT-BREEDING

species, of which a number of types are growing on the hills
of California, is a very common shrub in European gardens.
It has produced a variety with whitish flowers, which, how-
ever, still betray their origin by a pale red hue. From time
to time it returns to the parent type in the way of bud-
variation, producing branches with dark red flower spikes. If
now we compare such a branch with the remainder of the
shrub, we find that the difference is not hmited to the flowers.
Quite on the contrary, it shows itself also in the bracts and
even in the stalks of the leaves. The bracts are reddish
when the flowers are bright, and almost colorless when the
spikes are to become white. At the first opening of the buds
the color of the flowers may be predicted by this means for
each spike of the variable shrub.

Before leaving the correlations of organs in regard to their
color, I wish to point out another side of the question, which
may throw some Hght on the intimate nature of correlative
changes. The anthocyanin dye is assumed to be, in its
chemical composition, related to the large group of tannins,
of which the common tannic acid is the best known instance.
Hence we may suppose the existence of correlations between
the color and the taste, or, going one step further, between
the color of the flower and the taste of the fruit or seeds,
since tannins may give a peculiar, disagreeable, astrin-
gent taste, as is well known in the case of many unripe
fruits.

Such associations from time to time occur. As an in-
stance I may quote a variety of the Windsor beans(Vicia
Faba), newly introduced by the Dutch seed merchant Van
Namen, in Holland, from which the black patches on
the wings of the flowers are absent. Correspondingly the
young seeds, at the period when they are best for canning,
are of a paler color and a sweeter taste than the ordinary sort.
This sweetness is caused by the absence of the tannin in

Fig. 76. The laciniate bramble (Ritbus Jntt'cosiis laciniat us) with divided
petals. B. A flower of the ordinary bramble.

249

250

PLANT-BREEDING

their coats. By this means the improved variety may be
distinguished by the marks of the flowers.

Besides their color, the foHage and the flowers may be
correlated in their form. The most striking instance is
that of those varieties which have laciniate leaves and
repeat the same character in their petals. Two notable
plants give proof of tliis assertion. One of them is the lacin-
iate form of the ordinary celandine, and the other a variety
of the common bramble. Its petals are divided into three
equal lobes, which in their turn may show small incisions
at their top. These are evidently analogous to the repeated
divisions of the lobes of the leaves.

All the cases hitherto given were related to homologies
between flowers and other organs. But even within the
flowers correlations may be observed. They arc of numer-
ous patterns, but I must limit myself to one instance. As
such I choose the size of the flowers and the relative length
of the style and the stamens.

It is a fact of daily observation that many small flowers
do not need the help of insects for their fertilization. In a
large number of cases their stamens directly touch the stig-
ma, and the pollen is spread over it by the very act of the
opening of the anthers. Many of our common species of
the large family of the cruciferous plants give instances of
this. On the other hand, great size in flowers is often com-
bined with the production of stigma and anthers at such a
distance that the pollen can only reach the first by the aid
of bees and other visitors.

In the evening primroses, as in many other plants, the
size of the flowers depends upon the season in which they
open. This dependence may go so far as to change the whole
biological aspect of the flower. In the ordinary sorts of the
evening primroses (CEnothera biennis and allies), the style
is short and the anthers are arranged around the stigma.

Fig. 77. A. Ordinary celandine {Chelidoiiiitm majiis). B. Laciniate
celandine (C. in. laciniatum), which originated from A in a garden at Hei-
delberg about 1590. a and h. Flowers of A and B.

252

PLANT-BREEDING

They open half a day before the petals expand the flowers
and invite the insects to a visit. During these last hours,
within the closed bud fertilization usually takes place, and
all is over before the insects come, insuring in this way a

Fig. 78. Flowers of Evening Primroses, deprived of the petals. A.
The ordinary species, {Oen. biennis), a self-pollinating species, collected
near Chicago. B. Summer-flower of Lamarck's Evening Primrose, the
stigma protruded beyond the anthers. C. A late flower of the same plant
with the anthers touching the stigma.

most complete self-fertiHzation. Often I have seen the
buds drop off before opening without the least detriment to
the ripening of the fruit. In other cases I succeeded in
cutting away the buds about an hour before their time for
opening, but the young fruits had already been fertiUzed

THE ASSOCIATION OF CHARACTERS 253

and they ripened quite in the ordinary way. All the bright
display of broad and shining petals, of honey, and a sweet
fragrance is here absolutely useless and superiluous. Moths
and bees are attracted in large numbers, but the pollen
which they bring to the pistils is of no use at all.

The evening primrose of Lamarck widely surpasses its
congeners in the size of its flowers. In connection with
this difference it produces styles of such a length that the
stigmas are elevated above the anthers and cannot directly
be touched by their pollen. Here no fecundation is possible
without the aid of the insects, and if these are experimentally
excluded the flowers fade away without making fruit. All
the beautiful and ingenious means of attracting insects come
into play in this case. No part of the flower is superfluous,
as it is in the ordinary species.

The correlation between size and need of insect aid,
however, shows itself as soon as the season draws to its close,
or rather as the spikes increase in length. Towards autumn
the flowers become steadily smaller and their styles do so
too, but in a greater degree. The elevation of the stigmas
above the anthers decreases, and in September and October
they are touched by the pollen, insuring by this means self-
fertiUzation without other aid. The depositing of the pol-
len on the stigma is at first only shght and insufficient, but
as the summer decUnes it steadily becomes more complete,
and in the end the small flowers at the tops of the spikes
are as sure to fertiUze themselves as are the brightest blos-
soms of the CEn. biennis.

If now we compare tliis case of correlation with the
previously mentioned ones, we see that here we have a de-
pendence on external influences, which causes the correla-
tion to come into play, whilst in the other instances no such
excitement was required. Hence we see that all correla-
tions are not of the same nature. Some are the result of

254 PLANT-BREEDING •

the inner qualities or characters of the plant, but others are
the product of reactions to external stimuli.

The difference observed in these cases may be considered
from a broader point of view. Some cases of correlation
are caused by characters which may become active in more
than one organ of the plant. The faculty of producing the
anthocyanin dye may display itself in flowers, fruits, and
seeds, in stems and stalks, in leaves and scales, in one word,
in almost all the organs of the plant. It is evidently every-
where the same character, even where it sweetens the taste,
by lessening the amount of tannin. So it is with the lacinia-
tion, which may affect leaves and petals. In all these cases
the idea of unit-characters is pressed upon us. It is the
assumption that the same unit becomes active in the dif-
ferent parts of the same organism.

In the other cases different qualities may depend in the
same manner upon the changes of the environmental con-
ditions of life. If these are favorable all will increase, but
under adverse influences they will decrease together. In
tliis way different unit-characters may be correlated but
the relation is more in the nature of accidental coincidence
than of actual identity.

All in all, the study of these correlations is of the highest
interest, as well for science as for practice. By means of
them wc may predict one quahty or one function from the
study of others. Insignificant characters or organs may
show us the way and guide us in our selection. The more
we famiUarize ourselves with such seemingly subordinate
marks, and with their relation to the qualities, which deter-
mine the commercial worth of the plant or of the harvest,
the better we shall be prepared for the work of selection.
To judge quinces from their seedUngs, as Burbank did,
may seem incredible to those who are not initiated into
the mystery of this principle, but it can be learned, either

THE ASSOCIATION OF CHARACTERS 255

in practice or on the basis of our general conceptions of
association of characters.

B. CORRELATIONS IN AGRICULTURAL BREEDING

It seems hardly necessary to repeat the evidence given
in the former chapter. We may at once go into the details
and consider those cases, in which the correlations give
direct indications of valuable qualities to the agricultural
breeder. Of course the application of the principle of
correlation to the practice of selection means the judging of
the worth of single plants on the ground of seemingly in-
significant marks.

As a first instance I choose the peas, which have been
studied from this point of view by Tcdin. Peas, as they
are commonly cultivated, are considered as belonging to
two nearly alhed botanical species, Pisum arvense and
Pisum sativum. In reality they consist of numerous ele-
mentary species, which are quite distinct from one another.
More than a hundred types may be distinguished by the
color of the flowers and of the seeds, by the number of the
kernels in the pod, by the disposition of the flowers along
the axis, whether solitary or placed in pairs, by the character
of the ramification of the stem, and by numerous other sub-
ordinate marks. Each of these qualities proves to be con-
stant in pure cultures, and each is correlated to some feature
which may be of influence on the harvest. Among them the
time of the beginning of the flowering period is related to the
period of the ripening of the seeds in so simple a way, that
it may easily be understood, and that we only wonder how
it has been possible that it has not previously been discovered.
Some individual plants produce their first flower in the axil
of one of the lower leaves of the stem, but others are bare of
flowers over a notable length. Now it would seem that this
was only a case of fluctuating variability, the length of time

256 PLANT-BREEDING

required for the beginning of the blooming period varying in
the different individuals. If this were so, the character would
only be of slight value, and, in the main, dependent on ma-
nure and culture. But Tedin found that there are a number
of types, differing from each other in the age in which they
begin to flower, and that each is constant, when propagated
from pure seed. Moreover he observed that the early- flower-
ing plants are early in ripening their seeds too, while the
late-flowering individuals bring their harvest only in the
latter part of the season. That tliis would hold good for
the first pods, might be expected, but the observation showed
that the rule is applicable to the whole harvest.

Earlincss of ripening often is a most prevailing point in
the determination of the cultural worth of a variety. The
influence of unfavorable weather, such as often occurs in
the latter part of the summer, is thereby eliminated. Heavy
rains may bring the necessity of harvesting in a moist con-
dition. Warm and damp weather without sunshine may
induce the plants to produce a rich fohage consuming the
nutriment for the pods and thus deteriorating them. Cold
days protract the process of ripening and thus prolong the
exposure to insect pests. All kinds of dangers speak in
favor of the cultivation of early varieties.

Such may now be secured by the correlated mark of
the place of the first flower on the stem. On the ground of
this mark promising plants are selected and isolated in
order to determine their worth afterwards, in their own
harvest and in that of their progeny.

Apples and pears may give a second instance. In the
first half of the last century the Belgian horticulturist Van
Mons discovered the significance of their numerous elemen-
tary species and the relation between their fruits and the
form and growth of their foliage and branching. Since his
time much has been done for the amelioration of these im-

THE ASSOCIATION OF CHARACTERS 257

portant trees, and numberless new varieties have been pro-
duced. Among them, more than once it has been the aim
of the breeder to obtain seedless fruits, and shortly after
the time of Van Mons some such types have been propagated
and introduced into trade, but without any noticeable suc-
cess. In European gardens, here and there, and not even
rarely, some old tree is still testifying of these attempts. They
belong to more than one variety, as for instance the " Berga-
motte sans pepins" and "Riha's Kernlose Butterbirne."
But as yet no breeder has succeeded in combining the lack
of seeds with other desirable quahties. Of late, in America,
the Spencer Seedless Apple Company at Grand Junction,
Colorado, promises to introduce a new and better seedless
variety of apples.

Now the lack of seeds is directly correlated with some
other valuable quahties. In the first place not only the
kernels are absent, but also the core, and the whole heart
of the fruit consists of succulent and eatable tissue. No
labor has to be spent in boring out the core, when preparing
the apples for conservation, and no useless parts heighten
the freight in shipping. These, however, are not the most
important quahties of seedless fruits. Quite on the contrary,
the relation of the seeds to the nourishment of the tree is
preponderating. The seeds contain the germ of a new tree,
and the nutriment necessary for its first development. For
a large part this consists of albuminous substances and their
production exhausts the tree to a much liighcr degree than
the many times more voluminous, but only sugary tissues of
the whole apple. Seedless trees, therefore, are much less
exhausted by their fruits than ordinary varieties. Their
harvest will be larger with the same consumption of manure
or with the same extension of the fohage and roots, which
absorb the nourishment and prepare and send it to the fruit.
Experience has shown the high significance of this relation

258 PLANT-BREEDING

for the oranges of southern California and many other kinds
of fruit-trees, and we may confidently assume that the same
rule will prevail for all other trees.

Among agricultural plants instances of observed cor-
relations are very numerous. In potatoes richness of flowers
indicates a late ripening of the tubers, an abundance of
seed-berries is related to a smaller production of potatoes,
and in the same way the extension of the foliage, the number,
height and branching of the stems and some other marks
may be used in predicting the quaUtics of the harvest. Flax
may be judged by its stalks. Long and thick stems, nu-
merous side-branches, and numerous pods are assumed to
be indicative of strong development and long and solid
fibers. In hops the late kinds are richer in resinous sub-
stances, but thcii aroma is not so fine as in the earher sorts
and the botanical marks of the hop-bells, such as hairiness,
length of the axis between the succeeding bracts, and many
others may be made use of in judging the value of the differ-
ent varieties. Clovers are very rich in elementary species,
which may be discerned by the form of the leaves, by the
presence or absence of whitish spots on the leaflets, by the
size and the color of the seeds and by some other marks,
correlated with the practical qualities of the types under
consideration. Varieties of vetches (Vicia) in wliich the
stems begin to branch at a short distance from the root are
less sensible to frosts and bad weather during winter than
those which remain unbranched for a longer period. Nu-
merous other instances could be given, showing the interest
attached to a thorough study of apparently insignificant
marks and even of such differentiations as escape the atten-
tion of the ordinary observer.

Instead of prolonging the Hst, however, I prefer to call
attention to some cases of especial interest, in which the
correlations may be more or less clearly understood. One

THE ASSOCIATION OF CHARACTERS 259

of the most prominent features in the value of agricultural
products is found in the size of the seeds, or as it is often
stated, in the number of seeds wanted to fill a liter. Larger
seeds are as a rule preferred, and many regions which are
renowned all over the world for the superiority of their
seed grains, owe this repute in a high degree to their care
in sifting the seeds and separating the biggest ones as well
for the continuance of their race as for sale. It is interest-
ing to look into the reasons for this preferment. In the first
place comes the relation between the useless and the useful
parts of each single kernel. In a seed the inner or nutritious
tissues are surrounded and protected by the outer layers
or integuments. The inner parts may consist of the germ
alone, or of the germ and the albumen, the germ containing
chiefly the albuminous and oily substances, and the albu-
men being ordinarily the tissue in which the starch is the
most prominent nutritive element. The integuments or
outer layers are not only devoid of nutritious contents, but
are also ordinarily of a considerable firmness. They are
built up of different tissues. In the seeds of the clover the
external layer is cuticularized. These coverings have their
significance for the protection of the germ against all kinds
of dangers, but considered in the harvest they evidently
diminish the quantity of nutrient parts per unit of weight.
Hence the conclusion that the nourishing value of a given
quantity of corn, of grain, of peas, or of any other eatable
kind of seed, depends in a high degree on the development of
those integuments. The thicker they are, the less is the
part of the useful tissues, while seeds with thinner shells
contain more nutritive parts, and moreover are more easily
digestible.

Therefore the breeder always has to select the plants
with thinly covered seeds, and the correlation which exists
between this quality and the size of the seeds is his easiest

26o PLANT-BREEDING

and most reliable guide. For numerous determinations
have taught that large seeds have thinner integuments than
smaller ones. This rule holds good for grains and peas
and probably for all agricultural crops, and even for flowers
and wild plants the same relations prevail. The size of the
germ and albumen and the development of the surrounding
layers are evidently dependent on the same influences.
Individual strength of the variety, or a better nourishment
of the single plants will cause both of them to increase.
But the measure of the increment will be different for them,
and therefore their proportion in weight and volume will
be affected by the change. The relation is the same as that
which we have studied in our last chapter for the size of
the flowers and the length of the styles in the evening prim-
roses. Or, in other words, favorable conditions will promote
the development of the inner nutritive parts of the seeds in
a higher measure than that of the less digestible coverings.
The preference commonly given to large seeds may be
explained by the evidence afforded. But the detailed cor-
relation is not the only one. On the contrary, the size of
the seed is correlated with its development during the ger-
minating period, and, through this, has an influence on the
individual strength and size of the whole plant. Moreover,
larger seeds are known to be more equal in size, the smaller
specimens which are so common in non-selected samples,
faihng in them. This conformity results in simultaneousness
of germination and development, two of the weightiest factors
for a regular growth of the crop. Especially they determine
whether at the time of the harvest all ears or all pods will be
duly ripe, or whether a larger or smaller part of them will be
lost. Ripening too early, an ear may lose its kernels before
the harvest, whilst ripening too late it is of no use at all.
A simultaneous development, therefore, is one of the most
desirable qualities in cultivated plants, - and this may be

THE ASSOCIATION OF CHARACTERS 261

reached by selecting on the ground of seeds of equal size, or
simply on the base of choosing the largest seeds. Apart
from these general correlations there are two minor points,
for which I might call your attention. The first is indicated
by the common proverb :

One year's seed
Is seven years' weed.
It means, that a large number of weeds and other wild
plants produce seeds, only a part of which will germinate
in the next spring. Another part will sleep in the soil and
only be awakened in the spring of the following year, whilst
the more resistant kernels will stand two or more years and
come into germination after this prolonged period of rest.
Some spare seeds may even rest as long as six or seven years ;
whence the saying quoted. This rule is not at all hmited
to weeds, but embraces the different sorts of clover and of
other alUed leguminous forage plants.

Now, here also, we observe a correlation between the
size of the seeds and the time required for their germination.
As a rule, the smaller seeds have the thickest and hardest
coats, as we have already seen, and it is exactly the extreme
resistance of the coats, which causes them to He dormant
for so long a time. If we sow seeds of common clover or
of the crimson species (TrifoHum incarnatum) on a layer
of moist blotting paper, we can easily pick out day after day
those which produce their rootlet. In the main the larger
seeds will thus be seen to germinate first, and after a week
or more only the small kernels remain. Among these,
some will germinate during the next weeks, but some spare
ones will remain dormant until the next year.

