CHICAGO AND VICINITT. 



53 



A. laevis, Equisetum hyemale (Scouring rush), various grasses, etc. 

 Soon there develops a xerophytic thicket vegetation, such as is shown 

 \nfig. 31. This may be called the shrub stage of the captured cliff, and 

 among the dominant species are the juniper and cedar {/uniperus 

 communis and J. Virginiand), Salix glaucophylla (Glaucous willow), the 



Fig. 31.— Sea cliff at Glencoe, at a place where lake erosion has ceased. Shrubs (largely 

 cedars and willows) prominent as well as herbs. Absence of lake erosion also indicated by the 

 gentle slope, as compared with fie-So- The leaning oak at the top bears witness to former 

 erosive forces. 



osier dogwood {Cornus stoloniferd), Shepherdia Canadensis, various 

 sumachs {Rhus typhina and R. glabra). The following tree stage is 

 dominated by various poplars {Populus tremuloides, P. grandidentata, 

 F. moniliferd), the hop hornbeam {Ostrya Virginica), the white pine 

 {Finns Strobus), the red cedar {Juniperus Virginiana], and some of the 

 oaks (probably Quercus rubra and Q. coccinea tinctorid). Fig. 32 

 shows a tree-clad cliff in which most of the above trees are to be 



found. 



Whether a mesophytic forest would develop on a lake bluff is 



