76 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 Dayeauana, 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 <l 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. 
