202 POWDERED VEGETABLE DRUGS 



power of the compound microscope the starch granules stand out most 

 clearly, revealing many highly diagnostic differences in structure. 

 These structural differences are as follows. 



1. Arrangement and Grouping. Starch granules may be simple 

 or compound, or they may occur in aggregates. The corm of Colchi- 

 cum contains typical compound starch granules. The starch granules 

 of the potato, of the arrowroots, of wheat and of rye, are largely simple. 

 Rice and oats contain aggregates, also found in aconite and in other 

 plants. 



2. Form. They may be polygonal (corn), round or discoid (wheat, 

 rye, barley), pear-shaped (potato), kidney-shaped (bean), bell-shaped 

 (sweet potato), spherical (blood root, pepper, allspice), very irregular 

 (sago), osyter shell form (some of the arrowroots), etc. The ends may 

 be truncately cut (orris root, ginger, curcuma). 



3. Position of the Hilum. This may be centric or excentric. The 

 excentricity may vary from slight (as in Phytolacca and Belladonna) 

 to nearly 1-12, and higher, (as in Curcuma and in ginger). 



4. Form of the Hilum. In many starches the hilum is indistinct 

 (as in wheat and barley), in others it is very prominent (bean, colchi- 

 cum, orris root). It may be radiately fissured or star-shaped, X- 

 shaped, linear, V-shaped, Y-shaped, or U-shaped. The excentric 

 hili are as a rule not prominent, whereas the centric hili are generally 

 very distinct (bean), although there are many exceptions (wheat, 

 barley, and others). 



5. Size. The variation in size is extreme. The smallest granules 

 occur in some of the spices (pepper, allspice) and in some of the grass 

 family (rice), whereas the largest granules occur in some of the palms 

 and in widely separated plant groups (Liliaceae, Solanaceae). 



6. Polariscopic Behavior. Under polarized light, two wedge-shaped 

 (tapering from the outer surface toward the hilum) bands appear 

 which always cross at the hilum, and the polarizer may be used for the 

 purpose of locating the hilum in those starches in which this structure 

 (or rather the absence of a structure) is indistinct. These bands may 

 be very marked (as in potato, corn, arrowroots) or quite indistinct 

 (wheat, ginger, barley). In isodiametric starch granules with centric 

 hili (corn, rice, pepper, cardamom) the cross bands are at right angles 

 to each other, whereas in elongated granules, bean, pea, and in the 

 starches with excentric hili, the cross bands are not right angled. 



The manufacture of commercial starches, or rather the obtaining 

 of commercial starch, is comparatively simple. The starchy material 

 (roots, stems, fruits, seeds, grains) is powdered or pulped, with or 

 without previous soaking in water, and the starch washed out of the 



