TORREYA 



August, 1913. 

 Vol. 13 No. 8 



THE RELATION OF FOREST DISTRIBUTION AND 

 PRAIRIE FIRES IN THE MIDDLE WEST* 



By Henry Allan Gleason 



In a previous paper (1912),! referring to the location of certain 

 isolated groves in central Illinois, it was shown that they were 

 uniformly situated on the eastern side of prairie sloughs, and 

 the conclusion was advanced that their existence in these places 

 was due to the protection against prairie fires furnished by the 

 water barrier. Since the publication of this paper, a number 

 of similar facts have come to hand, all serving to indicate the 

 efficiency of ponds or streams in protecting forests from the 

 incursions and destructive effects of prairie fires. In general 

 it may be said that the location of forests throughout central 

 and northern Illinois, and also through the adjacent states, 

 is closely correlated with prairie fires. 



It is well known that the prevailing winds throughout most 

 of the Middle West come from the west, varying from northwest 

 to southwest. Prairie fires would, therefore, in most cases travel 

 toward the east, and would attack the forest on the west side. 

 Doubtless there were frequent cases where fires were driven 

 in other directions, but these must have been of vastly less impor- 

 tance than the very numerous fires travelling toward the east. 

 In the different descriptions of prairie fires which have been 

 consulted, and in the information furnished by eye-witnesses 

 of them, there is no specific mention of fires travelling in any 

 direction except east. 



* Contribution No. 141 from the Botanical Laboratory of the University of 

 Michigan. 



t Henry Allan Gleason, An isolated prairie grove and its phytogeographical 

 significance (with two figures). The Botanical Gazette, vol. 53, pp. 38-49. 

 Chicago, 1912. 



[No. 7, Vol. 13, of ToKREYA, comprising pp. 151-172, was issued 8 July 1913.] 



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