E\ddently it is of high practical interest, in the first place,
to have all or nearly all the seeds of a sowing germinating
in the same spring, and in the second place to have them all
coming up in the same week or at least as nearly at the same

262 PLANT-BREEDING

time as possible. Varieties with larger seeds are therefore
preferable by far, since they do not contain the aberrant
little ones, which are the chief cause of the loss and of the
trouble.

At the Swedish agricultural experiment station at Svalof
another method has been developed to get rid of this nui-
sance. Though it is not directly related to our main subject,
it is as well to dwell upon it here, for a short time. It has
been discovered that with clover and other leguminous forage
crops the whole question of the sluggishness of the germinat-
ing process is due to the resistance of the outermost layer
of the seed coats to the absorption of water. Small seeds
of clover remain absolutely dry in water for days and weeks,
and in this condition they may even be thrown into boiling
water without being killed. It is the very thin cuticle of
their epidermis which impedes the penetrating of the water
into the inner parts and thus prevents the initiation of that
process of saturation w^hich is the necessary condition of all
germination. If there were only a small hole, or a small
non-resistant spot, the water might pass by this and effect
a complete imbibition. On this principle the Svalof method
is based. It allows of fiUng all the seeds on a small spot,
making their coats locally permeable for water, without
changing them in any other way. In order to do tliis, an
apparatus has been built, which throws the seed against a
filing disk in an obUque direction and in continuous current.
Thereby the culture of many species of leguminous plants
has been made possible and advantageous, which formerly
were disregarded on account of their imperfect germination.
By this means the selection of larger seeds and the applica-
tion of this part of the principle of correlation is made super-
fluous.

My second point is the value of rapidly germinating
seeds in all cases where the germination period is the time

Fig. 79. Panicles of oats. A. With erect, and B. With spreading

branches.

263

264 PLANT-BREEDING

for the attacks of some dreaded disease. For the sooner the
time of sensibility is over, the smaller will be the harm
and the larger the number of uninjured thriving plants.
Experiments have been made in tliis direction in Sweden
on the resistance of grains against the devastations of the
frit-fly (Oscinis frit). This is a httle black insect, attaining
a length of only 2 or 3 mm. and easily recognizable by its
metalUc brightness, black legs, and yellow feet. It invades
the grains chiefly during the germination period, depositing
its eggs on the young plants. The larvag creep along the
leaves and their sheaths downward until they reach the young
halms, and in eating these they destroy the germ of all further
development. Some of the seedHngs may die shortly after-
wards, others may show signs of Hfe during some time, but
their growth is abnormal and for the harvest they are wholly
lost. Whole fields of all kinds of cereals may be destroyed
by this calamity during some few weeks.

One of the best means against the attack of these flies is
the passing of the dangerous period of Hfe as rapidly as
possible. As soon as the young halms are old enough to
resist the invasion, the insects become nearly harmless. On
the basis of our considerations concerning the correlation
of the size of the seeds with the rapidity and simultaneous-
ness of the germination, we may therefore expect that the
sowing of selected large seeds or of large-seeded varieties
vdll give the desired protection. This is exactly the result
of the Swedish experiments. Nilsson and his staff made
comparative sowings of large and of small seeds separated
from one another by sifting, or even by simply choosing the
upper kernels of each spikelet for one trial, and the under
kernels, which as a rule are larger, for the other. By this
method all varietal differences were excluded and the result
was for oats, that the loss from the attacks of the flv was
small for the large seeds, but very notable among the smaller,

THE ASSOCIATION OF CHARACTERS 265

and therefore more slowly and more irregularly germinating
kernels.

As we have already seen, correlations may be divided
into those, which are easily traceable to a common cause,
and those in which the causal relation of the single phenom-
ena remains obscure. In the adduced example of the seeds
this relation is evident, at least to some extent, and therefore
I will now choose a case in which there is no obvious reason
for the connected qualities to be so connected. Our appre-
ciation of the correlation can in such cases only be based
on direct observation. This however, requires a most
minute study, on one side of seemingly insignificant botani-
cal characters, and on the other of the industrial qualities
of the plant.

Among the grains the panicles of the oats give the best
evidence. Their shape and mode of branching are variable
to a high degree. The branches are combined into whorls.
The number and relative development of these branches
proves to be constant for each pure type. The apparent
high variabihty is to be reduced to a large group of single
forms, which when considered for themselves are narrowly
circumscribed and do not transgress their differentiating
limits. Some panicles have their largest branches longer
than the main axis, in others they are shorter. Those of
the first group are ordinarily stiff and dense, those of the
second being more flaccid and more widely spread. The
biggest kernels may be found in the lower spikelets, or they
may prefer the middle and upper ones, and experience has
shown that only such sorts arc commendable which have
their biggest seeds above the middle.

Most reliable marks are given by the color of the seeds.
The sHghtest differences in tint are wholly constant and
indicative of corresponding practical qualities of the sorts.
Yellow and yellowish, straw and reddish-yellow, whitish and

Fig. 80. Svalof Grenadier wheat, the best of the
new Swedish varieties of wheat, very productive of
grain and straw.

266

Fig. 8i. Svalof Bore-wheat, a new hardy variety for the
cuhures of middle Sweden.

267

268 PLANT-BREEDING

grayish-yellow tinges, half a dozen of shades of brown, and
more of less completely black types may be distinguished.
Some of them have given proof of being suitable for some
regions and some uses, while others are preferable under
other conditions.

The spikelets may contain one, two, or three flowers, and
these numbers are dispersed on the different branches of
the panicle according to the special properties of the sorts
under consideration. Spikelets with two flowers are as a
rule preferable, since there is a near relation between this
number and the size of the kernels. In each spikelet the
flower of the undermost palet always gives the biggest kernel.
If it is the only one it may be smafl, but as soon as it becomes
accompanied by a second or a third flowering scale, its kernel
becomes heavier. In this way the many-flowered spikelets
do not only give more kernels but also bigger ones, and with
them all the advantages we have described of large seeds.
The size of the empty scales at the top of the axis of the
spikelet, the Httle hairs at the base of the palets, the more
or less twisted awns and their curvature give many mor-
phological marks, whose correlation with the breeding
qualities may be studied.

Corresponding marks are afforded by wheat, and rye,
and barley. Among them the number of the kernels in each
spikelet prevails, but the size and density of the whole ear,
the characters of the outer scales, and even their hairiness
may be advantageously compared. At the Swedish agri-
cultural experiment station, for each genus of cereals a system
of classification has been traced which gives a survey over
all these botanical marks and their relation to industrial
qualities. These relations of course have had to be studied
experimentally, and large cultures as well as exact measure-
ments and determinations of chemical value, baking and
brewing qualities and many others have been made. It

THE ASSOCIATION OF CHARACTERS 269

has taken years to arrive at a sufficient degree of knowledge
of all these correlations, and the investigations, though cov-
ering more than ten years, have as yet not nearly been
exhausted. But the general result has been that the indus-
trial worth of any individual plant can now be estimated by a
thorough inspection of its panicles or ears and with a degree
of certainty which is wholly sufficient for all purposes of
selection.

As an illustration of the high significance of these corre-
lations, I will now return to the example of the Primus-barley,
of wliich I spoke in a previous lecture. As already pointed
out, all endeavors to breed a race of Chevalier-barley with
stiff culms had led to no appreciable ameUoration, and
the cultures in this direction had to be given up. The
principle of correlation, however, pointed to another way
of solving the problem. Instead of trying to breed a Cheva-
lier-barley with rigid halms, a stiff variety was chosen, and
it was proposed to give to this the quahties of a fine brewer's
barley. In Sweden a kind of barley is largely cultivated
which bears the name of Imperial barley and belongs to
the subspecies of Hordeum erectum with stiff culms, hairy
scales, and coarse kernels. This variety, the good qualities
of which were duly appreciated, was taken for a starting-
point in order to produce the desired barley for the brewers.
The study of the correlations between morphological and
industrial features had led to the discovery of a coincidence
of some marks of the hairs on the base of the scales with the
composition of the albumen of the grains. Long and
straight ones are correlated with coarse kernels, but short
and crisp, more or less woolly hairs are indicative of those
quahties which stamp a barley as a good kind for the
brewery.

On the basis of this correlation, combined with the dis-
covery of the existence of innumerable individual variations, it

270 PLANT-BREEDING

was judged probable that among the resistant Imperial barley
some spare individuals might be found with compact kernels,
suitable for brewery purposes, and that they would be recog-
nizable by the form of the hairs of their scales. This con-
clusion led to a formal hunt for such specimens. Of course,
among some hundreds they could hardly be expected, but
in each thousand it might be possible to find a single one.
All the fields of the Imperial barley of the station were
scrupulously inspected, and any specimen with a diverging
type of hairiness was marked out. Many thousands of plants
with long and straight hairs had to be analyzed before the
desired ones could be found. At the end some sixty were
judged worthy of further trial. Their cars were collected
separately, and in the next season the progeny of each single
selected mother plant could be studied. The investigation
was now directly turned to the brewery quahties and taught
that in some thirty of the cultures the expected correlation
was really present.

This result crowned the labor of the previous summer,
as well as it gave proof of the reliabiUty of the principle in-
volved. It was quite sufficient for the practical aim of the
experiment. On the field plots of this second generation
eight new and valuable types could be discerned, each of
them evidently a fine brewer's barley with resistant halms.
They were quite as good as the ordinary cultivated ChevaHer
sorts, though not at all derived from them. Among them
all further care had to be directed to a rapid propagation,
and to comparative trials of the eight eUte strains. One
of them was found to be the best, and to comply with all
the demands of the brewers. It got the name of Primus-
barley, as already quoted. It was resistant even on the
hardest soils of Middle Sweden, but its kernels can scarcely
be distinguished from those of the best Chevalier varieties.
It is a brewery barley of the very first rank, on account of its

THE ASSOCIATION OF CHARACTERS 271

pale yellow color, its smooth and downy coat, its typical
form, and the chemical qualities of its tissues.

This new race has been constant and uniform from the
very first moment of the discovery of its mother plant. Its
progeny had only to be multiphed, absolutely no selection
being wanted. The multipHcation has been very rapid, and
nine years after its commencement (1892) it could be given
into trade (1901), having triumphed at numerous agricul-
tural expositions over all other similar sorts.

Apart from the enormous amount of work involved, as
well in the selection of the first year as in the consecutive
comparative trials of the originally isolated strains, this great
success is in the main due to the discovery of the laws of
variability and correlation governing the characters of our
cereals. It is a principle, which already has given proof
of its wide appHcabihty to nearly all the large agricultural
crops, embracing even the minor types, such as vetches and
other leguminous forage plants. It is a leading idea, and
hardly any Hmits seem to be set to its influence. To the
practical breeder it shows the way in nearly all the burning
questions, and for the scientist it may prove to give the
solution of numerous problems which have eluded his evo-
lutionary speculations for more than half a century.

C. A METHODICAL STUDY OF CORRELATIONS

Correlations between botanical marks and breeding qual-
ities are to be considered as rehable guides in the work of
selection. Numerous instances have been dealt with in
which single individuals, chosen in a field on account of
some sHght deviation of form, color, or hairiness, have
become the parents of valuable varieties. Until some years
ago our knowledge of these correlations was limited to a
greater or lesser number of isolated cases, and although
their significance was clear enough, it was hardly possible

272 PLANT-BREEDING

to point out the way in which further progress might be
attained.

At the Swedish agricultural experiment station of Svalof,
however, it soon became evident, that this principle might
some day become the basis of exact methodical work. The
fact once ascertained, that the fields of our ordinary crops
are by no means uniform, and moreover conceal a noticeable
number of excellent types, suitable for the most widely
different requirements, the need was instantly felt for a
method which would enable the breeder to make his selec-
tions as large and as profitable as possible. According to
the rules already explained, this choice must always be a
two-fold one. In the first place comes the work in the
ordinary fields, the picking out of the aberrant individuals
which seem to promise some special result. Thousands of
ears are inspected and tested, and on account of certain
marks those are chosen which do not comply with the main
type. Then their seeds are sown, and the progeny of each
single specimen is studied and compared with the already
cultivated varieties. This comparison depends in part on
the same marks as the initial choice and in part on the
direct control of the agricultural quahties. By means of
this latter the judgment is finally made independent of the
laws of correlation, which by this contrivance afford only
the means to reach the aim by a far shorter and easier
way than would be possible if the first choice itself had to
be made on the basis of exact measurements of the practical
value of the individual plants.

We thus see that we may hmit our study to the initial
choice. We may leave the subsequent work out of consider-
ation, since, as far as the correlations are concerned, they
require the appreciation of quite the same marks. But in
order to make the first choice as reHable and as profitable
as possible, a thorough knowledge is required. It must

Fig. 82. A panicle of oats with weak branches, photo-
graphed at Svalof, Sweden.

273

274 PLANT-BREEDING

include three subdivisions. These have to deal respectively
with the morphological marks, with the agricultural quahties,
and with the correlations between these two groups. The
agricultural quahties may be assumed to be manifest, but
the botanical pecuharities have hitherto been neglected, or
studied only in a superficial way, so far as their appreciation
was needed for the ordinary botanical systems.

These older systems were based on a very imperfect
knowledge of the real nature of the variability. No sowings
had been made in order to study this phenomenon, and it
was simply assumed that all minor pecuharities, in which tlie
single individuals of a species differed from one another,
were changeable and did change from one generation to the
next. On this assumption their intricate nature could hardly
be of any significance for the systematist, and was therefore
almost always neglected.

The discovery of the numerous elementary species, of
which the common varieties consist, has at once changed
the whole aspect of this question. Numerous apparently
insignificant marks proved constant in pure sowings. They
offered an easy and rehable means of distinguishing strains
of widely divergent practical value. Thence the conclusion
that they must be subjected to an exact study, which would
enable the breeder to discover any new and useful type that
might occur in his fields.

In order to do tliis, a thorough study had to be carried
on for a number of years. The single characters had to be
classified, so as to give distinct systems. In these, each
botanical mark may be indicated in combination with its
correlative significance. By this means, whenever a distinct
practical quality is wanted, the correlated botanical marks
may be looked up in the system.

Such elaborate systematic surveys have been pubhshcd
from time to time by the experimenters of the staff of Svalof.

Fig. 83. A panicle of oats with stiff branches, photographed at Svalof,

Sweden.

27s

276 PLANT-BREEDING

They include the cereals, the peas, some leguminous forage
crops, and a small number of other agricultural plants. As
an instance, I choose the system of the wheat. It embraces
seven divisions, which are indicated by the name of types.
They are distinguished by the qualities of the ear which may
be long or short, tight or brittle, and densely or loosely cov-
ered by the spikelets. In the first place comes the widely
known type of the Squarehead with its butt-ended ears.
From this are derived varieties with ovate ears, whose broad-
est part is seen in the middle. CyHndrical ears arc of the
same breadth throughout their whole length, but in one type
they are almost square and in another more or less flattened.

These types are further subdivided, according to other
marks, each of them embracing some four or five groups
of minor value. They are distinguished by the color, size
and form of the grains, the marks of the scales, the occur-
rence or absence of awns and other similar marks. All
these seemingly insignificant characters have been shown to
be constant in the pedigree cultures, and an exact study
of them enables the breeder to recognize each single type.
So it is also with the minor marks, by which the single kinds
are finally distinguished. Often these are almost invisible
to the inexperienced eye, and years of persevering study are
necessary to obtain the faculty of recognizing them easily
and rapidly.

With this object in view a division of labor has been
established, finely adjusted instruments for measurements
and comparison have been invented, and large collections
of samples and pictures have been brought together. Each
of these points now demands our special attention.

Division of labor has been the first requirement, the study
being so extensive that it was impossible to take more than
one agricultural species into consideration at a time.
The panicle of the oats, which was described in our last

THE ASSOCIATION OF CHARACTERS 277

chapter, afforded the most promising instance, and was
studied first. Soon afterward other cereals and peas were
treated in the same manner, then vetches, but most of the
other agricuhural crops have been taken into consideration
only during the most recent years, or are still awaiting at-
tention. Gradually many hundreds of definite forms were
distinguished witliin each species, and the amount of work
became so large that it was necessary to divide the subject
among several investigators. Neither the time nor the
memory of one man was sufficient to embrace the whole
realm of the botanical marks and of their correlations to
breeding quahties for all the elementary forms of more
than one or two species. And perhaps just this statement
is the best way in which to convey to the layman an idea of
the enormous amount of work that is involved in this study,
and required for the complete exploration of all the single
forms, now growing mingled together in the fields.

At Svalof the director Dr. Nilsson has chosen for his
own department, the cereals and especially the oats, and is
assisted in this work by Mr. Nilsson-Ehle. The leguminous
crops, such as peas and vetches, are the department of Dr.
Tedin. Rye has been studied by Mr. Wallden and potatoes
by Mr. Lundberg. Other special crops have been given
into the hands of Mr. Elofson and Mr. Witt. Each of
them has become a specialist in his line and has acquired
a high degree of abihty in singling out the rare promising
individuals from among the thousands of ordinary specimens,
which commonly constitute the majority of the ordinary
varieties. An instance of this v/ork was described in our
last chapter, in the production of a brewer's barley with
stiff culms. By such means it becomes possible to estimate
the probable agricultural value of all aberrant individuals.
Whenever a distinct quality is desired, either in order to
improve a local variety, or to bring it into a form suited for

278

PLANT-BREEDING

other conditions of soil or climate, or to comply with any
other wishes of agricultural practice, it is necessary only
to know the botanical marks correlated with the desired
qualities. On this basis individual plants may be singled
out, and after multipUcation through a few years, their
progeny will probably respond to the demands made, as
soon as the industrial quahtics themselves are investigated.

Fig. 84. A. Spikelct of oat-grass {Avena elatior), showing a flower with
two palets, three stamens, and two stigmas (a), a flower bud (b), of
which only the palets are visible and the third or sterile flower (c).

