-64- 
As pointed out bofor \ there are two points on the talus 
where soil first begins to accumulate, namely, the bottom 
of the slope along tho margin of tho forest and the very 
top - at the foot of the asoarprient• Host of that at the 
top is due to fine material v/hioh is washed over from the 
summit and hold in place. This finer soil, coupled with 
the shadier conditions directly under the cliff, gives 
rise to a narrow strip of vegetation composed of a complex 
of spool os, some pioneer and some more or less mosophytic 
in char actor, -among the more important of these are Plnus 
atrobus . Plnus resinoSc . Quercus rubra t Prunus pennsylvonica . 
fopulus trenuloidos , Coanothus americonns , ?sodora quinque - 
folia, Rhus Toxicodendron , Oornus circinata . Khus typhina . 
Oolastrus scandens , Ostrya virgin!ana , Arctostaphylos Uva - 
ursi , and Symphorioarpos racomosus Miohx. var. pauciflorus 
Robbins. This plant assemblage, especially as regards the 
more mesophytic species, is only temporary, for as tho cliff 
recedes, the vegetation must recode with it. As tho height 
of the cliff becomes less, tho increased light and lessened 
degree of moisture make conditions intolerant for the more 
mesophytic si)ecies. Finally, with the disappearance of the 
escarpment, only xerophytic species are able to endure, 
such as occur on the more exposed portions of the smaller 
talus slopes. The border of tho forest forms a tension 
