122. CANAIGRE.—The root of Ru'mex hymenosep'alus Torrey, from which a tannin is obtained. This plant resembles common dock, Rumex crispus, and flourishes in dry, barren, sandy soil in Southwestern United States and Mexico. It propagates by means of the roots, which grow in clusters of three or four. They are from 50 to 150 mm. (2 to 6 in.) long, and 25 to 50 mm. (1 to 2 in.) thick, reddish-brown to almost black. A cross-section shows a prominent cambium line and a broad radiating center. The tissue is chiefly parenchyma, containing starch, tannin, and a yellowish-red coloring matter. The tannin is yellowish-white, identical with that of rhubarb (rheotannic acid).