62 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



those of rice or oat), with distinct central cleft and varying from 

 0.005 to 0.012 mm. in diameter. 



Potato Starch occurs as a more or less finely granular powder, 

 and appears to have less tendency to form coherent masses than 

 arrowroot starch. The grains (Fig. 20) are somewhat shell-shaped, 

 having distinct lamellae and a circular point of origin of growth, which 

 is at the smaller end of the grain. They vary in size from 0.005 to 

 0.125 mm., there being a large number of smaller, somewhat ellip- 

 soidal or spheroidal grains, and a few 2- or 3-compound grains. 

 Under the micropolariscope the grains show a distinct cross, and a 

 striking play of colors when a selenite plate is used. On heating the 

 starch to a temperature of 65 C. or treating it with very dilute alkali 

 or acid solutions, the grains swell to four times their original size and 

 finally burst. 



Maranta or Arrowroot Starch. There are a number of com- 

 mercial kinds of this starch, depending upon the countries in which 

 it is produced. Bermuda arrowroot is in the form of somewhat hard, 

 irregular granules or masses, varying from 1 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. 20) vary in 

 shape from ellipsoidal to ovoid or oblong, and from 0.010 to 0.065, 

 mm. 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. Montserrat arrowroot closely resembles 

 the Bermuda starch, but the grains are a little larger and more of 

 them show the cleft. St. Vincent arrowroot is slightly darker in 

 color and is in the form of masses or granules, which are sometimes 

 20 mm. in diameter. The starch grains resemble those of the 

 Bermuda arrowroot, but the grains having clefts are more numerous. 



The arrowroot starches all show a distinct cross with the micro- 

 polariscope and a marked play of colors when a selenite plate is used. 

 These starches usually contain about 15 per cent of water, the 

 remainder being mostly starch. 



Other Starches. Among the other commercial starches the fol- 

 lowing may be mentioned: 



a. Consisting of Single Grains; Yam starch (from several species 

 of Dioscorea) occurs in narrow, ellipsoidal grains, 0.030 to 0.050 mm. 

 long, with distinct lamellae and point of origin of growth at narrow 

 end. Canna starch (tous les mois arrowroot), derived from several 

 species of Canna, occurs in broadly ellipsoidal or ovoid grains varying 

 from 0.050 to 0.125 mm. in diameter and with distinct lamellae and 

 circular point of origin of growth. Bean starch consists of ellipsoidal 



