

On American Species of the Genus Potamogeton. 351 



Torr. /) I gathered in the Niagara rapids, near Bath island, and 

 have since received from Penn Yan, New York, (Dr. Sartwell,) 

 a remarkable state of this species probably to be referred to the 

 amphibious form of Fries. In this the stem is simple (compare 

 Fries's observations, Novit., p. 39, on an analogous state of P. 

 gramineus c primo obtutu cum P. oblongo conjungenda'), and the 

 broad, oblong, or oval leaves are either all coriaceous and floating, 

 or only the lowest submembranaceous : the length of the flatten- 

 ed petioles being often almost the only index to the real affinity 

 ot the plant, the whole habit of which accords, often strikingly, 

 with that of P.fluitans ; but its strongly marked fruit at once 

 refers it to the present species. The published description of the 

 fruit of this species was from- immature nutlets. The following 

 is taken from perfectly ripe ones observed in the Niagara plants, 

 in those of the Connecticut above mentioned, and (in the dry 

 state) in the admirable specimens of Dr. Sartwell. Fr. recentes 

 oblique obovati lunati, compressiusculi, subtricarmati, stylo apicali 

 apiculati, dorso arcuato acute praecipue superne snbalato-carinato 

 sinuato-dentati, carinis lateralibus subobsoletis, facie recta obtnsa. 

 The lateral keels are conspicuous when dry. Exocarp thin. 

 Putamen thick, and thickened above. Seed uncinate, a little 

 curved. The exocarp being removed, the back appears acutely 

 carinate, and a little alate, especially above; with a sunken line 

 one each side defining the rather obscure, obtuse, lateral keels ; 

 the sides a little impressed at the middle. At the conclusion of 

 the Monography of Chamisso a large number of Potawogetons, 

 exotic as respects Europe, of which the specimens were insuffi- 

 cient to permit of their satisfactory determination, are thrown 

 together as provisional varieties of P.fluitans; — the learned au- 

 thor, leaving it, as he says, to others, to distinguish and designate 

 these plants, so far as might turn out to be necessary, as species. 

 Two of these (pp. 226, 227) have been already referred, in the 

 previous number of this Journal, already cited, to P. Claytonii ; 

 and the only remaining North American Potamogeton noticed, 

 {P.fluitans, e. American^ Americanus, thus provisionally desig- 

 nated, p. 226,) is most probably an amphibious state, like one 

 above described from Niagara, of P. lonchites ; and if so, as the 

 species just named is typically, judging from its most perfect con- 

 ditions, a branched Potamogeton, of a distinct tribe from P.flui- 

 tans, there can be no doubt of the necessity of separating Cha- 

 misso's plant from the latter. It is however so near to the P. 

 nodosus of Poiret, Enc. Suppl. iv, p. 535 (the P.fluitans, c. ra- 

 naricnses, nodosus, Chamiss. L c , p. 222), as the German author 

 himself remarks, that I cannot but consider it possible that the 

 several American plants, brought together, in these papers, under 

 the name of P. lonchites, together with Chamisso's specimens 

 above quoted, may finally prove to be identical with the older 





