PRODUCING NEW VARIETIES 171 



It will be observed that wheat and all the mill by-products 

 are richer in protein than corn, while corn is richer in carbo- 

 hydrates than any of the wheat products. 



METHODS OF IMPROVEMENT 



215. Wheat Will Not Mix. Wheat, being close-fertilized 

 is one of the comparatively easy crops to improve, because 

 selected plants do not become mixed with undesirable ones, 

 as is the case with corn. It is probable that occasionally 

 some cross-fertilization occurs, but it is so seldom as to be 

 unimportant. If several varieties of wheat are grown in 

 one plat, any one plant will produce pure seed regardless of 

 the plants surrounding it. This fact enables one to use 

 large numbers of individual plants in improvement work. 



216. Breeding by Selection. The most common method 

 of improving wheat is by selection. A large number of 

 wheat plants grown under perfectly uniform conditions will 

 vary greatly in yield and in other respects. Advantage 

 should be taken of this fact in breeding by eliminating all 

 of the poorer plants, and reproducing only those capable of 

 giving the best returns. A very common method is to grow 

 on uniform land from one thousand to several thousand 

 plants of the variety of wheat to be improved. At harvest 

 time, twenty-five or fifty of the highest-yielding plants are 

 saved, and the seed from each plant kept in a separate 

 package. With the seed from each of these selected plants, 

 separate plats are planted to test the ability of the selected 

 plants to continue to give large yields. This comparative 

 test is continued for at least three years; the plant giving the 

 highest average yield for three years in the small plat is 

 increased as rapidly as possible, to furnish seed for the 

 main crop. 



