



On American Species of the Genus Potamogetoin 359 



uate when dry,) the sides flatfish, and impressed at the middle ; 

 the face obtuse, one-toothed near the base ; the style facial, and 

 very short. Exocarp thick. Putamen thickish. Seed convo- 

 lute-uncinate. I have seen no specimens of the European plant, 

 but Chamisso's minute description, and his figure of the fruit, 

 leave little or no doubt of the identity of ours with it. It is ob- 

 servable that the sinuate-dentation of the back of the nutlets, 

 noticed in the American specimens of P. compressus, but not 

 mentioned as occurring in any European species by Chamisso, is 

 found also in the present. 



Potamogeton hybridus, Michx. Since the publication of my 

 notes upon this species, I have had an opportunity of examining 

 the Potamogetons in the herbarium of Prof. Torrey, and have 

 found specimens of P. hybridus from New Jersey, Virginia, 

 Georgia, Alabama and Louisiana, none of which differ, so far as 

 I have observed, materially, from the description above referred 

 to, and all of which seem to me to confirm the characters of the 

 fruit there detailed (as to its small size, its shape, and its distinct, 

 sharp, often toothed lateral keels) which were relied upon as sus- 

 taining the remarkable difference of the submersed leaves, that 

 appeared to distinguish this species from P. Spirillus, also there 

 described. Chamisso considered P. hybridus, it would seem, to 

 belong to the tribe Natantes, and he remarks that its leaves are to 

 be regarded as bladeless petioles. But this will appear less prob- 

 able on comparing it with P. Spirillus, (a plant unknown to the 

 German author,) which explains the characters of the former 

 species (somewhat obscure from its tenuity) and makes evident 

 that both are to be referred to the section Graminifolii, and 

 viewed, as perhaps, by the attachment of their leaves to the sti- 

 pules, the connecting links between the tribes Compressi and 



Pectin ati. 



Potamogeton tectinatus, (L.): caule subtereti ramosissimo ; 



foiiis omnibus submersis membanaceis cum stipulis connatis basi- 



que vaginantibus lineari-setaceis versus apicem sensim attenuatis 



acutissimis, uninervibus, venosis ; ligulis longiusculis scariosis 



demum lacero-setosis ; pedunculis filiformibus aequalibus elonga- 



tis ; spicis longiusculis interrupte verticillatis : fructibus recenti- 



bus oblique lunato-obovatis compressis, stylo facial) brevissimo 



apiculatis, dorso latiori rotundo-carinatis, carinis lateralibus obso- 



letis, lateribus planiusculis in faeiem acuta m declivibus. P. pec- 



tinatus, L. Sp. 183, e Koch. Pursk ! FL 1, p. 12 1. Torr. ! 



PL U. S.j p- 198. Chamiss. in Limma, 2, p. 164, t iv, f. 2. 



Fries Norit.,p. 52. Koch Syn. p. 677. Beck Bot., p. 386. 



Ktk Enum. 3, p. 137, (excl. P. marine.) A. Gr. ! Man. Bot., 

 1 p. 4.17, (excl. P. marine) Wood Bot., p. 526, (excl. syn.) 



P. marinus, Michx., FL I, p. 102, e descr. 



/ 









