SOMATIC SEGREGATION 
Variations in Plants May Be Divided in Two Classes, One of Which Breeds True 
While the Other Does Not—Modern Work Shows Importance of Former 
Class in Practical Breeding—Further Study May Aid in Under- 
standing Causes of Variation in General. 
E. J. Kraus 
State Agricultural Experiment Station, Corvallis, Oregon 
ORTICULTURAL literature 
fet generally, and particularly that 
which deals with ornamentals, 
abounds in references to bud 
variations, bud sports or node sports 
according to the notion of any particular 
writer. Anyone dealing with plants 
in quantity is impressed by the dif- 
ferences exhibited by individuals, dif- 
ferences which often it would be 
desirable to perpetuate, if possible. It 
has been argued that, if vegetative 
propagation means simply the dividing 
up of an individual into many inde- 
pendent parts, all of which are still the 
same individual, then the extent to 
which a plant which possessed particular 
merit could be multiplied and dissemin- 
ated, would be limited only by the 
relative ease of propagation. As a 
result, considerable work has _ been 
attempted along the lines of selection 
of better strains of many kinds and 
varieties of plants. Practically the 
whole idea of pedigreed nursery stock, 
the selection of runners in strawberries, 
and the reworking to another strain of 
unprofitable trees or orchards for greater 
yields or better fruit, is based on the 
question of bud variation and bud 
selection. While the evidence from 
most of the experiments so far con- 
ducted along these latter lines is 
negative, it is by no means safe to 
conclude that there is nothing in the 
idea of improvement by such methods. 
The greatest difficulty which has arisen 
and led to confusion has been the 
failure to recognize the difference be- 
tween those unstable variations due to 
purely local conditions and those which, 
while they may be due to local con- 
ditions to some extent at least, are a 
real part of the plant organization and 
persist even under widely changed 
environment. 
Bud or somatic variations are sub- 
ject to a broad classification, much as 
are seminal or seed variations. Three 
classes are recognizable: modifications 
(fluctuations), segregations, and muta- 
tions. The first class is observed by 
far the most commonly, and _ has 
furnished the material for the larger 
part of the experiments which have been 
conducted with an attempt to deter- 
mine whether superior strains could be 
built up and maintained entirely by 
the selection of vegetative parts. The 
second class occurs in individuals of 
hybrid, or supposed hybrid origin (the 
term being used in its broad sense), or 
in those individuals in which some 
apparently new character has arisen, 
but remains associated with the original 
form and at times exhibits itself wholly 
independently to a greater or less 
extent. To illustrate: an example of 
this latter sort is the manifestation of 
pure white in the green and white 
variegation of many plants, or the pro- 
duction of self-colored flowers by cer- 
tain individuals which normally bear 
striped flowers. To the third class 
belong sudden wide changes or depart- 
ures from the normal character of a 
plant, such as double flowers, purple 
foliage, certain instances of the white 
areas in foliage, fastigiate forms and 
the like, which apparently are new to 
that individual. it is difficult, clearly 
to differentiate the second and third 
classes, and if one believes that muta- 
tions are merely a result of hybrid 
1Read before the twelfth annual meeting of the American Genetic Association, at Berkeley, 
Cal., August 5, 1915. 
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