246 



CHAPTER VII. 



STARCH IN THE LECUMINOS/E. 



Starch is found in all plants, and some form reserves, 

 either in their roots, as, for instance, the Yam bean {Dolichos 

 bulbosus), or in their seeds, like the cereals. 



The seeds of the Leguminos^e, though less rich than 

 those of cereals, nevertheless contain from 30 to 50 per cent, 

 of starch. There are exceptions : several contain high pro- 

 portions of fat, and others, as will be seen later, contain 

 only a very small amount ; however, their proximate com- 

 positions differ very slightly. 



Starch is a ternary substance belonging to the group of 

 carbohydrates. Its formula corresponds to that of cellulose 

 and dextrine, with a variant in the coefficient representing 

 the molecule (CgHjoOs). 



Starch is formed by special corpuscles or plastids. 

 These plastids occur in the protoplasm and are divided into 

 special colourless leucoplasts or amyloplasts, and chloro- 

 plasts which constitute the chlorophyllose bodies. In the 

 case of the embryos the general protoplasm itself seems occa- 

 sionally to secrete starch. 



M. Dubard, in his course on " Colonial Applied Botany," 

 explains the formation of starch grains as follows : — 



" When the grains appear towards the centre of the 

 parent leucoplast they remain for a verv considerable period 

 surrounded by its substance, and growth takes place in an 

 almost uniform manner over the whole of their surface, the 

 result being a grain with a central nucleus. If, on the other 

 hand, the birth of the grain occurs towards the peripherv it 