Some instances of correlations may now be presented.
Different elementary species of oats are distinguished by the
form of their panicles. Some are stiff with a firm principal
axis and erect branches. In others the axis is weak and the
branches droop. In some varieties they are widely spread,
but in others they all bend to one side. According to these
marks definite types have been distinguished, and in com-

THE ASSOCIATION OF CHARACTERS

279

paring these with the industrial value of the varieties it has
been discovered that stiff and erect main branches building
a dense tip on the panicle are indicative of the richest har-
vest and of the best kind of kernels. Varieties with loose
flexuous branches are usually only poor yielders. The

Fig. 85. Barley. A. A complete spikelet with the three flowers. B
and C. Single flowers seen from different sides, showing two palets, three
stamens, and the ovary with the stigmas. In B also the two outer scales
orglumse with the stigmas. D. Stamens and ovary of a flower.

number of the grains in the single spikelets affords another
instance. It is correlated by distinct laws to the size of the
kernels, and through this mark to the industrial value of the
variety. Moreover these numbers are strictly hereditary and
so give very reliable marks. Oats and wheat especially

28o PLANT-BREEDING

have been studied from this point of view. In barley, one of
the main characters and one which has been already alluded
to is found in the hairiness of the scales, bristles, and other
parts of the spikelets and flowers. In some cases the hairs
are smooth and pressed against the scales, in others they
are stiff and spreading. Crisp and woolly hairs arc, as a
rule, to be considered as indicating the most valuable types.
Experience has taught that in this simple way it is possible
to select in each variety the elementary form that will prob-
ably be the best yielder. The midveins of the outer scales
afford still further marks. In some cases they are smooth,
in others armed with small but sharp teeth. Even these
differences are constant in pure cultures, and indicative of
correlated yiclchng quahties.

The same laws of correlation have been observed with
other agricultural plants. Prominent amongst all are the
forage crops of the large family of the leguminous plants.
Here the differences between the numerous elementary
forms within the botanical species are not so very small
and so difficult to realize as in the cereals. Peas and vetches
have been studied in the first place, but clovers, wild species
of sweet-peas, and several other forms, whose culture had as
yet hardly been profitable, have also afforded notable results.
For peas the correlations have been studied by Mr. Tedin,
who has published liis results in tables, giving the average
weight of the seeds, their number in the pods, and their
total number on the individual plants, in combination with
other valuable qualities. On the ground of this system he
has been able to distinguish 500 different kinds of peas,
which have proven constant in his pedigree cultures, and
among which some 40 could be selected as evidently ex-
celHng the ordinary varieties out of wliich they had been
isolated.

In the same way some 75 new and constant types of

Fig. 86. Svalof Solo pea, a new forage-plant, most pro-
ductive of seeds and foliage. Leaves green.
281

282 PLANT-BREEDING

vetches have been isolated at Svalof, In some of them the
flowers are white, in others pink, instead of being purpHsh,
as in the ordinary sorts. The seeds may be spotted or not,
of a dark or of a pale hue. The spots are small, isolated, and
rounded in some varieties, but in others they radiate from
the hilum Hke tongues of flame. Minor marks are aiTorded
by the size and shape of the leaves, the length and mode of
branching of the stems, the distribution of the pods along
the branches, and so forth. All these marks are constant,
as soon as cultures are made, each starting from a single
parent plant. An elaborate system of the vetches has been
derived from them, and the single types are now being cul-
tivated separately, in order to examine their industrial
value.

Similar investigations have been made for clover. The
Spanish or red clover was formerly imported into Sweden
where the first work has been the controlling of the value
of introduced sorts and of their fitness for the Swedish
chmates. American sorts of clover proved too susceptible to
the hardships of the Swedish winters, but many of the kinds
of Middle Europe were resistant enough to be cultivated with
success. The red clover is very variable, in respect to the
shape, and size, and color-designs of its leaves, as well as to
the flowers and flowerheads and especially in the colors
and qualities of the seeds. A great number of types could
easily be isolated. This richness in forms and the constancy
of the isolated types had already been studied in several
other countries, as, for instance, by Schribaux in Paris, and
by Martinet in Geneva, and their different commercial value
had clearly been pointed out. But by means of the method-
ical study of the botanical characters, which is the principle
of the work at Svalof, a far larger number of types could
be isolated and varieties be originated which comphed with
all the divergent demands of the soils and climates through-

Fig. 87. Svalof Grop pea, a new early ripening forage-
plant.

283

284 PLANT-BREEDING

out Sweden. Similar results have been obtained with the
white and the crimson clover.

Many other species of leguminous plants are available
for the culture of green fodder. Different kinds of lucerne,
of which the alfalfa is the best known species, som.e forms
of Lathyrus, and others have been included in the tests.
They are rich in elementary types, but even of the botanical
species the agricultural significance was hardly known.
Some instances may here be given. Lathyrus heterophyllus
is an early ripening species, with sweet tissues and a vig-
orous growth. It is an excellent yielder. Lathyrus praten-
sis and Vicia Cracca, two common species along road sides
in Europe, recommend themselves by their fitness for mixed
cultures on meadows. A richer type of Lotus uliginosus
with broader leaves and a resistant variety of Lathyrus
sylvestris have been isolated.

Potatoes, beets, and even the ordinary meadow-grasses
have been subjected at Svalof to the same methodical study.
It would take too long to give all the details. It may suffice
to choose the grasses as a last instance. On meadows, the
vegetation is a more or less mixed and motley array of nu-
merous types, belonging partly to the grasses and the legu-
minous family, partly to other less valuable or even obnoxious
species. The value of the different kinds of grasses depends
mainly upon the question whether they are at their fullest
development at the time when the hay is cut. Some species
are too early, become woody, and lose their nutrient quaHties
before the harvest. Others are too late, and have only pro-
duced part of their foUage at that time. Both, of course,
constitute a distinct loss, and it must be considered a chief
aim in the improvement of meadows to replace them by
types which will ripen simultaneously.

Now the experiments at Svalof, although as yet only
few in number, have shown that the ordinary grasses are

Fig. 88. The wild oat-grass {Avena elatior), a
pasture grass.

285

286 PLANT-BREEDING

at least as rich in elementary species as the cereals. These
minor types can be distinguished by botanical marks which
are correlated to the time of ripening and to their yielding
qualities. Especially variable are the common Avena ela-
tior and the different species of Agrostis. The first of them
gave 14 distinct forms in the first trial, and later tliis number
was increased to about 50.

In concluding this hasty survey of the results of the
methodical study of correlations at Svalof, I might emphasize
the great principle of the combination of the scientific and
the practical sides of the question. Selection on the ground
of practically valuable quaHties only, has been the rule until
very recently. Of course it was a good and reliable method,
but it was extremely limited in its application; on the other
hand, the whole history of the breeding process in Germany
consists of isolated cases. No doubt these have yielded
very valuable results, but the Svalof principle gets rid of
the incumbrances to a more universal use. By it the
breeder is enabled to single out hundreds of valuable strains,
and to select among them the very best. The search in the
field is made on the basis of marks which can be recognized
instantly by the experienced eye, upon a simple inspection of
the ears and panicles, of the stems and their branching, and
of the shape and size of the leaves. Thus the purely mor-
phological distinctions take the place of the agricultural
tests, which embrace measurements and estimates, that can
hardly be made for single individuals and never can be ap-
plied to so large numbers of specimens as can be compared
by purely scientific marks. A broad scientific foundation is
thus seen to be the means of abridging the practical work
and this to such a degree that the selection may be extended
and appHed to almost all the requirements of practice at
large.

Two essential features of the selection work at . Svalof

THE ASSOCIATION OF CHARACTERS 287

are still to be dealt with. A short description must be given
of some of the new instruments for measurement and com-
parison, and the collections of samples and pictures of select-
ed plants must be mentioned. In the hst of apparatus the
"classificators" may be described in the first place. This
name is given to small collections of say 15 to 40 ears arranged
according to a definite character. For each quality a special
classificator is at hand, so for instance, for the size, the shape
and the density of the ears. In order to classify an ear
it is shoved along the row, until it falls between two ears
of the classificator, one beyond and the other behind it.
The intervals between every two succeeding ears of the
apparatus being marked by figures, the figure on which
the ear falls is the indicator of its degree of the character in
question.

The transparency of the grains of barley is measured
by means of screens with holes. These are exactly filled
by one grain each, and the standard-kernels are arranged
according to the degree of their diaphaneity. The grains
to be tested are put into similar holes of a Httle separate
screen, which can be shoved along the classificator until
their transparency coincides with that of one of the standard
types. The degree of mealiness is tested by a small pincer
which measures the pressure required to squeeze the ker-
nels into pieces. Other instruments are so constructed that
they collect from an ear or a panicle all the lowest grains,
all those of the second rank and so on, in order to determine
the average weight of each group separately. As we have
seen, the seat of the heaviest kernels is one of the important
marks in the testing of varieties of cereals. Many other
instruments have been devised in order to make the esti-
mates as independent of personal impressions as possible,
and thus to make them thoroughly reliable even if they
have been made in different years or in different localities.

288 PLANT-BREEDING

From these short descriptions it is easily seen that one
of the aims of the method of selection is the grading of all
marks in figures. By this means it becomes possible to
give extensive comparative surveys of whole groups of newly
selected plants or of the strains derived from them and to
draw a parallel between the new and the already existing
varieties. Without it the testing of the value of many
hundreds of new types would evidently be scarcely possible.

With the same object in view larger collections have
been made and separate buildings have been erected in
order to exhibit them in such a way that they are easily
accessible whenever a new form must be compared with the
older types. For the testing is by no means limited to the
ears and the kernels, but embraces the whole plant, during
the several periods of its development. Dried spec-
imens of seedhngs must be at hand for all of the useful varie-
ties. The manner in which the culms produce their more
or less numerous side halms must be illustrated, also the
length and the stiffness of the straw, on which nearly the
whole value of some varieties depends. Moreover the varie-
ties are not only to be compared with one another, but their
constancy must be tested, and for this purpose some spec-
imens of previous years must be preserved. In this way
pedigrees of dry specimens have been built up, which convey
to the visitor an idea of the whole previous history of the
race, and contain, besides the proofs of its constancy, the
indications of any deviation, which may have occurred in it.

These collections are to be considered as li\ing expres-
sions of the systems described before. The investigator
visits them with the plant he wishes to classify, and is guided
by their arrangement so that he may find the corresponding
prototype in the easiest way. They have this great advantage
over the printed systems that all the single quaHties may
be taken into consideration at once, without the labo-

THE ASSOCIATION OF CHARACTERS 289

rious comparison of the figures in the tables. It is almost
superfluous to mention that the collections are largely
illustrated by drawings and photographs, and that charts
giving the results of the tables in a statistical way facihtate
the work. Pedigrees have been drawn for most of the
important novelties of the station.

The work of Dr. Nilsson and his staff at the Swedish
agricultural experiment station at Svalof is a model of the
combination of science and practice. The problems it has
to solve are purely practical ones, but the method depends
upon exact scientific studies. The station is a private
enterprise, founded by the Swedish agriculturists for their
own direct use; it has neither to serve educational aims,
nor to yield results of theoretical significance. No purely
scientific researches are carried on, no grouping of results
with the sole object of contributing toward the solution of
biological problems is allowed. But its experience has
taught the indispensableness of scientific principles and
methods. Only under their guidance may the practical
work be kept within limits which guard it against useless
and superfluous experiments, and which cause it to attain
its purpose by the shortest and most direct way. This
method of applying science to practice has opened previously
unsuspected possibiUties and discovered new fields of in-
vestigation in the study of the highly interesting relations
between botanical marks and quahties of practical value.
It will soon bear fruit for the doctrine of evolution and for
the theory of specific units in addition to its conspicuous
results for agricultural practice.

D. CORRELATIONS IN FLUCTUATING VARIABILITY
Correlation is the name given to regular coincidences of
apparently independent characters and marks. This reg-
ularity is not meant to be absolute; it simply means the more

290 PLANT-BREEDING

or less frequent occurrence of the observed combinations.
On the other hand the conception does not exclude cases of
complete mutual dependency of characters; it is even prob-
able that it embraces many of them, but that our knowledge
is still too incomplete to allow us to draw a distinction be-
tween these and the ordinary cases. The other extreme in
the long list of possible combinations is evidently given by
casual and fortuitous coincidences, accidentally repeated
in some group of observations. A continued investigation
would show these to have no real value, and so they may
here be left out of consideration.

After our hasty survey of some of the most interesting
facts, we may now proceed to inquire into their causes.
These may be brought under two heads. The causes may
be internal or external. In other words the correlation may
depend on some inner connection of the qualities, or simply
on corresponding changes induced by environmental in-
fluences. Evidently, the internal correlations are the most
interesting, and moreover those which may be the most
completely rehed upon. Outer Hfe-conditions, working in
the same direction on different characters, on the other hand,
are more easily understood and more directly accessible for
experimental study. On this account a rational treatment
will have to begin with the latter, and discuss the former
or internal causes of correlation only after the field has been
cleared as much as possible of its foreign elements.

For tills reason I have chosen for this chapter the study
of the influence of external life-conditions on the phenomena
of correlation.

Correlated variabihty is quite an ordinary feature in all
plant life. It may be seen almost everywhere. As soon as
a plant deviates from its type, it will be disposed to do so in
more than one character. This rule holds good for rare and
casual abnormahties, as well as for the more normal, so-

Fig. 89. A pitcher-like leaf of tobacco.

291

292 PLANT-BREEDING

called fluctuating deviations from the type. Useful qualities
are subjected to it as well as those practically useless marks,
which are usually studied merely on account of the valuable
indications they so often give for comparative science.

Some of our most convincing arguments may be derived
from the study of tcratological phenomena. Every one
who is collecting monstrosities, knows that they are, to a
high degree, dependent on the influence of the environment.
Some years are known to be rich, and others poor in abnor-
mal developments. One of the most notable instances is
the year 185 1, in the summer of which pitcher-hke leaves
appeared in such large numbers, as to be regarded as a dis-
tinct disease. This was the case in the western districts
of Belgium, and wliile roses and other plants were notably
affected, the damage done to the tobacco cultures was re-
ported to be quite heavy. In Baden the summer of 1886
and around Paris the fall of 1893 are described as exception-
ally rich in abnormal productions, and other instances could
easily be given. Evidently some external cause was at
work, and high temperature and moisture are among the
factors called upon by different authors to explain the fact
which so deeplv impressed them.

In a single locahty the same phenomenon may often be
observed. Some hillslopes and some fields are productive of
monstrosities, while others are not. By this means a bota-
nist is often enabled to discover the locahties, which may
give him the deviations he wishes to collect. Sometimes it is
one species which offers a profusion of interesting instances;
in other cases a more or less large number of plants are
included in the phenomenon. This observation is often
stated by saying that a monstrosity is seldom seen alone;
it is quite generally accompanied by others.

Some instances may be given as proofs. Pitchers are
ordinarily built out of one leaf, or of some part cf it, but

THE ASSOCIATION OF CHARACTERS

293

together with them two-bladed pitchers may not rarely be
observed, as in the magnolia and the common plantain.
The pelories of the foxgloves are almost always -the seat of
secondary deviations, such as tube-hke petals, fissions of the
corolla, multiplication of the stamens, the production of a
secondary raceme from within the capsule, and so on. Even

Fig. 90. Pitchers of Magnolia, A, B, C. Of clover, D, E. Of the

lime tree (Tilia), F, G, One-leaved pitchers. C. Two-leaved. A. Upper

part of a leaf only transformed into a pitcher. D, E. Pitcher-like leaflets of
the ordinary and of the five-leaved clover.

the beautiful erect peloria of our cultivated Gloxinias often
show deviations from the normal number of tips of the
corolla and of stamens. Fasciations are usually combined
with cleft leaves and other alhed monstrosities, and twisted
stems are so rich in their deviations as to afford sufficient
material for quite a large field in the science of teratology.

294 PLANT-BREEDING

On this principle of correlation a definite method of
searching for monstrosities has been founded. Years ago
I was impressed by the fact that deviations in the seedUng
plants are often followed by abnormahties in the adult
state. By this means, the cotyledons of the seedlings may
give indications of what is to be expected. Now it is as
easy to inspect thousands of germinating plantlets as it is
difficult to cultivate the same number to their full develop-
ment. But by choosing the stray seedHngs with three
seed-leaves or with connate cotyledons, the cultures may be
effectively reduced, the chance of producing monstrosities
on a given space being proportionately increased.

Leaving the abnormal characters, we have now to con-
sider a group of observed cases of correlations in ordinary
deviations. I choose my instances from among the agri-
cultural plants. Fruwirth has studied the relations in
the development of leguminous crops, at the agricultural
station of Hohenheim in VVurtemberg. He observed a
parallelism between the increase of the total harvest and the
weight of the pods, the number and the weight of the seeds.
Less intimately, but still clearly correlated with these char-
acters was the average size of the seeds and the average
height of the whole plants. Gwallig observed that large
kernels are as a rule richer in albuminous substances
than small ones. This relation has been found to hold
good especially for peas and lupines, both belonging to the
same family and often cultivated as forage crops.

Flax has been studied in this respect by Schindler, who
stated that the length of the fibers and their total amount
are correlated with the total height of the plant, measured
from the root to the highest capsule. The thickness of the
stem is inversely correlated with its height, higher plants
having thinner stems. Therefore, for the harvest of the
fibers the thinner specimens and strains should be preferred.

Fig. 91. A. Seedling-plants of Evening Primroses. B. Of the figwort
{Scrophnlaria nodosa). C. Of Silene odontipetala. D. Of poppies. E.
Of the beech. A i and D i normal seedlings. A 7, B, C 2, D 4, E,
Tricotyledonous seedlings. C 3, D 5, Seedlings -svith four and D 6 with
five seed-leaves. A 2-6, C i, D 2-3. Different degrees of splitting of
seed-leaves.

