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TEXTBOOK OF BOTAiNY 



Fig. 253. Rock tripe (Gijrophora) a foliose lichen on a sandstone cliflF. The 

 smaller lichen (lower left) is the toad-skin lichen {Umbilicaria) . Photo by R. T. 

 Wareham. 





Fig. 254. A plant community of lichens, mosses, and other small plants; pioneer 

 vegetation with consequent soil formation and accumulation on rock substrates. 

 Photo by C. H. Jones. 



