764 



BOTANY AND PHARMACOGNOSY. 



large, irregular aletirone grains 20 to 35 /a long, and- considerable 

 fixed oil. The easily separable seed-coat contains rather charac- 

 teristic stone cells, which on surface view are polygonal and pos- 

 sess rather porous, somewhat thickened walls and brownish-red 

 or brownish-black contents. Beneath the stone cells is a layer 

 of broad, irregularly-shaped cells with rather thick walls and 

 numerous intercellular spaces. 



I 



Fig. 307. Cinchona: B, bast fibers; Ca, cryptocrystalline crystals of calcium oxalate; 

 P, parenchyma containing few small spherical starch grains; E, sieve; K, cork. 



145. COCOA SHELLS. Little or no starch; oil globules; 

 characteristic, brownish, adhesive fragments, possessing more or 

 less hexagonal epidermal cells ; peculiar, small, tabular mucilage 

 cells and a layer of nearly isodiametric stone cells 10 by 10 /x, the 

 walls of which are 4 /a thick (Fig. 308). 



146. APOCYNUM. Dark brown (Fig. 202) ; sclerenchy- 

 matous fibers numerous ; fragments of laticiferous vessels yel- 

 lowish ; starch grains somewhat spherical, 7 to 15 ;U in diameter. 

 In Apocynum androscumifolium small groups of stone cells occur^ 