295

296 PLANT-BREEDING

Tall plants are less branched than smaller ones, and bear
a correspondingly smaller number of capsules and of seeds.
Potatoes have often been an object for comparative measure-
ments of their different parts and a survey of their correlations
shows that these are quite numerous. It may suffice to
merely point out the paralleHsm between the average number
and weight of the tubers on a plant, the number of stems,
and the amount of starch in the potatoes.

Many other instances could be given. They all give
proof of a high degree of parallelism between the different
organs of a plant, increasing development of one cjuaHty
being combined with increase or decrease of other points
according to definite rules. By this means selection may
be guided, as we have seen in a previous chapter. But the
cultural treatment may be furthered also by the observation
of such correlations, because in stimulating the develop-
ment of some parts we may expect to increase the size or
weight of others at the same time. An exact knowledge
of these phenomena is thus of paramount interest for agri-
cultural practice, and the difticult and tedious study of all
its features should be dihgently carried through until definite
principles for the practical work may be derived from it.

Inquiring into the causes of the parallelism of apparently
independent characters, we have first to state that it is often
difficult to decide whether the observed combinations are
due to internal or to external causes. Among the facts
I have quoted, there' can be no doubt that at least a large
majority are due to external influences. On the other hand,
more intimate or internal relations may be hidden in some
instances without our being able to discern them and thus
to classify our group of phenomena. Our only way is to
leave them out of consideration until further investigation
will have pointed them out and to consider our facts as
uniform and as the result of the same causes.

THE ASSOCIATION OF CHARACTERS 297

External influences can affect a plant only because of
some kind of responsiveness which must be present in it.
Without such no reaction will be produced. This assertion
may seem to be a truism, but even as such it m.ay help us
to reach a better view of the relation under discussion.
For it is clear that a parallel action of the external factors
demands a corresponding response of the cliaracters to them,
and we may base our discussion upon this assumption,
making the state of sensibility its chief aim.

As a rule, all variable parts are influenced by the same
factors. Among them the nutritive are most prominent.
Other agents, such as temperature, moisture, and light,
cooperate with these in a more or less considerable degree.
Many authors, however, take their significance to be only
secondary, inasmuch as the nourishment itself may be
changed by them. On the basis of this conception, nutrition
would be the main factor in all fluctuating variabiHty.

Now it is evident, that all development depends in the
first place upon the amount of available food. This simple
sentence gives a key to at least a large group of the phe-
nomena of correlation. Whenever the size of the seeds
increases with the weight of the whole harvest, or the number
of seeds in a pod with the height and degree of branching of
the plant, there can be no doubt that all these qualities
depend upon the nourishment, and that it is this factor
which causes them all to increase or to decrease at the same
lime.

This rule will be more easily understood if we take a
definite example. As such I choose a variety of cultivated
poppies, belonging to the ordinary tall species or opium-
poppy (Papaver somniferum). Numerous forms of this
beautiful plant are cultivated in our gardens. The most
pecuhar among them is the variety in which the stamens
are partly converted into pistils. These secondary pistils

298 PLANT-BREEDING

surround the capsule by a large crown of slender and green
organs, which persist after the petals and stamens are
fallen off, and thus heighten the ornamental effect of the
fruits. Only the innermost rows of stamens are changed
in this way. Both the filament and the anther are affected,
the former being dilated into a sheath, in whose cavity the
ovules are produced. Ordinarily these latter are only
imperfectly developed and the bright crown of secondary
pistils contribute Httle if any to the fertiHty of the flower.

What makes this variety especially suitable for our dis-
cussion is the high degree of variabihty in the development
of this crown of pistillodous stamens. In some instances
it is seen to be so broad as to have affected a large majority
of the stamens; in others only one or two of these parts are
changed, and in extreme cases only a single hardened and
persisting filament without an ovarial cavity and without
stigma indicates the type. All intermediate forms may be
found and the variabihty covers a range, going from one
pistil up to a hundred and fifty and sometimes even more.
Unfortunately these altered organs often show another
anomaly, consisting in a coalescence of some of them, thereby
constituting groups, in which it is difficuk to distinguish and
count the single parts. In extreme cases this coalescence
may be such as to combine all the changed stamens into a
narrow cup around the normal capsule, and more com-
monly a more or less divided ring of such groups is observed.
It is easily seen that the variabihty of this character affords
an excellent material for the study of its dependency on
outer influences. We may make sowings under different
circumstances, giving them a sunny or a shaded place, good
or bad soil, different quahties of manure, watering or keep-
ing them dry, protecting the young plants under glass or
exposing them to all the effects of the weather, and so on.
If we do so we easily find that all favorable conditions

Fig. 92. Polyccphalous opium poppy. A. Normal fruit. B. The same
cut longitudinally. C, D. Normal stamens. E, F. Stamens transformed
into secondary carpels. G, H, I. Secondary carpels, cut transversely with
one, two, and four rows of seeds.

299

300 PLANT-BREEDING

increase the crown of pistillodous stamens, while adverse
influences reduce the change and thus favor the production
of the normal organs.

The same influences, however, govern the degree of
development of the whole plant, the height and the thickness
of the stem, the size of the flower and the fruit, the number
and the strength of the branches, and even the extent of the
fohage. Hence we may expect a correlation between the
abnormahty and the growth of all the normal parts, and it is
quite easy to control this. The best means is to choose the
ripe capsules. Their size and weight is evidently the result
of the activity of the whole plant, during the whole time
of its Ufe, and thus may be considered as a standard for
comparison.

In a bed of pistillodous poppies, we pick out a group
of fullgrown fruits and arrange them according to their
size, taking as a measure either the height or the weight of
the central capsule without the crown of secondary organs.
Then we compare the degree of development of the anomaly
with this size, and we find an almost complete parallchsm.
The smallest fruits are devoid of appencUxcs or nearly so,
and the largest ones bear the richest crowns. Between
these extremes the number of the altered stamens regularlv
increases with the size of the fruit, hardly any deviation
from the most complete parallchsm occurring.

By this investigation the normal and the abnormal
development are proven to be as closely correlated as might
be expected. So it is also in other instances. Ordinarily,
of course, abnormahties are too rare to permit of such a
complete comparison, but notwithstanding this, common
experience shows them to be connected with strong growih
and favorable Hfe conditions. This relation is often so
striking that in former times it was simply assumed that
monstrosities could be produced by an excess of nourishment,

Fig. 93. Young plant of opium poppy in the sensitive period of the
development of the terminal flower, cut longitudinally. A. Flower-head of
June, 7. B. June, 14. C. All parts discernible. D. Diagram of flower.
E. Diagram of young flowerbud. P. Petals. S. Stamens.

301

302 PLANT-BREEDING

but at present it is known that the faculty of producing them
must be present beforehand, and that the food-supply can
only stimulate the frequency of occurrence and the degree
of development.

We may now proceed one step farther and inquire into
the time at which the external influences can affect the size
and the form of the organs. It is evident that these agencies
must be Hmited to the period of youth, because as soon as
the growth ceases, no further change is possible. Here,
however, the form and the size must be considered separately,
the form being definitely fixed long before the size of the
organ is determined. We thus come to this conception
in regard to periods of scnsibihty, that the one for the form
ceases earlier than that of the ultimate increase.

The pistillodous opium-poppy may once more be chosen
as an example. If we examine a young plant six or seven
weeks old we find a short stem bearing a group of leaves
which surpass it in size many times. The young bud of
the flower is attached at the head of the stem. Its calyx
covers the innermost parts, which are still very small. The
central capsule hardly begins to be differentiated and the
whorl of stamens is seen as a smooth wall of soft tissue
around it. At this period the normal and the pistillodous
stamens are still awaiting the first manifestation of their
form. Shortly afterward they may be seen as small protuber-
ances, rounded and without distinct form, but gradually
increasing and assuming more definite types. At this time
there is still no visible distinction between the normal and
the pistillodous stamens, and it is not possible to decide
whether the. bud would grow into a rich or into a poor
representative of the variety. A few days afterwards,
however, the decision becomes apparent, and the period
of sensibilitv closes.

Exact Hmits for this period of sensibility to the external

Fig. 94. The double corn-marigold, an experimentally produced variety.

303

304 PLANT-BREEDING

life-conditions cannot, of course, be set from these observa-
tions. But we do not need them for our present discussion.
The main fact is that all organs and qualities must go through
such a responsive period, and that this period coincides,
•at least partly, with their extreme youth. Hence we may
derive a general rule for the correlations depending on
fluctuating variabinty. For it is evident that, with the
continuous change of the weather, only such organs are
really exposed to the same life-conditions, as are sensible
to them at the same time. As soon as the period of sensi-
bihty has passed, the weather can no longer have an influence,
but new parts are produced which will be exposed to the
influences prevailing at that time. In this way we may
conclude that one of the great factors of correlation is
equahty of age, because it exposes the organs, during the
period of their sensibiUty, to the same conditions.

Another cause of correlation may be looked for in the
mutual dependency of different organs, the one affording
or controlhng the nourishment for the other. This case,
however, though of quite common occurrence, cannot always
be easily separated from the first, both causes ordinarily
combining their efforts in the same direction.

It may be studied by the statistical method. A hundred
or more individuals are measured, and the result is represented
by a single Hne. In order to do this, the individuals are
arranged according to the degree of development of the
measured quahty. Suppose we compare the amount of sugar
in the sugar-beets of a field. This amount can be measured
for a part of the tissue, without sacrificing the beet, allowing
thereby the selection and the ulterior cultivation of the best
samples. As is generally known the sap is pressed from
the tissue and after clearing it, the percentage of sugar is
determined by the method of polarization. In the year
1896, I had an opportunity of studying these percentage

Fig. 95. Variability in the size of the ripe fruits of the Evening Prim-
rose of Lamarck. A. A weak plant with small fruits. B. A tall plant with
large fruits^

305

3o6 PLANT-BREEDING

figures for some 40,000 beets, cultivated on the fields of
Messrs. Kuhn & Co., at Naarden, in Holland, and examined
in their laboratory for purposes of selection. The average
percentage was 15.5, the extremes going up to 19 and coming
dov^n to about 12 per cent. These extremes, however,
were comparatively very rare, especially on the upper side
of the group, where only a few individuals reached the very
Hmit. More than one half of all the beets differed less than
one-half per cent from the average, the total number of
roots with 15 to 16 percent sugar being about twenty-two
thousand. On both sides of this central group the number
of beets rapidly decreased with the increasing degree of
deviation from the average value.

In the same manner the fluctuating variability of other
quahties and other characters may be given under the form
of a curve. The ray-florets on the heads of the composites
can easily be counted for hundreds and even for thousands
of single flower-heads, and the figures thus obtained will
show a similar grouping around an average number. In the
marigolds this number is 13, in the daisies 21, and the same
figures are met with on the flower-heads of numerous other
species. The size of fruits and capsules may be treated
in the same way. I measured the capsules of over five
hundred incUviduals of an evening primrose and got a curve
that did not differ essentially from that of the sugar beets
just mentioned. The average individuals bore capsules of
nearly 2.5 cm. and the extremes reached 1.5 and 3.4 cm.
The largest capsules were thus seen to have about double
the size of the smallest ones. Between these limits the
different sizes were grouped in such a way that more than
half of the individuals could be said to have fruits of medium
size, the remaining sizes being respectively rarer the more
they differed from the average.

If now we compare this size of the capsules of the evening

THE ASSOCIATION OF CHARACTERS 307

primroses with the remaining qualities of the plants, we
observe a definite case of correlation. Small capsules are the
product of weak stems, long ones are borne only by stout
individuals. A curve, made for the height of the plants
would run nearly parallel to that of the capsules. Com-
paring weak branches with the main spike, we find the same
arrangements, the capsules on the former being decidedly
smaller. I have made some cultures with this species in
order to study the correlation of the capsules and the general
degree of development under the influence of different
outer conditions of hfe. By giving more manure, a better
exposure, or more adequate treatment, it is easy to get much
stouter stems, with a richer system of branches and increased
foliage. Along with these marks the capsules are seen
to increase in size, their medium length coming up from
2.5 to 3.5 cm. and their maximum reaching even 4.5 cm.

It is evident that the growth of the capsules in part
runs parallel with that of the other organs of the plant,
and in part depends upon them. A stouter stem, with
larger and more numerous leaves, produces more nourish-
ment for the flowers and fruits and thereby will make them
bigger. On the other hand, the tall individuals are largely
those which have found, from their very youth, the most
favorable conditions of soil, of water, of exposure, and of
other influences, and inasmuch as these factors are still
at work during the responsive period of the development
of the fruits, they will directly affect them in the same
direction. Thus we see that in such cases the causes of
correlation are twofold, the one acting directly, the other
indirectly, and influencing the younger organs through the
degree of development of the older ones.

Returning to the sugar beets, we may give our attention
to the correlations which the two main points in their life
may exhibit with the more easily appreciated characters

3o8 PLANT-BREEDING

of the roots and of the foliage. One of these two main
points, of course, is the percentage of sugar in the sap. The
other point is the quahty of the seeds, since on this quality
the harvest of the next year chiefly depends. Now it is
evident that of our two groups of causes which determine
the phenomena of correlation of fluctuating variability, only
the second one comes into consideration. This correlation
may be simply stated by saying that, as a rule, stouter plants
will be richer in sugar and produce better seeds. Nearly
all other causes, however, which govern the amount of sugar
in the roots of the first year will be without influence on the
quality of the seeds. Local variations in soil, in moisture,
and especially in the amount of space, when this is increased
on account of the falUng out of some neighbor, will directly
influence the sugar percentage, which may also be dimin-
ished by insects feeding on the leaves or by other diseases.
In the second year the roots will be planted in other fields
and with other conditions of soil and exposure, and during
the time of production of seeds the single individuals will
occupy quite different places on the curve of variability than
those they held the first year.

Hence we may conclude that the correlation between the
percentage figure for the root of the first year, and the real
value of the seeds is only a very feeble relation. The richest
roots may yield only poor seeds and conversely. In other
words, the percentage figures, which are now the universally
accepted criterion for the selection of beets for the produc-
tion of seed, are only an imperfect indication of the quality
of the latter. Direct experiments have often shown the
accuracy of this conclusion, and the breeders of sugar-beets
know very well that single excellent roots may not be relied
upon at all for the production of exceptionally good seed.
They rely only on the average of the selected beets, and
rightly assume that the larger the group of their roots, the

THE ASSOCIATION OF CHARACTERS 309

better is the chance that their seeds will be of superior qual-
ity. Selection of seed-bearers based on a direct measure-
ment of their average progeny, as it was originally appUed
by Vilmorin, seems at the present time to be too troublesome
for practice, though theoretically it would be much less open
to criticism, and though in the long run it would also yield
better practical results.

Such are the laws, which govern that most comphcated
phenomenon of the correlated dependency of characters and
qualities on the outer conditions of Hfe.

E. UNIT-CHARACTERS

The mechanism of an organism consists of numerous
parts which are more or less exactly fitted to one another.
Nearly all of them are dependent on some others in their
development, some profiting by the preponderance of these
and others being restricted thereby. Moreover they are
governed by the outer conditions of hfe and these influences
change some of them in the same direction and others in an
opposite one. Thus we come to the conception of a general
interdependency of all parts, organs, and quahties of an
organism. They are governed more or less by the same
laws which cause them to undergo corresponcUng changes
when subjected to the same influences.

In practice, this interdependency permits the indication
of valuable quahties by purely botanical marks, and gives
the possibihty of basing selection upon marks which may
be controUed in thousands of individuals without sacrificing
them and without the need of testing all of them directly by
their economic value. It is an important principle in plant-
breeding, which makes the work more rehable and more
available to horticulturists and agriculturists in general. Our
great admiration for men of genius may not prevent us from
deploring that the improving of our domestic animals and

3IO PLANT-BREEDING

plants should be laid in their hands only. We wish to know
how they work, and how their great achievements are
obtained. We wish to study the rules and laws underlying
their a ttainments, in order to apply them to as many instances
as possible.

In science, on the other hand, the innumerable cases of
observed correlations lead to the question of the more inti-
mate causes of this phenomenon. Our imagination cannot
be content with the outward features of the facts; we wish
to have some idea of their innermost nature. In this Une of
thought the principal difficulty Hes in the absence of definite-
ness in the objects wt have to deal with. We speak of
correlation and interdependency, but we have no idea as
to what the things are that should be related to or depend-
ent upon each other.

Here the idea suggests itself that in order to be corre-
lated the characters must begin by being independent entities,
which through some later means may come into relation with
others. Perhaps this may not be the real way in which
nature proceeds, but at all events it is the way in which we
should proceed in our analysis. Thus we come to the con-
ception of units which govern and control the visible char-
acters and qualities.

A new scope for investigation is opened by tliis concep-
tion. Each organism appears to us as a microcosm, con-
sisting of thousands of elementar}^ entities, which combine
to give it its form and functions. The study of these units
encroaches upon systematic and comparative sciences, as
well as upon the investigations into the physiology and the
evolution of all li\ing beings. All comparison culminates
in the question as to which units are common to the species
under discussion, and which units are the causes of their
differences. Systematic affinity is reduced to the same
principle. It is founded on the community of a more or

flora
rock.

Fig. 96. A. The pansy and some of its parents. B. Viola lutea grandi-
ra. C. Viola tricolor versicolor. D. Viola tricolor lutescens. Af ter Witt-

3"

312 PLANT-BREEDING

less large number of units, whilst divergence must evidently
be the result of the occurrence of different units. The
larger the number of common units, and the smaller that of
varying constituents, the greater will be the affinity.

