56 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



of the popped grains is due to the inclusion of air in the bursted cells. 

 During the heating the starch is converted into a soluble form, and 

 this gives popped corn its nutritive value. Some of the flint and 

 dent corns show a similar tendency to pop When heated, but it is 

 only in those parts of the endosperm that are horny and the cells of 

 which contain compactly arranged polygonal starch grains in which 

 the rarefied area is at least from one-tenth to one-fifth the diameter 

 of the entire grain. Pieces of the pop-corn, as well as the horny 

 portions of some of the flint and dent corns, will pop as readily as the 

 whole grains. 



(2) Zea Mays indentata yields the dent or flint corns, the grains 

 of which have a corneous (horny) endosperm on the sides and are 

 indented at the summit, owing to the shrinking of the cells, which 

 contain more cell-sap and less compactly arranged starch grains. 



The starch grains in the cells of the horny endosperm resemble 

 those of pop-corn, but the starch grains in the other cells are more or 

 less rounded or slightly polygonal, and vary from 0.005 to 0.025 mm. 

 in diameter; the central rarefied area is either wanting or usually not 

 more than 0.002 mm. in diameter. 



(3) Zea Mays saccharata yields the sugar corns. While the grains 

 are more or less translucent and horny, they have a wrinkled or shriv- 

 eled surface. The cells of the endosperm contain gum-like substances 

 and a relatively small number of nearly spheroidal starch grains 

 from 0.004 to 0.010 mm. in diameter. 



Corn Starch. This occurs as a fine, somewhat cream-colored, 

 mobile powder, which is practically free from cohering particles. 

 The starch grains (Fig. 20) are more or less polygonal or somewhat 

 rounded, usually with a distinct circular, or 2- to 5-rayed cleft in the 

 center, and vary from 0.010 to 0.035 mm. in diameter. When exam- 

 ined by means of the micropolariscope the grains show a distinct cross, 

 but the display of colors when the selenite plate is used is less pro- 

 nounced than in potato starch. This starch frequently contains 

 traces of alkalies, which may be detected by adding 0.5 gm. of the 

 starch to 2 c.c. ef an aqueous solution of fuchsin, when the latter is 

 decolorized. 



Corn Meal is whitish or yellowish, and in addition to the paren- 

 chyma which contains oil and characteristic starch grains there are 

 also present fragments of the pericarp. The latter are free from 

 hairs; the cells of the epicarp have thick walls with simple pores; 

 beneath the latter occurs a layer of parenchyma cells which are thin- 

 walled, more or less branching, between which are large intercellular 

 spaces; running at right angles across the branching parenchyma 



