BOTANICAL SURVEY— SUGAR GROVE REGION 



277 



action of the wind and to the greatest extremes of teiuperature, together 

 with the most sudden changes which are possible within the limits set 

 up by the climate of the region. The flora is of the sort that has gen- 

 erally passed as xerophytic, but in reality it may not be so much xero- 

 phytic as oxyphytie. It bears little resemblance to the truly xerophytic 

 flora of desert regions. 



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Fig-. Ki 



The Miiiiiiluif Tundra at the Edge of the 1' 



The vegetation of the cliff tops develops into zones similar to those 

 found around ponds, but in this case the zones depend on the depth of 

 the soil and the exposure. The front rock is nearly bare, but supports a 

 few foliose lichens (Parmelia sp.), a few small mosses seldom found in 

 fruit, with occasional stunted stragglers fi'om the next zones. 



The outermost zone of vegetation is the lichen formation. It ex- 

 tends from the bare rock back until the soil has reached a depth of 

 about a decimeter, when it gives way to the Vacciniuin zone. The 

 characteristic plants are : 



Cladonia spp. 

 Polytricum spp. 

 Lechea minor 

 Panicum sphaerocarpon 



Car ex (two or three species, in- 

 cluding C. triceps.) 

 Houston ia Jon fli folia 



There are also numerous waifs from other associations. On this 

 account the composition of the zone varies greatly from place to place 



