786 



BOTANY AND PHARMACOGNOSY. 



I to 6 mm. in diameter. When rubbed between the fingers it is 

 reduced to a smooth powder, which is velvety to the touch. The 

 starch grains (Fig. 316, B) vary in shape from ellipsoidal to ovoid 



D 











OoO 



(9 o o ^ ^ n 





Fig. 316. A, potato starch grains showing the excentral and circular point of origin 

 of growth, and lamellEe; B, maranta starch grains showing fissured point'of origin of growth, 

 and distinct lamellae; C, wheat starch grains showing indistinct point of origin of growth, 

 and lamellee; D, com starch grains, which are more or less polygonal in outline and have a 

 3- to s-angled point of origin of growth. 



or oblong, and from lo to 65 ^u, in diameter. The lamellae are 

 mostly indistinct and there is usually a transverse or crescent- 

 shaped cleft at the middle or near the broad end of the grain. 



