336 ANNUAL OF SCIENTIFIC DISCOVERY. 



nected water system from one end to the other. The plant was 

 introduced by scientific men into the Cam, and other places, originally 

 for experimental purposes, and is of such a nature that, clinging to the 

 bottoms of vessels or boats, it might easily inoculate other streams and 

 waters. 



In the case of the Cam, in the short space of four years, it multiplied 

 so, from a single stem, as to impede both navigation and drainage. It 

 has become a great and growino- evil : and the attention of scientific 



c* ^3 ^^ 



men of practical men is loudly demanded to the subject of its 

 extinction. 



DYE-LICHENS. 



In a paper lately read by Dr. Lindsay, before the Botanical Society 

 of Edinburgh, on " the natural history of the lichens," there are sev- 

 eral remarks on the commercial value of this widely-distributed class 

 of plants well deserving publicity; it being highly probably that, 

 were masters and supercargoes of ships awaie of the value of these 

 plants, which cover many a rocky coast and barren island, they might, 

 with a slight expenditure of time and labor, bring home with them 

 such a quantity of these insignificant-looking plants as would realise 

 considerable sums, to the direct advantage of themselves and the ship- 

 owners ; and consequently to the advantage of the State. It is with 

 the view of inciting those to whom the opportunity may offer of gath- 

 ering a valuable article of commerce, the value of which they would 

 little suspect from its external aspect, and of inducing the owners of 

 vessels to direct the attention of their officers to this subject, that I 

 subjoin some simple methods of detecting the varieties of lichens valu- 

 ble as dye-stuffs, together with a slight outline of this paper, so far as 

 it bears on the commercial aspect of the subject. Dr. Lindsay prop- 

 erly points out that it is not the lichens which themselves exhibit the 

 most beautiful red and purple colors which yield the finest and most 

 valuable dyes, but that the opposite rather obtains ; since it is those 

 which are devoid of any bright tint, the grey and ash-colored varie- 

 ties, which yield the greatest amount and most valuable descriptions of 

 dyes. In these varieties, of which orchil or orcella-weed of commerce, 

 the Rocella tinctoria of botanists, and the Lecanora tartarea or cudbear 

 are examples, the dyeing principles exist in the plant in a colorless 

 state ; nor do these mosses yield their beautiful tints until crushed and 

 exposed to the combined influence of the atmosphere, water, and 

 ammonia. To prove the frequency with which these lichens are met 

 with, and the wide extent of latitude in which they grow, the author of 

 this memoir points to an examination made by him of the raw vegeta- 

 ble products in the exhibition of 1851, amongst which he found speci- 

 mens of good dye-lichens from almost every part of the world, includ- 

 ing our own young colonies ; and he cites a note, affixed to a speci- 

 men of orcella-weed from Socotra, " Abundant, but unknown as an 

 article of use or commerce also abundant on the hills around Aden, 

 and might be made an article of trade." To show their value, he 



