176 BOTANY OF CROP PLANTS 



Of course, there is a marked variation in the proportions 

 of these parts, and in their chemical composition. 



Chemical analysis of the above parts shows that the hull 

 contains less protein (about 4 per cent.) than any other part 

 of the grain. The endosperm is richest in protein, containing 

 20 to 25 per cent. The horny endosperm contains about 

 90 per cent, starch and 10 per cent, protein. The starchy 

 endosperm is poor in total amount of protein (5 to 8 per 



Fig. 65. — Variation in the shape of corn grains. Which is the best propor- 

 tioned kernel? Why? (After Mich. Agr. Exp. Sla. Bull. 34.) 



cent.). The germ is rich in oil, being composed of about 35 

 to 40 per cent, of oil and 19 to 20 per cent, protein. As 

 much as 80 to 85 per cent, of the total oil content of the kernel 

 occurs in the embryo. 



In high-protein corn kernels, the horny endosperm ex- 

 tends up to and comes into contact with the embryo, 

 the tip starch being entirely separated by it from the crown 

 starch. In low-protein corn kernels, the amount of horny 

 endosperm is reduced, tip and crown starch being continuous 

 between it and the embryo. The embryo is much larger in 

 high-oil kernels than in low-oil kernels. 



