182 



AGRICULTURAL CHEMISTRY 



in outline, and has a slightly concave center. There are 



but few markings or 

 rings (see Fig. 74). 

 The granules vary 

 in size from 0.05 to 

 o.oi millimeter in 

 diameter. Corn- 

 starch is somewhat 

 smaller (0.02 to 0.03 

 millimeter) , more 

 angular than wheat 

 starch, and has a 

 Fig. 74. wheat starch. star-shaped center 



or helium (see Fig. 75). Oat starch is composed of 



a number of small 



segments forming a 



compound grain, or 



mass, each segment 



in itself a complete 



structure. Barley 



and rye starch 



grains are somewhat 



similar to wheat. 



In some vegetables, 



as the parsnip, the 



starch grains are 



minute. Fig. 75. Cornstarch. 



236. Chemical Properties. Starch is composed of car- 

 bon, 44.44 per cent. ; hydrogen, 6.17 per cent. ; and 

 oxygen, 49.39 per cent. Its formula is (C 6 H 10 O 5 ) n . The 