Wide as are the prospects of solving the most difficult
problems of systematic science and comparative investiga-
tions, and tempting as it is to indulge in a discussion of the
possibihty of the discovery of their ruling laws on the ground
of the principle of units, we must, of course, now hmit our-
selves to questions more directly concerned with our inquiry.

Among these the chief point is, what is to be considered
as a unit? This question is intimately connected with our
main subject, and sufficient facts are at hand to draw at
least a preliminary sketch. At once it brings us upon the
ground of the internal causes of the phenomena of correlation
and so completes the scheme made by our distinction be-
tween these and the external factors.

Our units may be considered from two different points
of view. We may be content with analyzing the visible
characters and with reducing them to independent groups,
or we may ask for some invisible, although material cause,
which constitutes the real source of each unit. This latter
inquiry, however, is as yet wholly of a hypothetical nature,
and so it may suffice to have suggested it, and to return to
the visible features for our further discussion.

There is no reason for assuming that a unit should be
limited to one organ, to one tissue, or to one cell. Quite on
the contrary, it seems probable that a unit may show its
activity in different organs, sometimes even in almost all parts
of a plant. This conception affords a broad principle for
the explanation of a large group of correlations, the corre-
lated external marks being simply assumed to be the expres-
sions of the same internal character. The faculty of pro-
ducing a red or blue color may be taken as an instance. If

THE ASSOCIATION OF CHARACTERS 313

it is considered as a unit, the tint of the stems and foliage,
and that of the corolla and all other parts must no longer be
considered as so many separate marks, but as the results of a
single intimate character. As soon as this is lost, or reduced
to a state of inactivity by the production of a pale variety,
it becomes a matter of course that the change at once affects
all the colored organs, as we have seen is the case of the thorn-
apple, the belladonna, and numerous other instances. The
same explanation holds good for the correlation of fissures,
as seen in the petals and leaves of celandines and brambles.
It is evidently one and the same internal unit which affects
both organs.

If this principle of units is true, it must have an over-
whelming significance in the study of hybridism. In the
first place, all the modes of expression of one unit must stead-
ily keep together, whenever the entire groups of characters
are thrown into one another in crossing. This rule must
hold good in the more simple cases of crossing varieties of
the same species as well as in the hybrids of more widely
distant parents. In thfe first case the rule prevails that the
hybrid is not intermediate between its parents, but bears
the characters of one of them. Hybrids between blue or
red flowered species and their white varieties, between hairy
and smooth forms, between spiny and unarmed parents, and
many other instances could be presented. They show the
marks of the colored, hairy, or spiny parents and are often
not at all distinguishable from these. Here the unit is repro-
duced without being weakened or rather without its divergent
expressions being separated from one another. The second
generation of the hybrids completely supports this concep-
tion. Some plants remain true to the type of the first gen-
eration, but others return to the alternative grand-parent.
Among red-flowered hybrids whites occur, among a spiny
and hairy progeny some smooth ones are seen. But inter-

Fig. 97. Gordon's currant (Ribes Gordonianum), a hybrid of the flowering
currant and the golden currant.

314

B

Fig. 98. A. The flowering currant of the Pacific Coast {Rihes saiigui-
neum). B. The yellow currant {Rihes aureiim).

315

3i6 PLANT-BREEDING

mediates are still lacking, showing that the unit-character
is either present or absent, but cannot be divided into lesser
constituents.

Such spUttings are even more striking, whenever they
are produced on the different branches and flowers of the
same individual plant. The instance of the willow-leaved
Veronica has been dealt with; its flowers are either of a dark
blue or completely white, the unit which produces the dye
being wholly absent or present, but not in intermediate
degrees. A parallel case is that of the hybrid between the
orange and the lemon, which may show the separation of
its units within the same fruits, some parts having the color
and the juice of the orange and others those of the lemon.

Crosses between species are more difficult to understand.
According to the general rule, all the single marks of the
parents are mixed up in the offspring so as to form quite a
new type. But if we look more closely into special cases, it
is often possible to see that definite units of the parents are
recognizable in the hybrids, and that their development is
often the same, though in other cases checked by the new
combination. A notable instance of this rule is a hybrid
between the red and the golden currant (Ribes sanguineum
and R. aureum), which is commonly cultivated in gardens
under the name of Gordon's currant (R. Gordonianum). It
has the form and hairiness of the leaves of its red parent, but
in the flowers the red and golden colors are combined so as
to give an intermediate tinge. The combination, however,
is not at all perfect and easily shows on petals and calyx, its
two distinct component colors. So it is also in the hybrid
of the ordinary and the yellow foxgloves. I have pollinated
the first with the dust of the second and had a beautiful lot
of hybrids which flowered richly during a series of years.
The foliage and spikes were almost those of the yellow parent,
the flowers being intermediate in size, yellow, but with a red

Fig. 99- A. The cultivated snapdragon. B.-G. Its color varieties.
B. Yellow. C. Delila, tube white and lips red. D-E. Flesh-colored.
F. Brilliant, of a fiery red. G. Album, white with a yellow spot on the
lip. H. The calyx and the style after the removal of the corolla.

317

3i8 PLANT-BREEDING

hue, and bearing inside the corolla numerous spots in highly
variable numbers. Such spots are seen in both the parents,
but most beautifully developed in the red species. Many
other instances could be given. The hybrid of the common
and the small-flowered evening primroses (CEnothera biennis
and (En. muricata) has the flovv^ers of one and the spikes of
the other parent. In the culitivated violets the size and yel-
low tinge are derived from one of the parents, the Viola
lutea grandiflora, and so on.

As a rule some characters of one or the other parent may
be more or less easily recognized in the hybrid, but others
are so intricately mingled that our knowledge is wholly insuf-
ficient to single them out. Each of them may be impeded
in its development by the others, and as long as we do not
understand the laws by which such mutual hindrances are
governed, it is impossible to give more than a superficial
analysis.

Crosses may give us an insight into the nature of unit-
characters in still another way. Many so-called characters
are in reality composite entities and it is by means of crossing
that they can be divided into their constituent units. As
an instance I select the color of the flowers and especially
that of the cultivated snap-dragon (x^ntirrhinum majus).
Its large and bright corollas strike our eyes by their fiery
red, and on a closer inspection show a yellow spot on the
under lip, and a paler tinge on the tube. These deviations
from the general color may be considered as indications of
its composite nature. Besides this species a white variety
is largely cultivated. It is not absolutely white, but lacks
the red dye and the yellow tinge of the main parts. The
yellow spot on the under lip, however, has not disappeared,
but is still visible, and almost as well developed as in the
red species. Here we have the first proof of the build-
ing up of the original type out of more simple constit-

■f '*

Fig. loo. Danebrog opium poppy; petals
red with a large white spot at the base.

319

320 PLANT-BREEDING

uents, since the yellow spot is evidently due to a separate
unit.

If, now, we cross the red and the white types, we get,
according to the ordinary rules, hybrids that bear the
marks of the species and not those of the variety. But in
the second generation a spUtting occurs, and it is this spht-
ting which frees the units from one another. A complete
analysis has not as yet been made, but some constituents
have been separated and have proven to be real units. Of
course, only some of the hybrids have but one unit in a pure
condition, others having groups of two or three or even more
of them in all imaginable combinations. But the more
simple forms are easily recognizable among the throng. In
the first place they give proof of the independence of the red
and yellow colors. A pure yellow form exists, lacking all
of the red. It has two units of color, the one being the spot
on the under lip, already mentioned, and the other the general
tinge. The red dye is also produced by at least two units,
one of them being a fleshy color, equally distributed in all
parts of the corolla, except the yellow spot, and the other
being of a bright color, but limited to the Hps. It is a type
called Dehla, and distinguished by its colorless tube. As
is easily seen, the combination of these two units gives the
dark lips and the pale tube of the original species, and this
not only theoretically but also experimentally whenever the
two constituents are combined by crossing.

In the same way the colors and color- designs of other
flowers may be analyzed and their component units sepa-
rated. The most obvious means for almost all cases is the
crossing of the species which has all the units, with the white
variety in which they are absent or at least latent. Such
crosses usually result in the desired sphtting. A most beau-
tiful instance may now be mentioned. It is the separating
of the dark central spot of the opium- poppies from the red

THE ASSOCIATION OF CHARACTERS 321

of the upper part of the petals. It produces the variety
known as the Danish flag and characterized by its broad
central white cross on the red field of the petals.

It goes without saying that these sphttings may not
only be produced by artificial crosses, but must occur also
whenever accidental crosses are brought about by insects
visiting the variety and the species when cultivated side by
side. If this takes place in a nursery, the horticulturist will
recognize the new types, isolate them as such, and put them
on the market. They will prove constant, or at least become
so after some additional splittings. In other words, many
intricately colored species must afford, besides their white
variety a larger or smaller number of types, in which the
constituents of their color-designs are more or less com-
pletely isolated. By this means we can study the units by
simply cultivating and comparing all the commercial varie-
ties of such a species.

Having thus mentioned the different methods by which
unit-characters may become isolated, in order to give proof
of their real existence, we now come to the other side of the
question. Our conception of units was originally based on
the desire of having some principle wliich might explain
the internal causes of correlation, or at least some of them.
We have seen that botanical marks observed in the scales
of an ear of wheat or barley may be indications of hardiness
in winter, of fitness for definite commercial purposes, of
resistance to diseases, and other valuable quahties. In order
to explain such coincidences, we have assumed that unit-
characters are not productive of single marks, but may ex-
hibit their influence in different parts of the plant body.
The same unit may become visible in the color of the stem,
foHage, flower, and fruit, and so it must also be with other
units, which, when added to a type, not only change its
flowers or its leaves, but also affect other organs, physiologi-

322 PLANT-BREEDING

cal qualities, and perhaps even the whole mode of growth
and development.

But if we wish to give a direct proof of this assertion,
comparative study is no longer sufficiently rcHable. Its
units are in reahty hypothetical. Their existence may seem
to be quite obvious and to be in no need of further proof, but
as soon as they are to become the basis for far-reaching con-
clusions they ought to be beyond all reasonable doubt.

Our question is, when one unit is added to or subtracted
from a well-known type, what are the changes which are
thereby produced ? Now such an addition or subtraction is
exactly what we call a mutation, and thus it becomes evident
that only directly observed mutations can give a rchable
answer. Moreover, mutations are so rare that the chance
of two of them occurring together seems too small, or, in
other words, that we may confidently assume that each single
mutation aifects only a single unit.

Considering the mutations of the evening primroses from
this point of view, our conception of the correlative nature
of the different changes which each of them produces will
at once become clearer in its meaning and win the rank of
full experimental proof. Some of them arc more easily de-
scribed and understood than others, but the same general
rules prevail in nearly every single case.

Let us begin with the short-styled variety or (Enothera
brevistylis. Its mutative origin has, as a fact, not been direct-
ly observed, but may be deduced from its occurrence on only
one native locahty and amidst an overwhelming throng of
normal primroses. The unity of its character, has, on the
other hand, been proven by its behavior in crosses with the
parent species. The characteristic mark of this variety lies
in the short style which, instead of pushing the stigmas
above the anthers, hardly reaches the throat of the tube.
Other marks are correlated with this. In the first place,

P

? 3

323

324 PLANT-BREEDING

some characters of the flower are affected, and in the second
place, some of the leaves. In the flowers, the stigma is broad-
ened and flattened and less regularly divided into its four parts.
The ovary, which is inferior in the normal species, is here
only partially so, and its ca-vities are seen to protrude above
the insertion of the calyx tube, occupying thereby the basal
part of the style. How these changes may be brought about
by the same cause that shortens the style, we do not under-
stand. But far less can we guess the connection between
the marks of the flowers and the foliage. The leaves of the
brevistylis have more rounded tips and the plants may, by
this means, be recognized weeks before the development of
the flower buds, and sometimes even in the rosette stage.
This instance of correlation seems analogous to the facts
observed among cereals and other cultivated plants. We
can only acknowledge the fact from the regularity of the
ocC'Urrence of the combination, without even being able
to guess its cause.

Of course, there art also correlations which we may
understand or at least believe we understand. In our case,
one of these is seen in the broader flower-buds of the (E. brev-
istylis, when compared with the CE. Lamarckiana. In the
latter the calyx is extended by the growth of the style, which
presses the stigma from within against its tip. The calyx
being thereby elongated, it is only natural that its form be-
comes more conical as soon as the long style is absent. Per-
haps another mark may be explained in a similar way. At
the time of the ripening of the seeds the (E. brevistylis is
easily recognized by its very small pods, containing hardly
any seed. It may be assumed, although a direct proof is
wanting, that the elongation and narrowing of the ovarial
cavities within the base of the style is an impediment to the
growth of the pollen-tubes, and thus hinders a normal fertil-
ization.

fc5»»Mf*»^'*wr?»—~

Ki^ife ^^.M^r

Fig. I02. A. The short-styled Evening-primrose. B-F. Its parent form.
b. A flower after the removal of part of its petals and stamens, c. The
same without petals, d. The same without the tube and the calyx, e. A
flowerbud. /. Ripe fruits. B-F. The corresponding parts of the parent
species, g. Styles, h. Longitudinal section of ovary, i. Transversal
section of base of style and calyx-tube.

325

326 PLANT-BREEDING

Exactly similar conclusions may be derived from a dis-
cussion of the Oenothera lata, which has often been seen to
be produced from the parent species by a single leap. There
is even less connection between the various marks by which
it is distinguished from Lamarck's primrose. It strikes us
through all the periods of its life as quite another type. The
very first leaves of the young seedhngs differ, being broader
and more rounded at the tip. This type of leaves is pre-
served during the whole life history, and the rosettes, the
young stems, and the branches are distinguished by this
same mark. There can be no doubt that the form of the
leaves during the whole Hfetime is regulated by one single
unit-character. This unit probably causes still another
mark, the extremely sinuous surface of the leaves. Sinuos-
ities, although not lacking in the parent species, are much
more numerous in this mutant form. The weakness of the
stems and the consequent bending of their tips is more diffi-
cult to explain as an effect of the same cause, but it is as
constant a mark as the leaves. More curious is the behavior
of the flowers. These have only one sex, producing no
pollen at all. The anthers are developed and of the normal
size, but in their cavities the pollen is sometimes entirely
wanting, and sometimes sterile, their place being occupied
by the outgrowth of the cells of the inner layer of the wall.
These cells commonly collapse and are absorbed, and so it
is in Lamarck's primrose and in all its other derivatives, but
in the lata they thrive and increase their size until the time
of the shriveling of the anthers.

The correlation between the broad and sinuous leaves
and this inabihty to produce pollen is a phenomenon which
it is at present far beyond our power to explain. But it is
absolutely constant. The lata has been produced anew by
the main strain in my garden more than three hundred times.
A large number of these plants have flowered, and the flowers

Fig. 103. A biennial specimen of tiie Evening
Primrose of Lamarck.

327

328 PLANT-BREEDING

have always borne the same marks, especially the same
deficiency of the pollen. This can be predicted with abso-
lute security from the single inspection of the first leaves
of the young secdhngs.

Here we have the full dupUcate of so many cases of ob-
served correlations, with which we have previously dealt.
But in this case the repeated observation of the origin by a
single leap may be considered as a direct experimental proof
of what, in other cases, can be derived only from comparative
studies. In such a case no chance coincidence, no depen-
dency on similar outer conditions of Hfe, and no other hypoth-
esis can adequately explain the facts. Only the assumption
that one unit-character may affect different organs of the plant
in different and apparently independent ways gives a suffi-
cient idea of their internal connection.

The same correlations may be seen in most of my other
mutants. The scintillans and the oblonga are small types,
recognizable in their youth by their narrow leaves. The
albida is whitish and very dehcate and has its peculiar shape
of spikes and flowers. The laevifolia combines smooth
leaves with a propensity for reducing the petals on the weaker
branches to an ovate form. But the most interesting instance
and the one which almost exactly corresponds to the corre-
lation between botanical and practically valuable characters
of the agricultural crops is that of the (Enothera gigas. Its
botanical marks are the dense foliage, the large flowers, the
swollen flower-buds, and the small, but thick pods with their
less numerous, but bigger seeds. Its cultural feature is its
great tendency to be biennial. The parent species and
most of its other derivatives can easily be cultivated as an-
nuals, and the rubrinervis evidently prefers this condition.
On the other hand, the gigas prefers to develop its stems only
in the second year. Under the conditions existing in my
experimental garden, it ordinarily defies all endeavors to

Fig. 104. A. Spike with almost ripe fruits of Oenothera gigas, a mutant
species. B. The same of Oenothera Lamarckiana, its parent form,

329

33°

PLANT-BREEDING

make it flower and produce seeds in its first year. Ordina-
rily at least one half of the plants remain in the rosette stage,
the remainder producing their stems only late in summer
or towards the fall, and thus having hardly time enough to
display their flowers, and none at all to ripen their fruits.

Fig. 105. A. A rosette of rootleaves of Lamarck's Evening Primrose
in September. B. A similar rosette of one of its mutants {Oen. scintillans)
in the same age.

Only in some very favorable years have I succeeded in saving
seed from annual gigas plants.

Here we have an instance of correlation such as that
between hairiness or form of scales and hardiness in winter
or resistance to diseases. But here the mutative origin of
the type affords a direct proof of the validity of our assump-
tion that such divergent quahties may be the effects of the
same internal unit-characters.

Fig. io6. The smooth-leaved variety of the Evening Primrose {Oeno-
thera laevijolia). a. A side-flower with ovate instead of obcordate petals,
one of the new, highly variable characters of the new form.

