INTEODUCTION TO CRYPTOGAMIC BOTANY. 385 



Sticta pulTTionaria, and probably several other species; but 

 these are of little comparative importance. The purple and 

 blue are of much greater consequence, the former of which 

 is obtained largely in this country under the name of Orchil and 

 Cudbear ; while the latter is manufactured in Holland under 

 the name of Litmus. The kinds which are principally used are 

 Roccella tinctoria and fuciformis ; certain allied species or 

 varieties of these Lichens ; together with a few species which 

 have a more depressed habit and pass under the name of moss. 

 The Angola weed, however, Roccella fuciformis, is employed 

 now almost exclusively, as being the best, and at the same 

 time the most economical. The colouring matter is known 

 under the name of Orchil. Lecanora parella was once largely 

 gathered in Scotland, and the gathering, though a tedious pro- 

 cess, afforded employment to many in the Highlands.* It is 

 now obtained principally from Norway and Sweden, for the 

 London market, the manufacture being principally in the 

 hands of the English. The colouring matter which gives a 

 purple tint to woollen yarn is known under the name of Cud- 

 bear, from the Christian name of the gentleman, Dr. Cuthbert 

 Gordon, who first introduced it at Glasgow. It is, however, 

 fugitive. In the preparation of Litmus, potash or soda is used, 

 and by their use any Lichen which yields Orchil will produce 

 Litmus. Litmus is of great importance, as affording one of the 

 most delicate tests for acids, and is much used under the name of 

 Blue Test Paper, which acquires a red tint by the slightest 

 application of an acid. Other tests of less general use are 

 afforded by these Lichens ; and it is to be remembered that a 

 variety of different substances, of different chemical characters, 

 and economical importance, are obtained from them; a full 

 description of which is of interest only to the chemist and 

 manufacturer. 



426. Dr. Lindsay has lately been calling the attention of 

 the Botanical Society of Edinburgh to the importance of the 



* A person could earn about fourteen shillings a week by collecting 

 it. In some parts of North Wales it is particularly fine and abundant, 

 and used to fetch about three-halfpence a pound. 



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