The native country of flax is unknown, though supposed to be derived from Egypt, or from Central Asia. It has been known from remote antiquity (see Gen. xli, 42, and Exod. ix, 31). It is now naturalized in nearly all civilized countries. It blossoms from May to August, and matures its seeds early in autumn. The seeds and their expressed oil are used in medicine. The seeds are described by the U. S. P. as follows:
“About 4 or 5 Mm. (⅙ to ⅕ inch) long, oblong-ovate, flattened, obliquely pointed at one end, brown, glossy, covered with a transparent, mucilaginous epithelium, which swells considerably in water; the embryo whitish or pale greenish, with 2 large, oily, plano-convex cotyledons, and a thin perisperm; inodorous; taste mucilaginous, oily, and bitter. Ground linseed (linseed meal, or flaxseed meal), for medicinal purposes, should be recently prepared, free from unpleasant or rancid odor. When extracted with carbon disulphide, it should yield not less than 25 per cent of fixed oil. The filtered infusion of ground linseed, prepared with boiling water and allowed to cool, has an insipid, mucilaginous taste, and should not be colored blue by iodine T.S. (absence of starch)”—(U. S. P.). In this connection see paper by J. U. Lloyd, on the testing of flaxseed for starch, in the Pharm. Rundschau, 1895, p. 210.
Oil-cake (cake-meal, when ground) is the compressed refuse portion remaining after the oil has been pressed out; it contains the mucilage of the husk and all of the nitrogenous matter of the seed in condensed form (about 5 per cent nitrogen), and is therefore used to feed cattle. Starch should be absent from the cake, and the ash should not exceed 5 per cent. The seeds finely ground, furnish a dark, ash-colored powder, flaxseed meal, which forms with hot water a tenacious substance, used for luting in chemical operations. For poultices, the official Ground linseed (Farina lini, or Linseed meal) is the best.