54 



THE PLANT SOCIETIES OF 



something of a question. It seems likely that semi-xerophytic trees 

 will dominate there for a long time to come on account of the xero- 

 phytic atmospheric conditions. Particularly at the top of the bluff do 

 the conditions remain severe, by reason of the great exposure, and also 

 the dryness of the soil. If the lake should recede for some distance. 



Fig. 32.— Sea cliff at Glencoe, where lake eftision has been absent for a long period. Xero- 

 phytic trees and shrubs, especially conifers, dominate, «. g-., white pine, red cedar, juniper. 



a mesophytic forest could certainly develop on the bluff before it is 

 reduced to anything like the common level. This is shown on the 

 ancient lake bluff at Beverly Hills. Here there is an old cliff about 

 forty feet above the country level, representing a lake bluff of the 

 Glenwood stage of Lake Chicago.- This bluff has long had a meso- 

 phytic forest on its slopes, and yet it will be many centuries before 

 the erosive forces remove all traces of this ancient sea cliff. A still 

 more striking case is to be seen north of Waukegan, where an ancient. 



