RAMALINA. 



143 



to twelve inches. From the Isle of May in the Firth of 

 Forth we have seen it in abundant fructification, of great size 

 and very tough, leathery consistence ; while in various other 

 localities we have gathered it plentifully in a delicate fili- 

 form state ; between these conditions there is every variety 

 of form and size. The cortical layer is extremely dense and 

 horny ; and, being devoid of distinct cellular structure, it ap- 

 pears like a hardened epidermiform excretion on the surface 

 of the plant. The medullary filaments towards the periphery 

 have very thick walls, the central canal being nearly oblite- 

 rated ; in the centre they have more of their ordinary cha- 

 racters. Its spermogones are frequently so numerous as 

 to roughen the thalline lacinise with the little tubercles of 

 which they consist. Each of these has a central blackish point 

 — the ostiole ; its cavity is almost spherical, but divided 

 into several compartments ; the spermatia are acrogenous 

 and oblong. These spermogones are liable to be confounded 

 with the perithecia of a small, black, punctiform Fungus, or 

 with the spot-like rudiments of a minute SpAceria. This 

 species has a somewhat wide geographical range, and occurs 

 as far south as the Falkland Islands and Kerguelen's Land. 

 It has been used to yield a red dye ; so high an opinion did 

 Lightfoot form of its tinctorial qualities, that he spoke of it 



