76 VEGETABLE DRUGS WITH ORGANIC STRUCTURE. 



hilum, whether a point, a Hne, or a star-shaped figure, 

 etc. ; finally, the presence or absence of markings, the so- 

 called concentric annulations which are brought out most 

 sharply by the polariscope. 



In the higher plants two main types are to be distin- 

 guished: Assimilated Starch and Reserve Starch. The 

 latter is partly starch of assimilation which has been dis- 

 solved and has passed through the leaves and into the 

 bark, where, passing from cell to cell, it is called transi- 

 tory starch and is often in small grains 2 to 5 microns 

 in diameter. From here it passes on and is found stored 

 up in roots, stems, tubers, and seeds to serve as a reserve 

 food-product. It is in this process of making the reserve 

 starch that the activity of many of the leucoplastids is 

 apparent, though reserve starch may perhaps be made 

 without them. This reserve starch is generally in larger 

 sized grains, which may measure from 30 to 200 fx in di- 

 ameter.* 



Starch grains vary widely in shape and size, being 

 roundish, elliptical, or ovate. Their edges may be 

 rounded. They may be angular, simple, made of in- 

 dividual grains or sometimes crowded together as a 

 compound grain with many-sided granules. • At times 

 their structure appears perfectly homogeneous, again 

 they are distinctly laminated. In many grains there is 

 a point, the hilum, which is in the centre, centric, or to one 

 side, eccentric, around which these lamellae are arranged 

 in concentric rings. Sometimes the hila are more than 

 one, in which case a compound grain is formed. (Fig. 8.) 



Both the physical and chemical structure of the starch 

 grain is imperfectly understood. It was at one time 

 held that the starch grain was made up of two different 

 bodies, starch cellulose (also called amylodextrin) and 

 granulose, the former staining yellow with iodine, the 

 latter blue. A later view has been that starch cellulose 



* A. Meyer: Die Starkekomer, 1895. 



