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 hnprove 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 

 way plants have been im- 

 proved in yield (Figs. 483 and 

 484), ability to resist drought 

 and disease, length of period 



required for maturing (Fig. 480), 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 j^ear'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. 



Fig. 484. — Heads of Timothy, show- 

 ing improvement by selection. After 

 Hays. 



