ArticIvE III. — The J'egctation of the Inland Sand Deposits of 

 Illinois. By Henry Allan GeEason. 



Introduction* 



In the rapid development of ecological and phytogeographical 

 knowledge during the past few decades, the vegetation of sand de- 

 posits has been the subject of especially frequent and detailed study. 

 At least three reasons may be mentioned why this type of vegetation 

 has received particular attention. First, sand deposits are usually 

 well developed and form dune complexes of greater or less extent 

 along the shores of the ocean or the larger inland lakes, and in many 

 cases are convenient places for vacation trips. Secondly, the vegeta- 

 tion on sand is usually open and easily studied, and the dynamic na- 

 ture of the environment is emphasized. For this reason the inter- 

 relations of plant and environment are more easily observed and offer 

 attractive fields for study. Thirdly, sand areas are usually infertile in 

 comparison with their surroundings. They are accordingly fre- 

 quently left uncultivated and constitute temporary natural preserves, 

 in which the original types of vegetation persist and are available 

 for study. 



In the case of the inland sand regions of Illinois the first state- 

 ment is hardly effective, and that may explain why they have received 

 relatively little attention from local botanists. At the present time, 

 however, the}' comprise the larg^est, and virtually the only, areas of 

 natural vegetation within the state. With the exception of parts of 

 the sand deposits, of some small swamp areas, of rock outcrops, of 

 ponds and lakes, and of some small tracts of forest, all the original 

 vegetation of Illinois has been destroyed or greatly modified by clear- 

 ing, planting, or pasturing. The area covered by the last four of 

 these exceptions is very small, but there are still thousands of acres 

 of sand deposits in nearly original condition and available for study 

 They still contain some virgin prairie that has never been plowed or 

 pastured. These prairies are probably somewhat different from the 

 more representative types of prairie which fomierly grew upon more 

 fertile soil, but they are much more nearly typical than the small 

 strips still occurring along the margins of some streams and ponds. 



* The field work upon which this article is based, was carried on by the 

 aid of a grant from the Botanical Society of America. Further financial assist- 

 ance was given by the Illinois State Laboratory of Natural History. 



