152 



POPULAR HISTORY OF LICHENS. 



elm, fir, and other trees in some of our Highland forests ; 

 it is however seldom or never met with in fructification in 

 Britain, though it is not unfrequently found fertile in Switz- 

 erland. Its thecse are small; its spores small, oval or 

 globular, colourless, and double-walled, resembling those of 

 Usnea and Cornicularia. It yields readily to boiling water 

 and other solvents a beautiful yellow colouring matter, which 

 has been employed in domestic dyeing by the Swedes. It 

 once enjoyed celebrity as a specific in jaundice, probably on 

 the similia similibus principle, from some fancied connection 

 between its colour and that of the skin in this troublesome 

 disease. 



3. Cetraria nivalis {mar, nivis, snow). Thallus straw- 

 coloured on both sides, frequently of a deep yellow at the 

 base, ascending, membranaceo-cartilaginous, deeply reticu- 

 late-lacunose or channeled, sinuate-lacerate-lacinulate ; mar- 

 gins crisped, sometimes black -denticulate ; surface of thallus 

 sometimes sprinkled over with white soredia. Apothecia 

 (which are very rare) yellowish-flesh-coloured, terminal, 

 having a thalline, crenulate margin. (E. B. 1994.) 



A somewhat common alpine and subalpine species, grow- 

 ing on the ground on the summits of our Highland moun- 

 tains, such as Ben Lawers and Cairngorm. In Britain it 



