192 



THE CEREALS IN AMERICA 



variations in content of fat ranging from two and a half to 

 seven per cent. 



260. Breeding for Protein. — The relative proportion of glossy 

 and white endosperm varies largely in the grains of different 

 ears of the same variety of maize. In an average ear of Burr's 

 white (dent variety) ten and two^tenths per cent of protein was 

 found in the glossy endosperm and seven and eight-tenths per 

 cent in the white endosperm. (226) Hopkins finds forty-two 

 per cent of all the protein of the grain in the endosperm, and, 

 also, holds that the aleurone layer, which also has a high per 

 cent of protein, is larger in maize selected for high protein 

 content. As the ratio of glossy to white endosperm is readily 

 estimated by making selections of a few grains from each ear, 

 assuming the above propositions estab- 

 lished, maize may be bred for high or 

 for low protein content. By this method, 

 maize has been bred which contains 

 but six and seven-tenths per cent of 

 protein and as high as fourteen and 

 four-tenths per cent. 



Since the embryos contain a higher per cent of 

 protein than the glossy endosperm and about the 

 same percentage as the aleurone layer, it has been 

 suggested that the variations in the per cent of pro- 

 tein were largely due to variations in the size of the 

 embryos. Hopkins, however, has gone into a rather- 

 elaborate investigation to show that variations 

 in the percentage of protein are due primarily to 

 variations in the glossy endosperm and the aleurone 

 layer and only secondarily to the variations in the 

 embryo. 1 



261. Breeding for Starch. — In order 

 to breed for high starch content, we 

 have only to breed for low protein and low oil content, as, 

 practically speaking, the percentage of carbohydrates (principally 



The grains on the left contain 

 the higher percentage of pro- 

 tein indicated by the higher 

 proportion of glossy or corne- 

 ous endosperm as compared 

 with the white or soft endo- 

 sperm, and, also, possibly, by 

 the larger embryo. (After 

 Hopkins.) 



I IlL Bui, 87, pp. 96-101. 



