CROP CHEMISTRY 



117 



Com seed is rich in starch and fat. The starch is used 

 as such, or converted into glucose (Section 52). The fat is 

 extracted and forms corn oil (Section 69, b). Sweet corn 

 contains a considerable portion of its carbohydrate in the 

 form of sucrose. Corn is low in ash. 



Oat seed is higher in crude fiber and ash than the other 

 grain seeds due to its very considerable hull. It is corre- 

 spondingly lower in digestible carbohydrates. The proportion 

 of fat is also high, being equalled only by that of corn. 



Rye seed has a relatively low protein content like corn 

 seed, and is low in fat like barlev. 





# 



Fig. 25. — Seed crop: Wheat. Agronomy Department, Pennsylvania 



Station. 



Wheat seed (Fig. 25) has no particularly noticeable con- 

 stituent as far as percentage goes. Its starch is the chief 

 constituent of flour and one of its proteins deserves particular 

 mention in this connection. It is a protein called gliadin, to 

 which wheat flour owes its stickiness or tenacity when mixed 

 with water, and on which the baking qualities depend, serving 

 to keep the baked loaf light. Carbon dioxide formed by the 

 yeast puffs out the sticky mass into man}' minute cells, the 



