ROC CELL A. 



135 



Cape. Barbary or Mogador, and Madagascar forms are in- 

 ferior in size and quality. Besides R. tinctoria and R. fu- 

 ciformis, and the varieties hypomecha of the former and 

 linearis of the latter, the chief botanical sources of these 

 Orchella weeds are R. Montagnei, R. pygmcea, R. Jlaccida, 

 R. phycopsis, and R. dichotoma. Comparatively numerous 

 as are their geographical sources, many new and probably 

 superior fields of export remain to be opened up to British 

 commercial enterprise; in illustration of which we need 

 only cite the vast fields of India and the Indian Archi- 

 pelago, the shores of Africa and Asia bordering on the 

 Red Sea, New Zealand, New South Wales, and many of the 

 Pacific Islands. The Eoccellas grow abundantly on the 

 arid rocks of Aden, in Arabia ; and the Indian and Ceylon 

 specimens which we have seen are remarkable for their 

 great size."**" The production of an export trade in dye- 

 lichens might not only prove a boon to the poor inhabitants 

 of many a hitherto barren shore, but would probably become 

 remunerative to British manufacturers who are at present 

 paying high prices for the Angola weed and similar fine 

 varieties of Orchella-weed, which are fast becoming scarce 



* Vide Paper by the Author in the c Edinburgh New Philosophical Jour- 

 nal, ' July, 1855, on the "Dyeing Properties of Lichens/ 5 



