18 BIG SPRING PRAIRIE. 



side-walks in the vicinity of the University of Chicago. 

 As another instance of this difference of habit, may be 

 mentioned Celtis occidentalis which, in Wyandot 

 County, Ohio, occurs chiefly on ridges or bluffs, while in 

 Illinois it is found only on the flood-plains of streams, as 

 on the flood-plain of the Das Plaines at Riverside. A 

 slight decrease in atmospheric humidity between two 

 places is often sufficient to limit to very narrow boun- 

 daries the habitat of certain species; which in the more 

 favorable localities have a wider range. 



Other common herbaceous plants of the Ridge 

 roadsides are Melilotus alba Desv. (White Melilot) : 

 Plantago lanceolata L,. (Ribgrass); Poa compessa Iv 

 (Wire-grass); Euphorbia (several species); Lithosper- 

 mum arvense L (Corn Gromwell, Wheat-thief); Trios- 

 teum perfoliatum L (Horse-Gentian); Solidago (various 

 species); Aster (various species); Achillea millefolium 

 Iv (Yarrow); Bidens and Carduns (several species). 



Polygala senega L (Seneca Snakeroot) is rarely 

 found on the ridges, and is one of the witnesses of 

 former plant societies. 



The most characteristic weed of wheat-fields is 

 Lithospermum arvense (Corn Gromwell. Wheat thief), 

 while Ambrosia (Ragweed), Amarautus (Pigweed) and 

 Chenopodium (Lambs-quarters) are also quite common. 



The region adjoining the prairie on the north and 

 west was covered with a typical mesophytic forest 

 formation of the Maple, Basswood, Beech type, with 

 its characteristic shrubs and herbs. 



2. Past Condition of the Prairie-historical 



FACTOR. 



On Sept. 17, 1818, a treaty was agreed upon be- 

 tween the U. S. Government aud the Wyandot In- 

 dians. One of the articles of this treaty reads as 

 follows: "That there shall be reserved for the use of 



