MASS CULTURE 559 
characters. By selecting, through a number of generations, the 
most desirable individuals for seed, eventually individuals that are 
homozygous and breed true to the desirable character may be 
secured, and a better race of plants thereby established. Muta- 
tions also afford considerable opportunity to improve plants by 
selection. In case individuals appear that are more desirable due 
to a mutation, a more desir- 
able race of individuals is 
immediately secured by 
selecting and propagating 
these mutants. Through 
selection, races of plants much 
more desirable than the ordi- 
nary types from which the 
plants were selected have 
been produced. Grains, for- 
age crops, Strawberries, 
Blackberries, Melons, fruit 
trees, etc., have been im- 
proved by selecting and prop- 
agating those plants having 
more desirable features than \ 
the ordinary types. In this z 
way plants have a ae Fic. 484.— Heads of Timothy, show- 
proved - yield (F ug: 483 and ing improvement by selection. After 
484), ability to resist drought Hays. 
and disease, length of period 
required for maturing (Fig. 485), and many other ways. There 
are two methods used in improving plants by selection, the mass 
culture and pedigree culture. 
Mass Culture. — This is the oldest method of plant breeding. 
This method employs large masses or fields of plants, known as 
mass cultures, from which to select. For example, in applying 
this method to the breeding of small grains, the plant breeder, 
desiring to produce a better yielding race, goes through the field 
and selects those plants with heads having the largest number of 
grains. From the next year’s crop grown from the seed of the 
plants selected the previous year, the best yielding plants are 
again selected for seed, and year after year he continues to select 
until a race more or less constant for high yield is obtained. 
