LICHENS; a family of plants, belong ing to the class cryptogamict, containing about 1400 known species, are under sev eral genera. Their substance is powdery, crustaceous, membranous, coriaceous, or even corneoua. They are common every where, adhering to rocks, the trunks of trees, and barren soil. On ascending mountains, they are found flourishing be yond the limit of all other plants, even to the verge of perpetual snow. Many of them, fixing upon the hardest rocks, by retaining moisture, facilitate their decom position and promote the formation of soil. Several of the species are used for sustenance in times of scarcity, by the in habitants of the northern regions.
Iceland moss is exceedingly abundant in the arctic regions, and often affords aliment to the inhabitants either in the form of gruel or bread, which last is very nutritious. The taste is bitter, astringent, and extremely mucilaginous. It is fre quently employed in pharmacy, in the composition of various pectoral lozenges and syrups, and is celebrated as an arti cle of diet, in combination with milk, in coughs and pulmonary affections.
Orehil (rocella tinetoria) is also an im portant article, though less used now than formerly, on account of the fugitiveness of the rich purple and rose-colored dyes which it yields. Some of its tints, how
ever, are capable of being fixed, and it is, besides, employed for staining marble, forming blue veins and spots. Several other lichens afford dyes of various colors, as litmus.
Lichen, Liverwort, or Algae, are the stunted herbage of the arctic circle, and of barren heaths. In Iceland and Lap land, it is eaten in broth and milk, and even made into bread, its bitterness be ing removed by washing in hot waters. It contains much mucilage or gluten, and has been extensively used in pulmonary complaints, and as a demulcent, relieving cough, and correcting all acrid secretions.
Lichen, Orchil, or Argot, alluded to above, is famous for its dye of purple, blue, violet, (tc. It is mostly brought from the Canary Isles, and is there ground in a mill, mixed with pearl-ash and urine, and sold in cakes. It is used to heighten colors, but is very evanescent, except when used with a tin solution, which gives to it a per manent red dve.