24 OJf THE MEDICINAL AND TOXICOLOGICAL 



Certraria nivalis, Acli. ] Snow Cetraria. White Mts. and* 



Lichen " Linn. ) ISTortliwards. 



This may be nsecl as a substitute for the C. Islandica. Lind., 

 jS'at. Syst. 329. The powdered plant is said to act as a specific in 

 hydrophobia. Merat. & De L. 



Hocella tinctoria, De Cand. \ Dyer's Rocella. Kock moss, 

 Lichen rocella, Linn. f or archill. On maritime rocks. 



"This interesting lichen is the famous archill, or orchill — 

 Orseille of the French — which yields the most valuable dye of all 

 this tribe." It derives its name from a Florentine family, one of 

 whom, in 1300, carried on a considerable trade in it, and who- 

 first made known in Europe its valuable properties. The Canary 

 Islands formerly yielded it, and it was called Canary weed. So 

 great has been its consumption of late, that the best cpiality of it, 

 whose average price is £200 the ton, has become extremely 

 scarce ; and what is commonly imjjorted from other countries is 

 not worth £30 the ton. "The English blue broadcloths are first 

 dyed with archill, which gives their peculiar luster, and jDui-ple 

 tint when viewed in a certain light." C. of England ; Lind., l»5"at. 

 Syst. 329. According to an analysis of ISTees, it contains a brown 

 resin, wax, glutinous matter, insoluble starch, gummy matter, 

 lichenin, tartrate and oxalate of lime, and chlo. of sodium from 

 the adherent sea-water. Dr. Kane, in the Phil. Trans., 1840, 273, 

 has instituted a still more elaborate investigation. Among the 

 products is a substance called rocelline. The coloring matter is 

 Enjthnne. Litmus was formerly procured from this plant. 

 Blue orchill is procured by steeping the lichens in an ammoniacal 

 liquor, in a covered wooden vessel. Eed orchill is made with the 

 same liquor in common earthen jars, placed in a room heated by 

 steam. Pereira, M. M. ii. 42 ; Tliompson's Org. Chem, 284 ; 

 Nees and Ebermaier, Hand. i. 49. It was formerly an article of 

 some commercial importance, was Avell known t(i the ancients 

 (Pliny, xxvi. c. 10) ; the secret source of their purple dye was lost 

 till, in 1300, a merchant of Florence discovered that urine com- 

 municated to the plant a beautiful violet color; the knowledge of 

 this was confined to tliis country and to Holland. Bancroft on 

 Philos. of Color, p. 282. M. lioluquet found in the plant a sweet 

 substance susceptible of crystallization. Journ. de Pliarm., xv., 

 298 ; M. & De L., Diet, de M. M. The tincture is employed to 

 prevent the itching which exists in tlie throat in some coughs. 

 Coxe's Am. Disp., 368. M. De Candolle says that in the Isle of 



