The American Botanist 



VOL. XVIIl JOLIET, ILL., NOVEMBER, 1912 No. 4 



== LlBKJAl 



^EVV Y{ 



\jhe elm lets fall its leaves before the frost, BOTANIC 



Z/he very oafi grows shivering and sere; GAH.DE 



^/he trees are Barren ivhen the summer s lost, 



tXJut one tree keeps its goodness all the year. 



cfreen pine, unchanging as the days go Sy, 



C/hou art thyself, beneath ufhatever shy. 



— Augusta Webster. 



THE SUMMER FLORA OF THE CHICAGO PLAIN 



By Willard N. Clute. 



' I 'HE flora of the Chicago Plain is essentially a prairie flora. 

 -*■ In spring the relationship is somewhat obscured by the 

 occurrence of various species that can live in any moist soil, 

 but as midsummer approaches the strictly prairie species ap- 

 pear in ever increasing numbers until there is no mistaking 

 the character of the vegetation. The region, however, is not 

 a typical prairie. The soil is a deep and almost impervious 

 clay that was laid down as a soft mud in the bottom of a shal- 

 low lake that covered the region during the glacial period. 

 Upon the recession of the waters of the ancient lake, the plants 

 began to spread in from adjacent regions but the prairie spe- 

 cies appear to have been those best adapted to the plain and 

 they have held their ground ever since. 



The changes vxhich the region annually undergoes must be 

 rather trying to many species and have no doubt served to dis- 

 icourage the invasion of the area by plants adapted to other 

 situations. In the spring much of the surface reverts to its 

 primitive condition and becomes a series of shallow lakes, but 

 at the height of the growing season the other extreme prevails 



