VEGETABLE CYTOLOGY 



77 



Starch grains may be grouped, according to the condition in 

 which they are foiihd 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. 



