50 
The herbaceous associations of the prairie fall rather definitely into 
two types that appear to be caused by greater or less desiccation of the 
soils. The more xerophytic of these, of which Stipa comata, Avena Hookeri, 
and Koeleria cristata are characteristic or dominant species, is limited to 
the wind-swept, well-drained margin of the bluff that is just above the 
Figure 5. Map of vegetation in Peace Point district. 
