INDIA-RUBBER 393 



contains no stereids, but is made up of strands of more or less col- 

 lapsed sieve cells; cambium zone is distinct; the wood consists of 

 medullary rays from 1 to 2 cells wide, separating the narrow wedges 

 of xylem, the latter being mostly made up of wood parenchyma, a 

 few wood fibers and occasional tracheae ; the primary vessels are still 

 to be observed in the center of the stele ; the bast fibers are very irreg- 

 ular in outline, more or less tuberculated, the walls being strongly 

 thickened ; calcium oxalate may occur in the form of rosette aggregates. 



Powder. Pinkish-brown or light reddish-brown; starch grains 

 numerous, from 0.005 to 0.035 mm. in diameter, mostly single, 

 spheroidal, ellipsoidal, of variable shapes, and usually with a central 

 cleft; fragments, with more or less tabular secretion cells containing 

 a reddish-brown, amorphous, resinous substance; trachea mostly 

 with simple pores and associated with wood fibers, the walls being 

 very thin, lignified and possessing numerous, transverse slit-like, 

 simple pores and swelling perceptibly in potassium hydrate solution; 

 bast fibers long, narrow, the walls thick and slightly lignified; frag- 

 ments of reddish-brown cork cells; occasionally rosette aggregates of 

 calcium oxalate, about 0.035 mm. in diameter. 



Constituents. A volatile oil, with the odor and taste of the root, 

 from 3 to 4 per cent; an acrid resin sylvacrol; an acrid fixed oil; 10 

 to 12 per cent of -tannin; starch; calcium oxalate; ash about 5 

 per cent. 



Literature. Holm, Merck's Report, 1911, p. 36; Miller, Brooks 

 and Rutledge, Jour. A. Ph. A., 1915, 4, p. 445. 



ELASTICA. Caoutchouc, India-Rubber. The latex or milk- 

 juice of Hevea braziliensis, and probably other species of Hevea 

 (Fam. Euphorbiacese), trees indigenous to Brazil. The milk-juice is 

 obtained by making incisions in the bark of the tree and is collected 

 in small cups fastened to the trees. This is then poured into a larger 

 vessel in which is placed a wooden paddle. The latter, with adhering 

 latex, is dexterously revolved in an open fire until coagulated, new 

 material being added from time to time until flask-shaped masses 

 are formed which are then removed, and constitute the commercial 

 article known as " bolacho." The best grade, known as Para 

 Rubber, is official. 



Description. In elastic, flask-shaped masses or pieces varying in 

 form and size; light, floating on water; externally brownish to 

 brownish-black; internally brownish, consisting of a number of thin, 

 alternate light and dark layers, due to the superimposed coats of 

 latex formed during the drying process; odor slight, empyreumatic; 

 nearly tasteless. 



