Ferfiald : Notes on Potamogeton pensylvaniciis Cham. 375 



and puts a v. v. to it, in that he had seen Hving specimens, and 

 he refers to ' Fl. Danica ' t. 927, and Curtiss's ' Fl. Lond.', 5 

 1. 15. Specimens of crispits are extant in British Herbaria, 

 with dates c. 1832, ! 1841, ! 2nd 1842, ! and it is given by Kunth 

 in his Enum 3, 134, 1841, for 'America boreahs ' P. crispus 

 is distributed all over the world, but is very rare in S. America, 

 in the Argentine Republic (Maslock expedition). 







J»IOTES ON POTAMOGETON PEMSYLVANICUS CHAM. 



Prof. M. L. FERNALD, 

 Harvard, U.S.A. 



' Potamogeton epihydriim Rafin. (P. pensylvanicus Cham, 

 P. Claytoni Tuck) is one of the commonest, if not absolutely 

 the commonest species from the Gulf of St. Lawrence south- 

 ward, and there is hardly a pond or sluggish stream in the 

 Eastern United States where it does not grow. Consequently 

 its fruit could easily have got into manufactured goods at almost 

 any mill pond. But I cannot help wondering if your Yorkshire 

 plant may not be native. Here are my reasons : — There are 

 few if any clearly introduced Pondweeds. P. crispus is doubt- 

 fully native here, occurring very rarely away from the larger 

 settlements, and usually only in more or less artificial ponds. 

 Otherwise, I know of no introductions in America. 



■' Nearly all your Potamogetons of Great Britain are native 

 through the North Eastern United States and Canada, where 

 they are associated with P. epihydriim (P. pensylvanicus). We 

 have P. natans, polygonifolius, alpinus, heterophyllus, nitens, 

 lucens, zizii, praelongus, perfoliatus, crispus, acutif otitis, com- 

 pressus, obtiisifolius, pusillus, Friesii, nitiliis, pectinahis, fili- 

 formis, etc., and a few endemic species. Now, in my experience 

 in the field, I find very few of these species ascending to the 

 alpine ponds at the mouth of the River St. Lawrence ; but in 

 the alpine waters on Table-top Mt. (7250 feet) in Gaspi Co., 

 Quebec, there occur P. epihydriim and P. pusillus along with 

 Subiilaria aqiiatica and Sparganiiim^ angustifolium Michx (S, 

 affine Schnitzl.). The alpine plants of the adjacent bays and 

 ledges are circumpolar species, or, at least, plants of the colder 

 parts of Europe and adjacent Asia, such as Viola palustris, 

 Silene acaulis, Cerastium cerastioides, Sibbaldia procumbens, 

 Rubus Chamcemonis, Epilobium alpinum, Gnaphalium nor- 



1908 October i. 



