GROUP I. THALLOPHYTA : FUNGI: LICHENS. 



323 



Fis. 210. .A A fruticose Lichen, TTsnea barlata, with apothecia, o. 

 Lichen, Stictj. pulmonacea, with apotheoia, a (nat. size). (After Sachs.) 



B A foliaceous 



Bccomyces rufits is common on 

 sandy soil : the Verrucariese, the 

 Pertusarieae, etc. 



Many species of crustaceons 

 Lichens inhabit the highest 

 peaks of the Alps, and other 

 lofty mountains, on which there 

 is no other vegetation, and they 

 contribute materially to the wea- 

 thering of the rocks and to tlie 

 formation of a vegetable soil. 

 When they grow on the trunks of 

 trees, they occur more especially 

 upon those which have a smooth 

 surface ; the formation of a rough 

 bark seems to interfere with their 

 growth. Lichens may become 

 completely dried up without los- 

 ing their vitality. 



FIG. 231. Crustaceous Lichens. A and B 

 Graphis elegans: B slightly magnified. C Per- 

 tusaria Wulfeni, slightly magnified. (After 

 Sachs.) 



