GROUP I. THALLOPHYTA : FUNGI: LICHENS. 



323 



FIG. 230. A A fruticose Lichen, Usnea barbata, with apothecia, a. 

 Lichen, Sticta, pulmonacea, with apothecia, a (nat. size). (After Sachs.) 



JB A foliaceous 



Bmomycrs rufits is common on 

 sandy soil : the Verrucariese, the 

 Pertusariese, etc. 



Many species of crustaceous 

 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- 

 tbering of the rocks and to the 

 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 JB 

 Graphis elegans: V slightly magnified. C Per- 

 tusaria Wulfeni, slightly magnified. (After 

 Sachs.) 



