TORREYA 



May, 1918 

 Vol. 18 No. 5 



THE LOCAL DISTRIBUTION OF INTRODUCED SPE- 

 CIES NEAR DOUGLAS LAKE, MICHIGAN* 



By Henry Allan Gleason 



During the summer of 1914 Gleason and McFarland made a 

 study of the local distribution of introduced species of phanero- 

 gams in the vicinity of the biological station of the University 

 of Michigan.! It was then shown that less than half of the 

 introduced species had succeeded in establishing themselves in 

 the uncultivated region in the vicinity of the biological station 

 and that their number steadily decreased with increasing dis- 

 tance from civilization; that these introduced species were in 

 many cases dependent upon human aid for their dispersal; and 

 that they were unable to compete successfully with the native 

 vegetation. 



During the summer of 1917 these observations were continued 

 and in part repeated, in many instances in precisely the same 

 localities. The general conclusions of the earlier paper, as stated 

 above, are fully confirmed, while successive study of the same area 

 after a three-year interval has given opportunity to show the 

 present course of development in the introduced vegetation and 

 among the introduced species. 



I. The Introduced Flora of Summer Resorts 

 The reduction in the number of introduced species with in- 

 creasing distance from agriculture or permanent residences is 



* Publication no. 171 from the Botanical Department of the University of 

 Michigan. 



t H. A. Gleason and F. T. McFarland, The introduced vegetation in the vicinity 

 of Douglas Lake, Michigan. Bull. Torr. Club 41: 511-521. 1914- 



[No. 4, Vo.. 18 of ToRREYA, comprising pp. 65-80, was issued 8 May, 19 18.] 



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