168 BOTANICAL GAZETTE {MARCH 
feet above the country level, representing a lake bluff of the 
Glenwood stage of Lake Chicago.* This bluff has long had a 
mesophytic forest on its slopes, and yet it will be many centuries 
before the erosive forces remove all traces of this ancient sea 




FIG, 32.—Sea cliff at Glencoe, where lake erosion has been absent for a long 
period. Xerophytic trees and shrubs, especially conifers, dominate, e. g., white pine, 
red cedar, juniper. 
cliff. A still more striking case is to be seen north of Wauke- 
gan, where an ancient lake bluff, higher than that at Beverly 
hills and only a mile back of the present lake shore is tenanted 
by a high grade type of mesophytic forest. 
It will be instructive to make a few comparisons between lake 
bluffs and other plant societies. Closest to the lake bluff ina 
a and ALDEN: The geography of Chicago and its environs. Chicago, 
