Buckthorn
the English name of rhamnus, a genus of plants, the typical one of the order rhamnacex (rhamnads). The berries of the common species are black, nauseous, and, as the specific name rhamnus catharticus imports, highly cathartic; they afford a yellow dye when unripe, as the bark of the shrub does a green one. They are sold as French berries. The alder buck- BUCKWHEAT thorn, again, has dark purple purgative berries, which, in an unripe state, dye wool green and yellow, and when ripe bluish gray, blue, and green. The bark dyes yellow, and, with iron, black. Of the foreign species, the berries of the rock buckthorn, or R. saxatilis, are used to dye the Maroquin, or Morocco leather, yellow, while the leaves of the tea buckthorn, R. thezans, are used by poor people in China as a substitute for tea. The species best known to the pharmacopeia of this country is the R. purshiana, otherwise called cascara sagrada.