The American Botanist 



VOL. XVII 



JOLIET, ILL., AUGUST. 1911 



No. 3 



THE FLORA OF THE CHICAGO PLAIN. 



By Willard N. Clute. 



' I ' HE City of Chicago is located on a nearly flat stretch of 

 •*■ country, at the head of Lake Michigan, known as the 

 Chicago plain. This plain is from ten to to fifteen miles in width 

 and once formed part of the floor of a great glacial lake a rem- 

 nant of which still exists as Lake Michigan. Westward and 

 southward the plain is bounded by a broad belt of intermingled 

 sand gravel and clay known as the Valparaiso moraine which 

 formed the shore of the ancient lake at this point, and was, in 

 fact, largely the cause of it, since it held back the waters of the 

 nielting ice sheet until they found a way out by way of the 

 "sag" and the Desplaines valley into the Mississippi. 



At present the plain averages about twenty feet above the 

 surface of Lake Michigan, but it still bears evidences of its re- 

 cent and watery origin in extensive stretches of marsh-land 

 and general lack of drainage. In the parts that have not been 

 artificially drained the few inhabitants regard the rubber boot 

 season as a natural condition to be accepted with the same for- 

 titude that summer drouth and untimely frosts are endured. 

 During the spring rains, extensive "wet weather lakes" may be 

 formed over large tracts that are dry enough in summer to 

 produce a fair crop of hay or in some instances garden crops, 

 but which at this season are impassible to one ordinarily shod. 

 The soil is almost exclusively a deep and impervious clay, 

 though darkened by the decaying vegetation that for many 

 centuries has grown upon it. Here and there one finds sandy 

 ridges or mounds which mark the location of ancient lake 

 beaches, or of shallows in the lake itself. These are covered 