331

332 PLANT-BREEDING

By this means the direct observation of mutations sup-
ports the conchisions derived from purely comparative in-
vestigations. Together they teach us the great law of correl-
ative variabihty, by wliich one and the same internal cause
may affect different organs and quahties in widely divergent
ways. This law intimately connects the scientific results
and methods of selection now in use at the Swedish experi-
ment station at Svalof with the principles and achievements
of Burbank in horticultural practice and with numerous
other more or less isolated scientific facts and methods of
practice. It points out the lines for further investigation.
The study of correlations must be carried on on the broadest
possible basis. Minute and apparently small marks must
be analyzed and compared with valuable properties. Every-
where connections will be discovered. Some of them may
be accidental coincidences, and of no further significance,
but others will hold good through large numbers of instances.
From the broadest possible knowledge of these, new princi-
ples of selection wih be derived, and slowly, but surely, we
shall approach a definite knowledge of the meaning of much
that is as yet hidden from our eyes. Then we shall see that
there is no mystery connected with the indications wliich
seedhngs give concerning the fruits they will bear in later
years.

VI

THE GEOGRAPHICAL DISTRIBUTION OF

PLANTS

Among all sciences, that of the geographical distribution
of animals and plants is necessarily, perhaps, the most inter-
national. In crossing the continent of America in order
to reach the much beloved far West, my eye was struck by
the diversified conditions under which vegetation and agri-
culture must thrive. Arid deserts and lofty mountains
contrast with humid and fertile plains, with large forests
and great rivers, with marshes and lakes. Each of these
can, of course, be compared with some parts of Europe, and
though the impression we get is that of essential difference,
the separate parts are as a fact only a repetition of what is
seen with us.

The cause of the diversity is, therefore, not to be sought
in the cHmatic conditions, but rather in the special character
of the vegetation. In x\merican agriculture corn has taken
the place which in Europe is given to the smaller cereals.
So it is also in nature. Everywhere the European traveler
sees new types and new kinds. As a rule they catch his eye
by some common features which are strange to him. Among
these, I mention only the rich colors of the flowers in sum-
mer and of the fohage of trees and shrubs in the fall.

We are thus impressed with one of the great principles
of the geographical cUstribution of living organisms. We
are convinced that the fundamental difference between the
organic beings of the two great continents is not, in the main,
due to their chmates and soils, but that it can have no other
cause than their separate origin from the organisms that
peopled them in previous geological times. One of the best
proofs of the truth of this principle is given by some of the

333

334 PLANT-BREEDING

most common plants of the fields and waste places in Cali-
fornia. Immigrants from Europe are of common occurrence,
and some plants have spread with a most astonishing rapid-
ity. The Napa-tliistle (Centaurea MeHtensis) and the wild
chamomile (Matricaria Chamomilla) are the most obvious
instances, but many other introduced species could be ad-
duced.

It is evident that such new plants are finding conditions
here which suit them as well and perhaps better than those
under which they live in Europe. The same phenomena
are afforded by other species which have been introduced
from America into Europe, and are now common weeds or
even dreaded pests with us. The Canadian water pest, or
Elodea canadensis and the American Azolla (A. carolinen-
sis) are now perhaps the most widely dispersed obnoxious
plants of our canals and ditches, occurring in the largest
numbers of individuals.

Such observations are apt to awaken doubts as to the
real value of the current ideas concerning the nature of the
adaptations of the organisms to their environment. The
Napa-thistle and the wild chamomile are evidently as well-
fitted for the Californian soil and chmate as any of its own
native plants. Notwithstanding this, they have acquired
the quahties which enable them to multiply in such stupen-
dous numbers here, in another country. Whether in their
native localities the soil and the climate were the same, we
do not know, but we may confidently assume that their
living environment was different, inasmuch as it must have
consisted of European plants and animals. And it is gener-
ally conceded that living nature has a larger influence on the
evolution of new species than the purely physical and chem-
ical conditions.

Our doubt is tliis: Are the native plants of Cahfornia
still living under the same influences under which they

GEOGRAPHICAL DISTRIBUTION OF PLANTS 335

originated? If this were so, wc might assume that their
fitness for their present Hfe- conditions has been acquired by
means of adaptation. If not, there is no reason at all for
explaining their characters on the basis of this principle, and
all speculations of this kind are reduced to mere hypotheses,
lacking even the possibiHty of comparative or experimental
evidence.

The current conception tacitly assumes that all or nearly
all living beings originated on the very spots where they are
now found, or, at least, under quite similar conditions. It
is evident that only on this assumption the causal connec-
tion between environment and characters can help us in ex-
plaining the latter. The present life-conditions are called
upon to explain the observed instances of fitness in plants.

If, however, plants have as a rule migrated from their
native spots, then they are now found in environments which
have no right whatever to be considered as the cause of their
characters. Quite on the contrary, the migration and the
dispersion must have been guided by the nature of the species.
Or, in other words: Each plant must have sought out the
conditions where it could thrive best on account of its given
peculiarities.

Thus we come to the conclusion that the relation between
organisms and their present environment is quite the reverse
of what it is commonly assumed to be. The properties of
the animals and plants must be considered as given facts,
and on the basis of these their present distribution is to be
explained. It is readily granted that this proposition only
withdraws the main point from our study, but on the other
hand it brings the investigation along a path of direct
inquiry and experience instead of imiperfectly founded
speculations.

From this point of view the geographical distribution
of plants and animals must be discussed under two different

336 PLANT-BREEDING

headings. One case embraces the widely-spread species,
the other those with a Hmited area. For the first it is instantly
clear that at best only one of their numerous habitats can be
the spot where they have originally been produced. To all
their other locahties they must have been introduced, and, if
we do not consider collective forms but pure and elementary
types, tliis must have happened without changing their
original characters. Now, the question arises, which
locaHty is their native one? Observation teaches that
in almost all instances there is no evidence of a difference
between this one and the others. Therefore, it is simply
impossible to answer this question in any case with sufficient
certainty. It is generally assumed that in the center of the
whole dominion of a plant its native station is concealed,
but this is only a hypothesis, resting on no observational
basis. Quite as well some species might have spread in one
direction only, and then their native spot would lie at the
very end of their realm. Granting that we cannot recognize
this original center of cHspersion, we may turn to a discussion
of the large majority of the observed localities. Some plants
are evidently better fitted for certain stations, while others
prefer different life-conditions. The large group of the
evening primroses may afford instances. In Cahfomia
only one large-flowered species is met with in the wild
state. It is the CEnothera Hookeri which occurs on waste
places along roads and railroads, and may even be seen here
and there in the parks. It is evidently suited to the climate of
CaHfornia, but its dispersion in Arizona and other neighbor-
ing states makes it very probable that it is no real native
Cahfornian, but has only been introduced. In tliis case no
single one of its quahties can possibly be explained by the
demands of its present environments.

Other species of evening primroses give further proofs.
Two of them were introduced into Europe more than a

Fig. 107. Oenothera muricata, a seaside plant, which originated far from

the sea.
337

338 PLANT-BREEDING

century ago, and have spread widely over various countries.
Both have become quite common with us, but prefer dif-
ferent Hfe-conditions. Now it is very interesting to note
that one of them, the smah- flowered form or Oenothera
muricata, prefers the proximity of the sea-shore, whilst
the common species or (E. biennis prefers inland fields and
places. On the sand-dunes along the coast of Holland, this
difference in stations is very striking, the small flowering
type being almost limited to a region of a few miles along the
coast.

How can this noticeable difference be explained ? Espe-
cially, how did the muricata acquire its love for the sea-air
and the sea- winds? All our knowledge of the dispersion
of the evening primroses points to some part of the middle
states of the United States of America as their original
habitat, and so it seems evident that even the muricata was
originally an inland plant, springing up far from any influence
of the sea.

From this special instance we may conclude that at least
in many cases, the geographical distribution of wide-spread
plants is governed by qualities acquired quite independently
of their present life-conditions. Innate propensities govern
their dispersion, and have determined where they should be
crowded out and where they could multiply themselves.
In order to make this conclusion still more convincing, I
might draw your attention to the chronological side of the
question. We are trying to explain the constitution of
forms on the ground of the conditions under which they
are now living. But in doing so, we forget how very old
they are, and how much nature may have changed since
their first origin. Many of our most common species are
known to be older than the glacial periods, their fossil
remains being found in the upper tertiary deposits (e. g.
Statiotes aloides). If they have endured these dreadful

Fig. loS. Wulfenia carinthiaca, which grows almost only on
the Giirtnerkugel in Carinthia.

339

340 PLANT-BREEDING

times of cold and of subsequent repeated migration, how
can we know under what circumstances they originated?
Observation teaches which of the Hfe-conditions available at
the present time are the best suited for them, but there is
no reason to assume that they have been produced under
similar ones. Plants originally inland forms may now
prefer the sea-shore, because they are crowded out else-
where, and many an alpine plant would without doubt
prefer a lower and warmer region were it not for dread of
the enemies it has to meet there.

Opposed to the common plants, which have evidently
migrated far from their place of birth, are the so-called
local species, which inhabit only one mountain, or one valley,
or are Hmited even to the slope of a single hill. Here,
at first sight, two possibihties occur. The species may be
of recent origin, and may not as yet have found time for
spreading itself outside of its native spot. Or it may be
old, perhaps slowly dying out. In this case it may once have
been distributed over large areas, but have disappeared
from almost all points. Only there where it enjoyed
sufficient isolation or sufficiently suitable hfe-conditions
has it survived. The study of these conditions may then
show us the minimum of requirements for continuing its
existence, but it does not tell in any way how these precious
quahties may have originated. Who does not remember the
description of the bright dark-blue Wulfenia, as given by
Ouida in her "Moths" (II 271), when Correze brought
this rare plant from the almost inaccessible heights of the
Gartnerkugel in Carinthia? There it grew upon the slopes
of the mountain, and nowhere else in all the world was it
found. Evidently it is only a rehc of times that have passed
away.

How can we determine whether in any given case a
local species is nearer its origin than its decline? In most

Fig. 109. The smooth-leaved campion, a
local plant of Bohemia, with a useless character.

341

342 PLANT-BREEDING

cases, the question is difficult to decide, but there is one
instance in which most authors agree in acknowledging
the youth of the type. This is the case of the local types
of those polymorphic species, whose numerous elementary
forms inhabit different stations, but are collected together
in the same region. Here the relations between Ufe-con-
ditions and characters may be studied, and the question
may be answered on what quaUties the occurrence on the
observed spots depends. Two instances may be given,
since they are illustrative of the real nature of the question.
One is a smooth variety of the ordinary campion, which is
found almost only in a grove near Miinchengratz in South-
ern Bohemia (Lychnis Preslii). Here it grows abundantly.
But there is no imaginable connection between this mountain-
slope or its forest and the lack of hairs on the leaves of the
local campion. No other explanation seems possible than
that of an accidental mutation, which changed a character
in a harmless way and thus left the chances of survival for
the new variety simply the same as they were for the species
itself. The other case is that of two alpine species of milfoil.
They are nearly similar in botanical marks, even to such a
degree that their differences may easily be overlooked.
They are different, however, in their demands on the chem-
ical constituents of the soil, the one preferring calcareous
and the other silicious formations. The Achillea moschata
prefers the Hmy and the A. atrata the siliciferous slopes.
In Switzerland w^herever both species occur in the same
valley they are strictly Umited to their particular kind of
soil, the one form wholly excluding the other. But as soon
as only one species occurs in a valley, it is indifferent to the
nature of the soil and grows on lime as well as on silica.
Now, how can we tell whether they have originated separately,
each on the soil which is now best for it, or whether they
had a common origin and have only spread afterward, each

Fig. no. Two Alpine species of milfoil. A. The Achillea atrata
of calcareous soils. B. The A. moschata of siliciferous soils.

343

344 PLANT-BREEDING

multiplying itself most rapidly where the conditions proved
to be most suitable ?

So it is in many cases. The present life-conditions
allow the occurrence of a species whenever they have
no relation at all to its special characters, or whenever
these characters are fitted for them. If not, a plant
may be accidentally introduced and perhaps thrive for
some years, but in the long run it will always be extermi-
nated.

The same principle may be appHed to the origin of a new
form. If its new character is harmless or more or less
suited, the type will thrive as well as the parent form from
which it derived its origin. If, however, it proves to be
injurious, it goes without saying that the form will be con-
demned to extermination after a longer or shorter struggle
for existence. Its only chance of escaping this judgment
Ues in migration, by which, perhaps, it may find elsewhere
more suitable life-conditions.

Returning to our general discussion we may state that
the study of the relations of Hving organisms to their present
environment must be revised and rebuilt upon quite new
principles. The qualities of the plants are not the problem
to be solved. The question is how the given quahties
of the species are suited to the environment, and how they
enable the organism to hold out against its present enemies,
and against the dangers of cUmate and winter. The question
has often been discussed whether we are right in speaking
of the use of some character or in saying that a quahty
serves a distinct purpose. No doubt, much abuse has been
made of these terms, and the common assumption that all
quahties must serve some special purpose is evidently
exaggerated. The only point which is open for inquiry is
the question on which marks of an organism depends its
possibihty of hving and multiplying itself on the spot where

GEOGRAPHICAL DISTRIBUTION OF PLANTS 345

we see it, and which other characters are indifferent in the
actual struggle for life.

In other words, the principle of adaptation, as one of the
main parts of the theory of evolution, should be separated
from the study of the geographical distribution. Tliis
latter science itself should be divided into two parts, one
of which would be concerned with the deUmitation of the
regions inhabited by organisms of various degrees of affinity,
while the second would have to explain the directly observed
facts of local occurrence and actual migration. The first
of these two parts is a comparative science and is directly
related to the theory of the common origin of living beings.
The second must become an experimental inquiry into the
relationship between the quaUties of the plants and those
of the environment, which it may prefer or endure. All
speculations upon the relationship of organisms to special
features of this environment which attempt to explain
larger groups of characters on the assumption of some
adaptation, are, to my mind, as yet merely poetical descrip-
tions of the way in which we should like to understand
and admire nature, but not facts capable of direct proof.

Desert plants afford an instance which may give a
clear appreciation of the two contrasting methods of explain-
ing the nature of plants. According to the current view
they are most astonishingly speciaHzed and adapted for
large regions where it is impossible for other plants to
thrive. Although belonging to numerous natural famihes,
and therefore showing hardly any genetic affinity among
themselves, they enjoy a group of common features which
show the closest imaginable relation to their arid environ-
ment. Three main types of desert plants may be distinguished.
The most common is composed of the low shrubs with green
stems and twigs, a loose mode of branching, and small
coriaceous leaves or, in some instances, with no foliage at

^

-..-. ,-^

"^--.

1

y

V

^i

'^

>

^ *

±

r ""^i

v^ ^J^^

r

! '

1 A "'*~- )| |7

■ "jiLJai

U^

! \ "^a^^jJ

MrmV> f

Wi

>v ^^r ^

r~"'\jY^

s ^ ^

s

V

f^

Fig. III. Palo Verde, or Parkinsonia microphylla, typical desert plant

from Tucson, Arizona.

346

Fig. 112. Palo Christi, or Koeberlinia speciosa, a typical desert plant from

Tucson, Arizona.

347

348 PLANT-BREEDING

all. All their visible marks point to a reduction in the
use of water, the evaporating surface being as thoroughly
reduced as possible. Under the ground, the development
of their root-system is quite the reverse. The roots are
long and widely branching, penetrating to a considerable
depth, thus enabhng the plants to procure the necessary
water.

The two other types of desert plants are the cacti and the
annual weeds. The roots of the cacti are spread laterally,
instead of growing to any considerable depth. They may
be said to drain the surface all around the plants. They ab-
sorb the rainwater at the periods of those short but heavy
showers, which for a short time moisten the soil and stimu-
late vegetation. This water is brought into their fleshy stems
and stored up, that it may be used afterward during the
long rainless seasons. During rainy weathei* the stems
of the cacti are seen to swell, shrinking again in the succeed-
ing periods of drought. The annual weeds of the desert

r

are distinguished by the shortness of their hfe-timc, this
being hmited to the few weeks of rainy weather in the
spring. As soon as the summer begins and the soil
is drying, their hfe-cycle is completed, and only the dead
stems and the numerous seeds remind the visitor of the
profusion of flowers which have vanished.

In the mind of a botanist strolling on the arid soils
amidst these most strange and astonishing forms of vegeta-
tion, the question necessarily arises: Are all these species
natives of the desert, and have they acquired their special
characters under the influence of the long periods of dryness
and the insufficiency of standing water in the soil? Is it
the desert which has made them such as they are now,
apparently admirably suited for these extreme Kf e-conditions ?
Or, on the other hand, are they perhaps only a selected
few from among the widely differentiated forms, which

349

350 PLANT-BREEDING

are everywhere abundant in richer regions and on more
favorable soils? Arc the plants of the deserts only such
as can endure the hardships of these unfavorable surround-
ings, all others being stamped out, as soon as they try to
transgress the Hmits of these peculiar areas? Is not the
popular saying that they are cast out, to live on the desert,
nearer the truth than the current scientific conception,
wliich regards them as the product of their present environ-
ment?

To my mind the answer to these questions is given by
the plants themselves. Tliis answer is: They all prefer
more favorable conditions to those which are given them.
They endure the desert, but only with dithculty. Their hfe
is nearer starvation than enjoyment. They are multiply-
ing themselves in a prodigious manner, not, however, from
luxuriance, but on account of the absence of competition.
They do not thrive, nor do they unfold their full stature
and qualities as they might under better conditions. They
greatly prefer irrigated grounds or the moist air of the
forest, and only here display their real nature. Even
cacti are originally forest plants, and may be seen stoutly
growing between densely thronging shrubs. Thus the
conviction is forced upon us, that desert-plants are not,
as a rule, the product of aridity. They may have originated
anywhere else, under any other conditions. But through
their pecuhar quahty of enduring drought, they attained
their rapid multiphcation as soon as in their migration
they reached the arid regions and there found themselves
free from competition.

