TORREYA 



Vol. II 



October, 1911 



No. 10 



A BOG IN CENTRAL ILLINOIS* 



By Frank C. Gates 



At the headwaters of Lake Matanzas, a bayou of the Illinois 

 River in Mason County, Illinois, about forty miles south of 

 Peoria, is situated a bog which the writer visited during July, 

 1910. The bog is of interest because it is so far south of the 

 usual southern limits of peat-bog plants, as outlined by Tran- 

 seau.f In it occurs a curious mixture of swamp, bog, and 

 mesophytic plants. The many attempts to separate swamps 

 and bogs by purely physical factors have always virtually proved 

 futile. The plants themselves are the indices and there need be 

 no difference in the environmental factors. 



The bog proper is an area, 0.04 of a square mile in extent, in 

 which the soil is a water-soaked muck, imperfectly drained 

 towards Lake Matanzas. The drainage lines are indicated during 

 the summer by small creeks, without open water but hidden by 

 very dense growths of Leersia oryzoides. Occasionally a few 

 plants of Cinna arundinacea accompany the Leersia. This asso- 

 ciation ends abruptly at the edge of the running water. (Fig. i.) 



The historical factor has the greatest weight in accounting 

 for this bog, for it is known that in times past central Illinois 

 was vegetated by northern plants. Following the retreat of 

 the glaciers this northern vegetation has been displaced by 



* Contributions from the Botanical Laboratory of the University of Michigan 

 No. 128. Submitted with the spelling in accordance with the recommendations 

 of the Simplified Spelling Board, and changed to conform to the editorial policy 

 of TORREYA — N. T. 



t Transeau, E. N. "On the Geographic Distribution and Ecological Relations 

 of the Bog Plant Societies of North America." Bot. Gaz. 36: 401-420. 1903 

 (with a map). 

 |No. 9, Vol. II, of ToRREYA, Comprising pp. 1S1-204, was issued 12 Sept. 1911.] 



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