558 PLANT BREEDING 
more for size than the embryos developed by a much smaller 
plant which has grown in less favorable conditions. To com- 
pare plants as to what is really in their cells, the conditions 
under which the plants were grown must be considered. It is 
for this reason that it is much better to select seed Corn from the 
field than to select it from the crib; for by the first method the 
conditions under which the plants developed 
can be considered and their genetic consti- 
tution better estimated. 
In addition to Johannsen’s investigations 
of inheritance in Beans and a number of 
other plants, there are many other experi- 
ments that tend to establish the fact that 
little is gained by selections in pure lines, 
unless mutations happen to occur. For 
example, as previously cited a long series of 
selections in a pure line of Oats to increase 
the yield secured no results. Likewise selec- 
tions in pure lines of Wheat to intensity and 
fix a desirable variation have given no re- 
sults. In each generation plants having the 
desirable variation were selected for seed, 
J but selections carried on this way for a 
Fic. 483.—Heads number of generations did not increase the 
of Wheat, showing average of the variation. 
pecan % a In vegetative propagation, where the pro- 
vearaclection im 2°8Y does not develop from seed but grows 
which the plants from vegetative structures taken from the 
bearing the largest parent, some variations, such as bud sports, 
heads were selected that are often not inheritable through seed 
a olay Haare can be perpetuated. Such is true in such 
Vitios: plants as Strawberries, which are propagated 
by runners, and in fruit trees, which are 
propagated by grafting. But modifications that are simply 
responses to some peculiarity in the environment are not per- 
petuated even by vegetative propagation. 
Although selection often fails to produce the desired results, 
nevertheless, selection is one of the chief means of improving 
plants. A mass of plants, such as a field of grain, is a mixture 
of individuals most of which are heterozygous for one or more 
