42 



The Present Range of Potamogeton crispus L. in North America 



L. R. Tehon 



The afternoon of August 24, 1928, while Dr. David H. 

 Thompson and the writer were engaged in a brief survey of 

 the aquatic plants making up the weedbeds of Lake Nippersink, 

 in Illinois, we picked up a fragmentary branch of Potamogeton 

 crispus. In the short time then at our disposal, we were not 

 able to make a thorough search for more of it; but as other 

 pondweeds, such as P. americanus, P. Richardsonii, P. compres- 

 sus, and P. foliosus, were obtained in abundance during the 

 afternoon, it is probable that P. crispus was not abundant 

 there. This small specimen, taken by chance, provides the only 

 record we have of the occurrence of the plant in that lake; 

 and it is, moreover, the only specimen of P. crispus that we 

 have obtained in Illinois waters, though during the past four 

 seasons we have collected in many places. 



This pondweed is considered to be an introduced species, 

 possibly of European origin; and both the manuals and the 

 monographs agree in assigning to it a very limited range in a 

 few East Coast States. The latest range, as given in Norman 

 Taylor's^ monograph of 1909 is from "Ontario to Delaware 

 and eastern Pennsylvania." As our specimen seemed, in con- 

 trast with this, to indicate a considerable westward extension, 

 I undertook to search out additional evidence of its spread, 

 both as recorded by specimens deposited in herbaria and by 

 printed observations. 



The earliest printed note on the range extension of the 

 species is by Dr. Morong,^ who inadvertently made it a matter 

 of record at the Buffalo meeting of the "American Association" 

 that P. crispus had occurred in Arizona. This was seven years 

 before the appearance of his monograph^; but in the monograph 

 itself he does not mention the Arizona instance, probably 

 because he supposed it to have been too rare and far removed 

 from the abundant range to be duplicated soon. 



1 North American Flora 17>: 21-22. 



^ Bull. Torrey Bot. Club 3: 171. 1886. 



» Memoirs of the Torrey Botanical Club 3\ 1893. 



