References.—Report U.S. Commissioner of Agriculture, 1878, pp. 119 et seq.; Trimble, Am. Jour. of Pharmacy, p. 395, 1889; Canaigre, Bull. No. 7, Arizona Agr. Expt. Station, 1893; ‘Canaigre or Tanner’s Dock,’ Bull. No. 105, University of California, Berkeley, Cal.; ‘Canaigre Tannin,’ Trimble and Peacock, Philadelphia, 1893; ‘Report to the German Leather Trades Association,’ by V. Schroeder, 1894; ‘Il Canaigre,’ E. Andrieis, Turin, 1899.
Rumex maritima, or maritimus. Central Europe, England, Ireland. It is said by de Lof to be found in California, where it is used by the Indians for tanning; but he probably confounds it with canaigre. De Lof found its roots, wet, to contain 6 per cent. and after drying, 22 per cent. of tannin, together with starch and an acid allied to malic.
Several English docks contain tannin; the writer had a sample of leather tanned with dock-root (very possibly R. aquaticus), many years old, but still soft and close in texture, and of excellent quality.
Polygonum amphibium. Said to grow on thousands of acres (?) on the lower Missouri. Roots contain 22 per cent., branches 17 per cent. of tannin. P. amphibium is a common English and European plant, with spikes of pink flowers, growing in marshes and ponds. Probably this is the Polygonum analysed by Fraas, who found 20-26 per cent. tannin.
Polygonum Bistorta. Common in damp places in England. Bistort, Snakeweed, called “Eastermer giants” in Cumberland, where the young leaves are used for making herb-puddings. Fraas found 16-21 per cent. tannin in the roots.
Other species are known to contain much tannin. Perkin found a red colouring matter in P. cuspidatum, a native of India and China, commonly grown in gardens as a foliage plant (Journ. Chem. Soc., 1895, p. 1084). P. tinctorium, used as a source of indigo in China and Japan.
Coccoloba uvifera, Seaside Grape of West Indies; source of West Indian kino. Whole plant rich in tannin.
LAURACEÆ, Bay Family.
Persea, or Laurus lingue. Bark used in Chili for tanning Valdivia leather. (According to Arata, Laurus caustica.) A tree 25-30 feet high and 2 feet in circumference. Bark rough outside, and whitish, with an aromatic smell and taste, brittle and easily ground, contains 17-19 per cent. of a catechol-phloroglucol tannin, greening iron salts (Journ. Chem. Soc., 1881, p. 600). About 60,000 heavy hides are tanned yearly with this bark in Valdivia and district, and mostly sent to Hamburg. The hides are thick and scarcely tanned through, colour fair, leather soft and porous.
Persea Meyerina N. and Laurus Pneumo. Said to be also used in Chili.