VEGETABLE CYTOLOGY 
77 
Starch grains may be grouped, according to the condition in 
which they are found in the cells of storage regions into three 
kinds, viz.: simple starch grains , compound starch grains and fill 
starch grains. 
Simple starch grains are such as occur singly. Compound starch 
grains occur in groups of two, three, four, five, six or more and are 
designated as two, three, four, five, six, etc., compound, according 
to the number of grains making up the group. Fill starch grains 
are small grains filling up the spaces between the larger grains in 
storage cells. These are common in commercial starches. 
Method of Examining Reserve Starches. —Many of the reserve 
starches are used commercially, such as potato, corn, rice^ maranta, 
oat, wheat, sago, tapioca, etc., and it frequently becomes necesssary 
for the microscopist to determine their purity or their presence in a 
sample of food or drug. The following characteristics should be 
noted in determining the identity or source of the starch. 
1. The shape of the grain. 
2. Whether simple or compound or both; if compound, the number 
or range in numbers of grains composing it. 
3. The size of the grain in microns. 
4. The position of the hilum, if distinct; whether central or excen- 
tric (outside of the center). 
5. The shape of the hilum and the degree to which it is often 
fissured. 
6. The nature of the lamellae, whether distinct or indistinct; if 
distinct whether concentric (surrounding the hilum) or eccentric 
(apparently ending in the margin and not surrounding the hilum), 
or both, as in potato starch. 
7. The color of the grains when stained with dilute iodine solu¬ 
tions; whether indigo, blue, purple, red or yellowish-red, etc. 
8. The appearance under polarized light. 
9. The temperature at which the paste is formed. 
10. The consistency of the paste. 
