VARIETIES BY SELECTION 



117 



How Varieties Originate. During the past one hundred years 

 a great many new varieties of wheat have been produced, in fact, 

 most of the varieties now in cultivation have been introduced during 

 the past sixty years. There are two methods by which most of these 

 have been originated. The first is by selecting a single plant of 

 unusual quality and increasing this until a supply of pure seed, all 



II w 





FIG. 47. Types of wheat grains. Top row, hard spring, hard winter, red winter. Bottom 

 row, white winter, Polish wheat, durum. 



from one plant, is obtained. The second method is to artificially 

 cross one or more varieties, thus producing new types, and to select 

 some desirable type from this cross. 



Varieties by Selection. Wheat lends itself to this method of 

 improvement exceptionally well, as it is self-fertilized (p. 25). 

 When a plant is found of superior type, it can be depended upon 

 to produce plants true to type, without variation, for almost an in- 

 definite period. This is in marked contrast to a cross-fertilized plant 

 like corn or rye, which usually must be carefully selected for several 

 years to fix a type. 



