ORCHILLA WEED, the commercial name applied to several species of Rocella (Nat. Ord. Lichenes). The most common is R. tinctoria, De Cand., which, although found growing on the rocks of European coasts even as far north as Britain, is chiefly collected on the tropical coasts of Lima and Angola. From the same localities, and also now in considerable quantities from India, R. fuciformis is also collected and exported. These are often mixed with other species, as R. dichotoma, R. pygmaea, R. flaccida, &c. These lichens are foliaceous, branched like a stag's horn, but generally flat. Their colour is a greenish-gray; and they have a peculiar and agreeable odour, resembling primroses, when in large quantities. When reduced to a pulp, and mixed with an ammoniacal liquor, they yield, after macera-
Orchomenus and fermentation, a beautiful purple colour, which is called orchil or archil. Beckmann (History of Inventions) narrates the accidental discovery of the colouring properties of this plant by a Florentine merchant, which serves to explain the fact that this rich dye was so long a secret, known only to the Florentines. It is more than probable, however, that the Phycos thalassion of Theophrastus and Dioscorides, used in their time for dyeing wool, and collected for that purpose in the Greek islands, was one of the species of Rocella. This dyeing material varies very much in price. It has been sold as high as L.1000 per ton; but it now ranges from L.30 to L.70. The quantity imported in 1857 was 998 tons, the greater part of which was from Portugal and Lima. (r. c. A.)