PAPERS ON BOTANY 123 



AN ECOLOGICAL SURVEY OF THE VEGETATION 

 OF THE ILLINOIS PRAIRIES— A PRE- 

 LIMINARY REPORT 



Homer C. Sampson, University of Chicago 



During the summer of 1915 the writer made a study of the 

 associations of prairie plants occurring upon the relic virgin 

 prairie tracts throughout the state. The work was conducted 

 through the aid of the State Natural History Survey, and 

 under the direction of Dr. Henry C. Cowles and Dr. George 

 D. Fuller. The locations of the areas studied were obtained 

 through ahe aid and courtesy of the county surveyors. Among 

 the tracts visited and found to be in a sufficiently undisturbed 

 condition to warrant further study are the flood plain and 

 sand prairies along the Mississippi River between Ebner and 

 Savanna and at Hanover, sand prairies in the valley of the 

 Green River in Bureau and Henry counties, morainic sloughs 

 near Lacon and Camp Grove in Marshall county, numerous 

 prairies on the outskirts of Chicago on the old lake bed of 

 Lake Chicago, and a few small areas in Jasper and Clay coun- 

 ties. Old fence-rows and railway rights-of-way were also 

 considered after the survey had advanced sufficiently to indi- 

 cate their limitations. A detailed account of the locations of 

 these prairies and other less promising ones will appear in a 

 later publication. 



At the time of this report the data at hand seem sufficient 

 to allow the formulation of the following tentative conclu- 

 sions : 



1. The virgin prairies of Illinois exhibit definite associa- 

 tions of prairie plants. These associations are related in a 

 definite way to definite types of topography and soil condi- 

 tions which range all the way from such pioneer habitats as 

 clay, sand and swamps, to the well-drained soil of the upland 

 prairies. 



2. The development of the physiography of these pioneer 

 habitats is followed by dynamic successions of the plant asso- 

 ciations. The associations in these successions differ in 

 each particular case according to the initial habitat, but in all 

 cases they ultimately lead to a common type of climax prairie. 