So it seems to me in all those beautiful cases of fitness
for peculiar or extreme influences. We do not know how
they have been acquired. We may imagine that usefulness
in the struggle for Hfe has preserved some quahties, the
bearers of injurious characters being easily stamped out. We

351

352 PLANT-BREEDING

may sketch the development of the spurs of the orchids in
connection with the lengtli of the proboscis of bees and
butterflies, but we cannot directly observe the changes which,
■ we assume, are brought about by such influences. In all those
cases it is equally possible, and in some even probable, that
they have not been originated in the way in which the
plants are now using them. The higher the degree of
differentiation, the more probable our mode of explanation
may be, but in the more simple and ordinary cases, includ-
ing the desert plants and many similar instances, the environ-
ment has only selected the suitable forms from among the
throng, and has no relation whatever to their origin.

Present distribution is the effect of migration, and
migration is governed and directed by the given characters
of the species. It produces the intimate relationship of the
organisms to their environment, to climate and soil as well
as to all their vegetable and animal competitors. But in
this the qualities of the organisms are the causes, and the
distribution is the effect.

1

INDEX.

"Abundance" plum, 211.

Achillea atrata, 342, 343 fig.; mos-
chata, 342, 343 fig.

Adaptation, 345.

Advertisement of pedigree wheat,
40 fig.

Agricultural breeding. Discover}'
of Xilsson and, 93.

Agricultural experiment station at
Svalof, 48 ff., 272; of Kansas,
125 fig.; of Minnesota, 103, fig.

Agricultural plants. Discovery of
elementary species of, 29.

Agrostis, 1 70.

Alhambra plum, 213.

Amaryllis, 162; hybrids, 207.

Amelioration, German methods of
selection and, 56; Gradual, 31;
of agricultural plants by selec-
tion. Explanation of, 99; of ap-
ples and pears, 256.

Amsterdam, Experiment garden at,

15 %-, 143 fig-. 323 fig-
Analysis of varieties of cereals, 68.
Anthocyanin, 246, 248.
Anthoxanthum, 170.
Apples, Amelioration of, 256;

Seedless, 188, 257.
Ajiricot and plum hybrids, 2:8.
Asclepias, 170.
Atropa Belladonna, 243 fig.
Australian star - flower, 169 fig.,

172; Improved everlasting, 171

fig.
A.vena elatior, 285 fig. ; Flower of,

278 fig.; Forms of, 286.
Azolla carolinensis, 334.

Barley, breeding for stiff culms,
63; Constancy of, 89; Hallett's
Chevalier, 39 fig., 44, 269; Meal-
iness of, 287; Prentice, 65; Pri-
mus, 240, 269; Princess, 65:
selection for strong straw, 239;
Spikelet and flowers of, 279 fig. ;
Transparency of, 287.

Barrenness in corn, 141, 145 fig.

Bartlett plum, 226.

Bateson on discontinuous evolu-
tion, 8.

Beach plum, 212.

Beans, \\'indsor, 248.

Beech, Seedling-plants of, 295 fig.

Beets, Amount of sugar in, 304;
Methodical study of, 284; Se-
lection in sugar-, 94; Sugar-,

307-

Belladonna, 243, 244.

''Bellevue de Talavera" wheat, 32
fig-, 33-

Berries and flowers, 244.

Blackberry, \\'hite, 189.

Bore-wheat, Svalof, 267 fig.

Brambles, 185; Laciniate, 249 fig.

Breeding, Agricultural, 93 ; blocks
of corn, 155 fig.; by isolation of
individuals, 67; corn, 107 fif.;
corn for oil, 108 fig. ; Correla-
tions in agricultural, 255 flf. ;
English vs. German method, 65 ;
German method of, 46; Meth-
ods of corn, 133; of cereals, 29
ff^. ; of corn, History of, 130;
plots, 137.

Erodiaea, 170.

354

PLANT-BREEDING

I>ud sports, 232.

Bulbs of hyacinths, 247.

Burbank (Luther), De \'ries and
Shull, 165 fig.; Experimental
garden of, 163 fig. ; Farm of, at
Santa Rosa, Cal., 161 fig.; Por-
trait of, 1 58 fig. ; Production of
horticultural novelties by, 159
ff. ; Methods of, 159.

Burbank cauna, 200; giant prune,
179 fig.; plum, 170, 211; Shasta
daisies, 195 fig. ; sugar prune,
181 fig.

Butt summer wheat, 75 fig.

Cactus, Giant, 349 fig. ; hybrid, 193
fig.; Spineless, 168, 192; Spine-
less edible, 193 fig., 226, 227 fig.,
228, 229 fig.

Calla sethiopica, 204; albo-macu-
lata, 207; Elliottiana, 206; "Fra-
grance," 204; Fragrant, 224
hastata, 206; Nelsoni, 206, 232
Pentlandi, 206; Rehmannii, 232
Tiny, compared with normal
size, 205 fig.

Campion, Smooth-leaved, 341 fig.

Cannas, Burbank, flaccida, flower-
ing, and Tarrytown, 200.

Capsules and general development,
Correlation of, 307.

Carnegie grant, 162.

Celandine, 251 fig.

Centaurea Melitensis, 334.

Cephalipterum Drummondii, 172.

Cereals, Breeding of, 29 ff; Corn
differs from other, 120; Ele-
mentary species among, I OS ; Or-
igin of variability of, 84; Sports
of, at Svalof, 85; Svalof breed-
ing of, 48.

Cereus giganteus, 349 fig.

Chamomile, Wild, 334.

Chance seedlings, 222.

Characters and environment, 33 s;
in nature. Association of, 237;
Parallelism of apparently inde-
pendent, 296; Unit-, 16, 242,

309-

Chelidonium majus, 251 fig.

Cherry, Mahaleb, 223 ; and plum
hybrids, 218.

Chestnut, Spineless, 234.

Chevalier barley, 39 fig., 44, 269

Chrysanthemum segetum, 11, 13
fig-, 235.

Classificators, 287.

Clematis hybrid, 209.

Close pollination of corn, 122.

Clovers, Correlations in, 258;
Hastening of germination of,
262; Pitchers of, 293 fig.;
Types of, 282.

Collections of selected plants, 28S.

Color, and form, Correlations be-
tween, 250; and taste. Correla-
tions between, 248; of hybrids
of Veronica longifolia, 247; of
thorn-apples, 246; -varieties and
seeds, 244.

Columbine, Flowers of, 241 fig.;
hybrid, 209.

Concordea pea, Svalof, 69 fig.

Constancy of elementary species,
100 ; of minor variations, 118;
of species, 8.

Cope on discontinuous evolution, 8.

Corn, Barrenness in, 141, 145 fig. ;
breeding, 107 ff. ; Breeding
blocks of, 155 fig.; breeding.
History of, 130; breeding. Meth-
ods of, 133; Comparative trial
of progeny of, 137; Cross-polli-
nation of sweet, 123 fig.; Dent.
114; Detasseling of, 140; differ."
from other cereals, 120; Equal-
ity of kernels in, 147; Flint,
114; for oil. Breeding, 108 fig.;
hybridizing, 125 fig. ; Individual
rows of, 13s fig.; Inflorescence
of, 121 fig.; Kernel of, 153 fig.;
Methods of testing, 137; mon-
strosities, 1 13 fig., 1 15 fig., 117;
Pistillate flowers of, iigfig. ;
Pod, 114; Pollen of, 122; Polli-
nation of, 122; Pollination of,
by hand, 126, 129 fig.; Pop, 114;
Ramified cob of, 115 fig.; Selec-
tion in, 134, 148; Soft, 116;
Staminate spikelet of, 119 fig.;

INDEX

355

Sweet, II 6, 149 fig.; Types of,
III fig., 114; yield per acre, no.

Correlation, 18, 244, 258; between
color and form, 250; between
color and taste, 248; Factors of,
304; in agricultural breeding,
255 ff.; in fluctuating variabil-
ity, 289 ff.; in panicles of oats,
265; Methodical study of, 271
ff. ; of capsules and general de-
velopment, 307 ; within the flow-
ers, 250.

Corylus Avellana laciniata, 7 fig.

Cross-pollination of corn, 122; of
sweet corn, 123 fig.

Crosses, 316; Accidental, 80; not
always successful, 219.

Crossing, New characters not pro-
duced by, 187; New varieties
by, 174-

Culture, Pedigree, 42; Pedigree,
of Lamarck's evening primrose,
20.

Currant, California, 184; Color in
flowering, 247; Gordon's, 314
fig., 316; Hybrid of, 316; Flow-
ering, 315 fig.; Yellow, 315 fig-
Dahlia, Fragrant, 224.

Daisies, P>urbank's Shasta, 195 fig. ;
Shasta, 196, 198 fig.

Danebrog opium poppy, 319 fig.

Darwin, Natural Selection discov-
ered by, 91; on origin of spe-
cies by sports, 6; theory of des-
cent, I, 90.

Datura Stramonium, Color of, 246.

Datura Tatula, Color of, 246.

Descent, Darwin theory of, i, 90;
Lamarck theory of, i, 90.

Desert botanical laboratory at Tuc-
son, Arizona, 351 fig.; plants,

345-
Detasseling of corn, 140.
De Vries, Burbank and Shull, 165

fig-
Dewberry, Californian, 186, 187.
Dipsacus sylvestris. Twisted stems

of, 144 fig-
Distribution, and migration, 352;
Geographical, of iilants, 333 ff.

DoUo on discontinuous evolution.

8.
Dracocephalum moldavicum, 11.
Drechsler, breeder of cereals, 46.

EI?eagnus, 185.

Klodea canadensis, 334.

Elofson, Work of, 277.

luivironment and characters, 335.

I'pigeia repens, 225.

Epilobium hirsutum. Elementary
forms in, 100.

Equisetum Telmateja, Twisted
stems of, 1 44 fig.

Eryobothrya japonica, 183.

Eschscholtzia californica, 234.

Everlasting, 172.

Evolution, and mutation, i ff. ; Dis-
continuous, 8; Nilsson on slow,
14; Theory of, i; Time re-
quired for slow, 4.

I-'asciations, 144, 293.
Fertilization of corn, 122, 151; of

evening primroses, 252.
Figwort, Seedling-plants of, 295

fig-
Flag-oats, Svalof, 76 fig.
Flax, Correlations in, 258.
Flowers, Berries and, 244; of

corn, 119 fig.; Varieties of fruits

and, 178.
Fluctuation, 5.

l-'ouquieria splendens, 351 fig.
Frit-fly, 264.
Fruits and flowers, Varieties of,

178.
Fruwirth, Work of, 294.
Funk Brothers Seed Company,

breeders of corn, 132.

Garden, Experiment, at Amster-
dam, IS fig-; 143 fig-; 323 fig-;

of Luther Burbank, 163 fig.
Geographical distribution of plants

333 ff-
Germination and size of seeds,

261; of clover. Hastening of,

262.
Golden Drop Wheat, 44.
Grading selected plants, 288.

356

PLANT-BREEDING

Grape, Pierce's, 232.

Grasses, 170; Methodical study

of meadow-, 284.
Gregory, J. J. H., and Son, 162.
Grenadier wheat, Svalof, 266 fig.
Grop pea, Svalof, 283 fig.
Gwallig, Work of, 294.

Hallett, E. F., breeder of cereals,

38.

Hallett's advertisement of pedi-
gree wheat, 40 fig.; Chevalier
barley, 39 fig. ; "Original Red
Wheat," 41; wheat, 39 fig.

Hand pollination of corn, 126, 129

fig.

Hays, W. M., breeder of wheat,
45; Work of, 10 1.

Hazelnut, Oak-leaved, 7 fig.

Heine, breeder of cereals, 46.

Heuchera, Hybrid, 197, 201 fig.;
micrantha and sanguinea, 199

History of corn breeding, 130.

Holden, P. G., breeder of corn,
132.

Hopetown oats, 35; wheat, 35.

Hopkins, Cyril G., breeding corn
from single ears, 131; Discov-
eries of, 154.

Hops, Correlations in, 258.

Hordeum erectum, 269.

Horsetail, Twisted stems of, 144

fig.

Horticultural novelties by Luther
Burbank, Production of, 1 59 ff.

Horticulture, Mutations in, 221 fif.

Hunnemannia fumariaefolia, 170.

Hunter's wheat, 41.

Hyacinths, Bulbs of, 247.

Hybrid amaryllis, 207; apricot, 218:
cactus, 193 fig. ; cactus seedlings,
191 fig.; cherry, 218; clematis,
columbine, California poppy,209;
Heuchera, 197, 201 fig. ; currant,
314 fig.; plums, 210, 218; pop-
pies, 232, 233 fig.; poppies.
Leaves of, 231 fig.; Tobacco and
petunia, 219; \'eronica longifo-
Ija, 247; walnut, 173 fig., 174,
17s fig., 177 fig.

Hybrids, 72, 313; Splitting of, 80;
L^nit-characters in, 16.

Hybridization, a means of increas-
ing variability, 186; and selec-
tion, 202.

Hybridizing corn, 125 fig.

Inflorescence of corn, 121 fig.
Isolation of individuals, Breeding
by, 67.

Kansas agricultural experiment
station, 125 fig.

Kelsey plum, 213.

Kernel of corn, 153 fig.

Kceberlinia speciosa, 347 fig.

Korshinsky on discontinuous evo-
lution, 8.

Laboratory at Tucson, Arizona,
Desert botanical, 351 fig.

Lamarck theory of descent, i, 90.

Lathyrus heterophyllus, pratensis,
and sylvestris, 284.

Learning, J. L., breeder of corn,
130.

Leaves, Pitcher-like, 292.

Le Couteur, breeder of cereals, 33.

Leguminous plants. Elementary
types of, 284.

Leland Stanford Junior Univer-
sity, 162.

Lilacs, Double-ilowered, 188.

Lilium pardalinum, 208.

Lime tree. Pitchers of, 293 fig.

Linaria vulgaris peloria, 11, 12 fig.

Lochow, Petkus von, breeder of
rye, 45.

Lolium, 170.

Loquat, 183.

Lotus uliginosus, 284.

Lundberg, Work of, 277.

Lupinus angustifolius. Seeds of,
244.

Lupins, Seeds of, 244.

Lychnis Preslii, 341, 342.

Magnolia, Pitchers of, 293 fig.
Marguerites, European, 199.
Marigold, Double, 235; Double
corn-, II, 13 fig., 303 fig.

INDEX

357

Matricaria chamomilla, 334.

Matthiola incana, Selection of
double, 238.

Maynard plum, 211.

Meadow-grasses, Methodical study
of, 284.

Methods of breeding, English vs.
German, 65; German, 46; of
Burbank, 159; of corn-breeding,
133; of producing improved ra-
ces, Svalof, 67 ; of selection and
amelioration, German, 56; of
selection developed by Nilsson,
Summary of, 90; of testing and
comparing, 61; of testing corn,

137.

Migration, 335, 345; and distribu-
tion, 352.

Minnesota, Agricultural experi-
ment station of, 103 fig.

Mokry, breeder of cereals, 46.

Monstrosities, 142, 144, 292; of
corn, 113 fig., 115 fig., 117-

Mungoswell's vi'heat, 35.

Mutability, 6, 100.

Mutation, 6; and evolution, i ff. ;
at Svalof, 85; in horticulture,
221 ff.; of evening primroses,
322.

Nicotiana, 170; afifinis, 209; glauca,
209.

Nightshade, Deadly, 243 fig.

Nilsson, Hjalmar, and agricultural
breeding. Discovery of, 93 ; Dis-
covery of elementary species of
agricultural plants by, 29; por-
trait, 28; method of selection,
Summary of, 90; methods, 104;
on slow evolution, 14; Work of

2T7-
Nilsson-Ehle, Work of, 2-j-].

Oat - grass, Spikelet of, 278 fig. ;
Wild, 285 fig.

Oats, Correlation in panicles of,
26s; Hopetown, 35; Panicles of,
263 fig. ; Races of, 36; Shirreff,
35; sports at Svalof, 89; Stiff-
branched Svalof, 82 fig. ; Svalof
flag-, 76 figure; with bending

branches, Svalof, 86 fig.; with
spreading branches, Svalof, 83
fig.; with stiff branches. Panicle
of, 275 fig. ; with weak branches.
Panicle of, 273 fig. ; with weak
branches, Svalof, 87 fig.

a-'nothera albicaulis, 170; biennis.
253, 250, 338; biennis. Elemen-
tary forms in, 100; biennis X
muricata, 318; brevistylis, 325
figure; brevistylis. Elementary
forms in, 100; brevistylis, Mu-
tative origin of, 322; gigas, 22.
23 fig-, 328, 329 fig. ; Hookeri,
336; Lamarckiana, 17 ff., 324,
329 fig.; laevifolia, 331 fig.; lae-
vi folia. Elementary forms in,
100; lata, 20, 326; leptocarpa,
22; muricata, 337 fig., 338; na-
nella, 21 fig., 22; oblonga, 24,
328; rubrinervis, 21 fig., 125 fig.,
328; scintillans, 19 fig., 328;
scintillans. Rosette of, 330 fig.

Oil, Breeding corn for, 108 fig.;
Selection for, 154.

Opuntia Engelmanni, 328; vulga-
ris, 228.

Oscinis frit, 264.

Palo Christi, 347 fig. ; \^erde, 346.

Pansy, 311 fig.

Papaver orientale, 209; pilosum,
233 fig. ; Rhoeas, 209, 234; som-
niferum, 209; somniferum, Pis-
tillodous, 297.

Parallelism of apparently inde-
pendent characters, 296.

Parkinsonia microphylla, 346 fig.

Pea, Svalof Concordia, 69 fig. ;
Svalof Grop, 283 fig. ; Svalof
Solo, 281 fig.

Peas, Kinds of, 280; sports at
Svalof, 89; Tedin's work on,

255-
Pearl summer wheat, Svalof, 74

fig.
Pears, Amelioration of, 256.
Pedigree, cultures, 42; cultures of

Lamarck's evening primrose, 30;

of spineless cactus, 168.
Peloria, 293.

