7 6 



PHARMACEUTICAL BOTANY 



the underground parts, such as rhizomes, tubers, corms, bulbs 

 or roots, where the leucoplasts store it in the form of larger-sized 

 grains called Reserve Starch. This type of starch is generally 

 characteristic for the plant in which it is found. It constitutes 

 stored-up food for the plant during that period of the year when the 

 vegetative processes are more or less dormant. 



Structure and Composition of Starch. Starch grains vary in 

 shape from spheroidal to oval to chonchoidal to polygonal. They 



FIG. 35. Cell of Pellionia Daveauana, showing starch-grains. The black, 

 crescent-shaped body on the end of each grain is the leucoplast. Greatly enlarged. 

 (Gager.) 



are composed of layers of soluble carbohydrate material and prob- 

 ably other substances called " lamella," separated from each other by 

 a colloidal substance resembling a mucilage in its behavior toward 

 aniline dyes. They contain a more or less distinct highly refractile 

 point of origin or growth called the " hilum" which also takes the 

 stain of an aniline dye. The layers of carbohydrate material stain 

 variously, blue, indigo, purple, etc., with different strengths of 

 iodine solutions. Each grain is covered with a stainable elastic 

 membrane. 



