The distribution of Potamogeton crispus 

 in North America 



Leo A. Hanna 



A short time ago an article in Torreya by Professor Leo R. 

 Tehon, Illinois State Natural History Survey, was read with 

 great interest by the writer. The article dealt with the range of 

 Potamogeton crispus in North America and presented a theory 

 that accounted for the extension of its range through the activ- 

 ities of certain aquatic birds. The evidence advanced seems 

 plausible indeed. That aquatic plants are transferred from one 

 situation to another by birds is unchallenged. 



It is also true that various pond weeds, of which Potamoge- 

 ton crispus is but an example, are often found far out of the range 

 of the ordinary routes of migration followed by birds. As an ex- 

 ample of such a case Mr. Tehon cites a station in Oregon from 

 which Potamogeton crispus has been reported. No doubt he can 

 add others. Dr. R. J. Gilmore of Colorado College and the 

 writer have collected it at stations in the Medicine Bow moun- 

 tains of Wyoming, viz. lakes Swastika and Irene near the Uni- 

 versity Camp. The writer is certain that he has observed it in 

 other situations on the Laramie Plains as well as in the moun- 

 tains. 



The general presence of Poa pratensis and many other "nat- 

 uralized" plants in all parts of the Medicine Bow mountains 

 as well as in other mountainous regions of the West leads the 

 writer to follow Dr. Aven Nelson of the University of Wyoming 

 and others who maintain that it is probable that some of the 

 species that are supposed to have been introduced into this 

 country are in reality indigenous to the Rocky Mountain region. 



It is possible that Potamogeton crispus has a much broader 

 range than many of us at first assumed. In fact, it may actually 

 be indigenous to parts of North America. 



University Camp, 



University of Wyoming 