358

PLANT-BREEDING

Petkus, Rye of, 46.

Petunia, Hybrid between tobacco

and, 219.
Pierce's grape, 232.
Pisum arvense and sativum, 255.
Pitchers, 292.
Plots, Breeding, 137.
Plum, 21S fig.: and apricot hy-
brids, 218; and cherry hybrids,
218; Bartlett, 226; Burbank,
170: Hybrid, 210; Satsuma, 170;
Sorts of, 211 ff.; Wickson, 175.
Plumcots, 218.
Pollen of corn, 122.
Pollination, 220; of corn, 122; of
corn by hand, 126, 129 fig. ; of
evening primroses, 252 f. ; of
sweet corn. Cross-, 123 fig.
Poppy, Blue, 234; Californian,
209; Common, 209; Danebrog
opium, 319 fig.; Hybrid, 232,
233 fig.; Leaves of hybrid, 231
fig.; Opium, 209; Pistillodous
opium-, 297; Polycephalous opi-
um, 299 fig. ; Scarlet California,
234; Seedling-plants of, 295 fig.;
Seeds of opium, 244; Young
opium, 301 fig.
Potatoes, Correlations in, 258;

Methodical study of, 284.
Prentice barley, 65.
Primrose, Evening, 170, 250; Flow-
ers of Evening-, 252 fig. ; Fruits
of Evening-, 305 fig. ; Hybrid of,
318; Lamarck's evening-, 17 ff.,
327 fig. ;Mutations of evening-,
322; Rosette of Lamarck's even-
ing-. 330 fig-; Seedling-plants of
Evening-, 295 fig.; Short-styled
evening-, 325 fig; Smooth-leaved
variety of the evening-, 331 fig.
Primus-barley, 240, 269; berry,

186.
Princess barley, 65.
Pringle's wheat, 36.
Progeny, Mixed, 72 ; of corn. Com-
parative trial of, 137; Uniform,
72.
Protein, Selection for, 154.
Prune, Burbank giant, 179 fig.;
Burbank sugar, 181 fig.; Cali-

fornia sugar, 172; Stoneless,
189, 190 fig., 226.
Piunus Americana X nigra, 213;
Mahaleb, 223; maritima, 212;
Pissardi, 213, 215 fig.; Simoni,
213, 226; triflora, 176, 213.

Ouetelet's law of variability, 5.
Quince, Japanese, 183; Selection
of, 239.

Races, Pure, 77: Self-dependent,
95 ; Types of, 94.

Raspberry, Cuthbert, 187; Sibe-
rian, 186.

Records, Value of scientific, 71.

Rhodanthe, 170.

Rhubarb, Crimson, 172.

Ribes, aureum, 315 fig.; Gordon-
ianum, 314 fig., 316; sanguin-
eum, 184, 247, 315 fig., 316;
sanguineum glutinosum, 185;
sanguineum X aureum, 316.

Richardia africana, 204.

Riley, James, breeder of corn, 131.

Rimpau, breeder of cereals, 46.

Rimpau's rye of Schlanstedt, 95,
97 fig.

Rubus Californicus, 186; fruti-
cosus laciniatus, 249 fig.; Sibi-
ricus, 186.

Rye of Petkus, 46; of Schlan-
stedt, 46, 95, 97 fig.

Satsuma plum, 170, 211.

Schindler, Work of, 294.

Schizanthus, 170.

Schlanstedt, Rimpau's rye of, 95,
97 fig. ; Rye of, 46.

Schribaux on Schlanstedt rye, 96.

Scott on constancy of species, 8.

Scrophularia nodosa. Seedling
plants of, 295 fig.

Seed-grain society for Sweden, 54.

Seedlings, 295 fig. ; Chance, 222;
Hybrid cactus, 191 fig.; Seeds
and color-varieties, 244; Size
and germination of, 261; Size
and integuments of, 259.

Selection, and amelioration, Ger-
man method of, 56; Causes of
improvement in repeated, 66;

INDEX

359

developed by Nilsson, Summary
of method, 90; discovered by
Darwin, Natural, 91; Explana-
tion of amelioration of agri-
cultural plants by, 99; for oil
and protein, 154; for strong
straw, Barley, 239; is intra-spe-
cific, 94; of corn, 134; of double
common stock, 238; of quinces,
239; of samples, 70; Hybridiza-
tion and, 202; of individuals,
71; in sugar-beets, 94; Natural,
and mutation, 9; Principle of
continuous, 90 ff. ; Principle of
natural, 2; Repeated, 150, 222;
Sufficiency of initial, 73.

Selections, Burbank's, on large
scale, 167.

Shasta daisies, 196, 198 fig.; Bur-
bank's, 195 fig.

Shirreff, Patrick, breeder of cer-
eals, 34.

Shirreff's bearded red wheat, 36;
bearded white wheat, 36; oats,

35-
Shull, Burbank and De Vries, 165

fig.
Silene odontipetala, Seedling

plants of, 295 fig.
Slow evolution, Nilsson on, 14;

Time required for, 4.
Snapdragon and its color varie-
ties, 317 fig-
Society for Sweden, Seed-grain,

54-

Solo pea, Svalof, 281 fig.

Species among cereals, Elemen-
tary, 105; Constancy of elemen-
tary, 100; Elementary, of agri-
cultural plants, 29; Origin of,
92; Origin of elementary, 81;
Origin of, by mutations, 9, 26;
Scott on constancy of, 8.

Splittings in hybrids, 316.

Sports, 223; at Svalof, 89; at
Svalof, Cereal, 85.

Spurs, Cause of, 241.

Star-flower, Australian, 169 fig.,
172; Improved everlasting Aus-
tralian, 171 fig.

Statiotes aloides, 338.

Stipa, 170.

Stock, Common, 238.

Stocks, Seeds of, 244.

Svalof, Agricultural experiment
station at, 48 ff., 272; breeding
of cereals, 48 ; Bore-wheat, 267
fig. ; Concordia pea, 69 fig. ; flag-
oats, 76 fig. ; Grenadier wheat,
266 fig. ; Crop pea, 283 fig. ;
method of producing improved
races, 67 ; oats. Stiff-branched,
82 figure; oats with bending
branches, 86 figure; oats with
spreading branches, 83 fig. ; oats
with weak branches, 87 figure;
Pearl summer wheat, 74 fig.;
Solo pea, 281 fig. ; village, 50.

Sweden, Seed-grain society for, 54.

"Sweet Brotan" plum, 211.

Syringa azurea plena, 188.

Tannin, 248.

Tarrytown canna, 200.

Taste, Correlations between color
and, 248.

Teasels, Torsions among, 142;
Twisted stems of, 144 fig.

Tedin's work on peas, 255.

Testing corn. Methods of, 137.

Thistle, Napa-, 334.

Thorn-apples, Color of, 246.

Toadflax, Peloric, 11, 12 fig.

Tobacco, and petunia. Hybrid be-
tween, 219; Fragrant, 170, 209;
Pitcher-like leaf of, 291 fig.

Torsions among teasels, 142.

Tiifolium incarnatum, 261.

Triticum polonicum, 30 fig.

Unit-characters, 16, 242, 309.
Units, 310.

\'ariability, 3; Constancy of mi-
nor, 118; Correlations in fluctu-
ating, 289 ff.; Correlative, 332;
Fluctuating, 5, 100, 183; Hy-
bridization a means of increas-
ing, 186; Kinds of, 182; of the
cereals. Origin of, 84; of corn
within the varieties, 118; of ray-
florets, Fluctuating, 306; Pro-

360

PLANT-BREEDING

duction and augmentation of,
182: Range of, 183.

Varieties, Agricultural, 84; by
crossing, 174; comparative stud-
ies, 79; Horticultural, 84; of
cereals. Analysis of, 68; of
fruits and flowers, 178; Testing
new, 78; \'ariability of corn
within the, 118.

X'erbena, Fragrant. 224.

Veronica longifolia, 245 fig., 247.

Vetch, Correlations in, 258; Seeds
of white, 244.

Vetches sports at Svalof, 89;
Types of, 282.

Vicia Cracca, and Faba, 248.

Victoria wheat, 41.

\'iola lutea grandiflora, 311 tig ;
tricolor, 31 1 fig.

W'allden, Work of, 277.
Walnut, Hybrid, 173 fig., 174.
fig., 177 fig.; Sweet, 225-

175

Wheat. Butt summer, 75 figure;
Golden Drop, 44; Hallett's, 39
fig.; Hallett's advertisement of
pedigree, 40 fig. ; Hallett's orig-
inal red, 41; Hopetown, 35;
Hunter's 41; Mungoswell's, 35;
Poland, 30 fig.; Pringle's 36;
Races of, 32 fig.; Shirreflf's
bearded red, 36; Shirreff's
bearded white, 36; sports at
Svalof, 86; Svalof Bore-, 267
fig.; Svalof Grenadier, 266 fig. ;
Svalof Pearl summer, 74 fig. ;
\'ictoria, 41.

Wickson plum, 175.

Wind-pollination of corn, 122, 124.

Witt, Work of, 277.

Wulfenia carinthiaca, 339 fig., 340.

Zea Mays amylacea, 116; inden-
tata, 114; saccharata, ii6, tuni-
cata, 114.

The Open Court Biological Series

HUGO DE VRIES

Species and Varieties, Their Origin by Mutation, Lectures
delivered at the University of California by Hugo
de A>ies, Professor of Botany in the University of
Amsterdam. Second thoroughly revised and cor-
rected edition, with portrait in photogravure. 1906.
Pages xviii, 847. Price $5.00 net. (21s. net.)

It is evident that the new theory of mutations must be recog-
nized in all discussions of questions as to origin and develop-
ment. For instance, if the empirical view of consciousness be
taken, why should it not be quite possible that this has
appeared in the phylogenetic development of certain species
as a mutation ? And what becomes of those arguments for
design which have been based on adaptation by slow accumu-
lative changes? Evidently the work of De Vries may well
prove to be an epoch making contribution to the advance of
knowledge. It makes the study of evolution in part experi-
mental, modifies the current views as to origin, selection and
adaptation, and finds a place for non-heredity and discon-
tinuity, for chance and irregularity. — Edward G. Spaulding
in The Philosophical Review.

EDWARD DRINKER COPE

Among American naturalists Cope takes decidedly a most
prominent rank. His numerous original contributions
to paleontology, and observations in other lines have
been largely accepted by his colleagues, while his in-
terpretation of the doctrine of evolution, has been a
powerful factor in the formation of modern thought.

The Primary Factors of Organic Evolution, by the late E. D.
Cope, Ph. D., ^Member of the United States National
Academy of Sciences : Professor of Zoology and Com-
parative Anatomy in the University of Pennsylvania.
Second edition. 1904. 121 illustrations. Pp. 550.
Tables, bibliography and index. Cloth $2.00 net.
(10s.)

"Will stand as the most concise and complete exposition of
the doctrines of the Neo-Lamarckian school hitherto published.
A most valuable text-book for teachers and students." —
Science, N. Y.

"A work of unusual originality. No one can read the book
without admiring the intimate knowledge of facts and the
great power of generalization which it discloses." — Prof. J.
McK. Cattell.

"K thoughtful and scholarly presentation imencumbered
by guesses at facts or reasoning from probabilities." — Ameri-
can Register, Paris.

2 THE OPEN COURT BIOLOGICAL SERIES.

TH. EIMER

Professor Eimer was the teacher of Professor Weismann
at Tuebingen. He has written vokuninons works and
his system has received much attention in Germany.
His theory is based mainly on the observation of
butterflies, while his famous disciple, Weismann,
relies chiefly on the generalization of facts derived
from the observation of ants. Although they re-
mained personal friends, they differ in their con-
clusions.

The pamphlet On Orfhodenesis (i. e., evolution in a defi-
nitely determined direction) is a condensed statement
of his theory made by the professor's own hand, and
it acquires an additional zest by being a tilt at arms
directed against Weismann's Germinal Selection. (See
page 4.)

On Orthogenesis (Definite Evolution) or the Impotence of
Darwinian Selection in the Formation of Species. By
Th. Eimer, Professor of Zoology in the University of
Tuebingen. Translated by Thomas J. McCormack.
19 cuts. Pp. 56. Paper 25c. (Is. 6d.)

This little brochure was written in reply to Vv^'eismann's
"Germinal Selection." Prof. Eimer is a Neo-Lamarckian,
and his special doctrine of orthogenesis is declared to be a
universally valid law, framed to show that organisms develop
in definite directions, without regard for utility, through purely
physiological causes, through the transmission of acquired
characters, through the combined agency of the constitution of
the animal and the effects of outward influences.

CARL VON NAEGELI

Naegeli was the first to propose the general theory of cell-
formation as accepted today. His little brochure on
"A Mechanico-Physiological Theory of Organic Evo-
lution" is a synopsis of his great work on evolution
and will render his difficult theories accessible to
English-speaking students, to whom they have been
hitherto almost a sealed book.

A Mechanico-Physiological Theory of Organic Evolution.

Summary. By Carl von Xaegeli. Translated by \'. A.
Clark and F. A Waugh, of the University of Vermont.
The only original account of Naegeli's theories in
English. Pp., 52. Price, paper, L5 cents. (9d.j

THE OPEN COURT BIOLOGICAL SERIES. 3

FERDINAND HUEPPE

Professor Hueppe has been the leacUng authority in bac-
teriological lines and he could lind no better inter-
preter to make his book accessible to English readers
than Dr. Edwin O. Jordan, Head Professor of Bacteri-
ology in the L^niversity of Chicago.
The Principles of Bacteriology. By Dr. Ferdinand Hueppe,
Professor of Hygiene in the University of Prague.
Translated from the German and annotated by Edwin
O. Jordan, Ph. D., Professor in the University of
Chicago. 28 cuts. Five colored plates. Pages, 465 — x.
Price, $1.75 net (9s). Invaluable to the physician,
the scientist, the student of hygiene, and practical
people in all walks of life.

"In place of a mere repetition of methods and enumeration
of species, Professor Hueppe has grappled with the fundamental
questions concerned, and has in clear language given a cogent,
philosophical and scientific account of bacteria and their rela-
tions to the processes with which they are said to be associated.
. . . . It is the work of a master of the subject, who is not
only a scientific man in the sense of being an ol^server, but also
in the sense of having a true philosophical mind." — The Lancet.

"To one who wishes to know what bacteriology has accom-
plished and what problems are still undergoing solution, no-
thing can serve better than this outline of Professor Hueppe."
— Science.

"The publishers deserve special credit for the acceptable
form in which this work is presented ; and the clearness of the
type, as well as of illustrations, place this volume beyond all
criticism." — Medical Fortnightly.

GEORGE JOHN ROMANES

Romanes is generally characterized as the man upon whom
the mantle of Darwin has fallen. He was a disciple
and an intimate personal friend of the great expounder
of the doctrine of evolution. His three-volume work,
Darwin and after Darwin, together with the additional
volume. An Examination of Weismannism have become
classical.

Darwin and After Darwin, An Exposition of the Dar-
winian Theory and a Discussion of Post-Darwinian
Questions, by George John Romanes, M. A., LL. D.,
F. R. S., Honorary Fellow of Gonville and Caiits
College, Cambridge. Three volumes. $4.00 net.

Part I. The Darwinian Theory. Third edition. 1901.
Pp. xiv., 460. Cloth $2.00.

Part II. Post - Darwinian Questions: Heredity and Utility.
Second edition. 1897. Pp. xii., 344. Cloth $1.50.

4 THE OPEN COURT BIOLOGICAL SERIES.

George John Romanes — Continued
Part III. Post -Darwinian Questions: Isolation and Physio-
logical Selection. 1897. Pp. 181. Cloth $1.00.
An Examination of Weismannism, by George John Romanes,
Al. A., LL. D., F. R. S., Honorary P'ellow of Gonville
and Cains College, Cambridge. Second edition. 1899.
Pp. ix., 221. Cloth $1.00 net.

D. KERFOOT SHUTE, M. D.

Dr. Shute's First Book in Organic Evolution originated in
the lecture room, its author being the professor of
Anatomy in the medical department of the Columbian
University at Washington. Students of this subject
v;ho have not the benetit of attending a university can
easily post themselves Avith the help of this little
volume, so terse and so clear in all essentials.

A First Book in Organic Evolution, an Introduction to the
Study of the Development Theory, bv D. Kerfoot
Shute, M. D. Pp. xvi., 285 ,- 39 illustrations, 9 in
natural colors. Price cloth, $2.00 net (7s. 6d. net).

"It is difficult to see in what way this volume could be im-
proved. The elementary part of the doctrine of evolution is
thoroughly covered and without a word wasted, and the arrange-
ment of the matter presented is scholarly.. It is just such a
volume as teachers everywhere are looking for to give those
interested a first-class idea of the modern biological beliefs."
— American Inventor.

"It seems to us that the author has attained no small success
in his difficult task, for the book is clean and interesting; it is
neither too simple nor too difficult; it is conspicuously free from
crankiness and dogmatism, and it is evidently the work of one
who has had experience in the task of teaching. Prof. Shute
is to be congratulated on the success with which he iias accom-
plished a difficult and serviceable piece of work." — Xafure.

AUGUST WEISMANN

On Germinal Selection, as a Source of Definite Variation,
by August V\'eismann. Translated from the German
by Thomas J. McCormack. Second edition. 1902.
Pp. 87. Cloth 60c net (3s. net).

"Forms the crown and capsheaf of Weismann's celebrated
Theory of Heredity."

In connection with the subject of this book, see also An Examinalion of
Weismannism, by George John Romanes, page 4, and On Ortho-
genesis ; or, The Impotence of Darwinian Selection in the Formation of
Species, by Th. Eimer, page 2, which was written in reply to
Weismann's Germinal Selection.

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