204. 



POPULAR HISTORY OP LICHENS. 



varieties are in their habitat montane or alpine, growing on 

 rocks, chiefly quartzose or granitoid, on many of our High- 

 land mountains, such as Ben Nevis and Loch-na-gar : from 

 the latter locality we have seen specimens of the common 

 variety and var. stygia in fine fructification. On tearing 

 across the lacinulae of any of the forms, it will be seen that 

 the medullary tissue is quite white, and that the very dark 

 colouring matter is confined to the cortical layer. In var. 

 tristis the spermogones may be observed roughening the 

 lacinulse, as in Ramalina scopulorum, with their rounded 

 tubercles ; they are globular, and open by an ostiole. The 

 spermatia are linear and straight. This species has been 

 said to yield a brownish or reddish colouring matter ; if so, 

 it must, at least, be of questionable utility. 



13. Parhelia aquila (aquilus, sun-burnt or swarthy). 

 Thallus chestnut-coloured, membranaceous-cartilaginous, 

 sometimes greyish -pruinose, — below paler, black-fibrillose ; 

 segments sinuate-lacinulate, imbricate, convex at centre, 

 explanate at periphery. Apothecia brownish-black; mar- 

 gin entire, thick. The thallus sometimes becomes crusta- 

 ceous and uniform, or subradiose at periphery. (E. B. 982.) 



A common species on rocks on or near sea-coasts ; it 

 is frequent on the Pentlands, Arthur's Seat, and at Caro- 



1 



