348 On American Species of the Genus Potamogeton. 



the surface of the water and floating, from membranaceous at 

 length more or less chartaceous-coriaceous, not attenuate at base, 

 broad- or ovate-elliptical, with very commonly a cordate base and 

 an obtuse and more or less distinctly mucronate tip, many-nerved, 

 often about 2£ inches long by nearly If wide ; the footstalks 

 slightly concave above. Stipules elongated, acute. Peduncles 

 nearly equal, shorter than the leaves. Nutlets rather large, ob- 

 liquely a little obovate, the arched back obtusely carinate, (acute 

 when dry,) the sides at length convex and sloping to the acntish 

 face which is apiculate with the short style. Exocarp thick, 

 thickened above. Putamen very thick, woody. Seed uncinate, 

 or somewhat ' curviusculo-uncinate/ (Cham.) The exocarp being 

 removed, the nutlets appear obscurely tricarinate from a sunken 

 line on each side of the acutely-carinate back, and the sides are 

 slightly impressed in the middle. As compared with the fruit of 

 P. natans that of P. amplifolius is lunate, and the exocarp being 

 removed still mucronate with the style, the sides are conspicu- 

 ously impressed at the middle, and the back is rounded-carinate. 



Potamogeton fluitans, (Roth): caule simplici tereti ; foliis 

 omuibus in petiolum attenuatis, submersis membranaceis plus 

 minus petiolisque elongatis, multinervibus ; natantibus coriaceis 

 late lanceolatis ovalibusve, petiolis rotundatis lamina plerumque 

 hand longioribus ; stipulis elongato-linguiformibus bicarinatis acu- 

 tis ; pedunculis incrassatis; spicis cylindraceis densifloris. Roth. 

 Germ, e Nolt. ! Novit Holsat.,p. 16. Chamiss. I c.,p. 219-221. 

 Fr. Novit., p. 29. Koch. Syn.,p. 673. P. natans, p. Chamiss. 

 Ada., p. 4, Sr Auct. pi. A. Gr. Man. Bot } p. 455. 



Hab. Erie Canal near Seneca Lake, and in stagnant brooks 

 emptying into the same lake, New York. Stem simple, terete. 

 Leaves all attenuate into the roundish (above scarcely flattened) 

 foot stalks, and acute both ways ; the submersed ones lanceolate, 

 more or less elongated, membranaceous, many-nerved closely 

 netted-veined, on rather elongated footstalks; the floating ones 

 coriaceous, broad-lanceolate or oval, acute, many-nerved and 

 about 6 nerves prominent beneath, very closely netted-veined, 

 from about 24 to 4£ inches long, by J to H in. wide, on foot- 

 stalks mostly shorter and never longer than the blade. Stipules 

 much elongated, strongly 2-ribbed, acute. Peduncles thickened, 

 shorter than the leaves. 'Nutlets compressed, acutely carinate.^ 

 My specimens are without fruit, but agree in every other respect 

 with those of Prof. Nolte, from Holstein, which are cited by 

 Chamisso, Fries, and Koch. The species is considered distinct 

 by these authors, and without regarding the fruit, the American 



plants appear to differ from P. natans equally with the European 

 in the attenuate base of their leaves, in the submersed leaves 

 being always present, in their more rounded petioles, and their 

 bicarinate stipules. 



