354 On American Species of the Genus Potamogeton. 



monly not twice as long as the cylindrical, rather few-flowered 

 spike. Nutlets large, oblong, a little rostrate with the apical, slight- 

 ly recurved style; the broad back acutely carinate, and sinuate- 

 dentate, with one prominent tooth near the base; the lateral keels 

 obsolete, sides rather convex, and impressed at the middle, (but not 

 so, according to Chamisso, in the entirely mature fruit ;) the face 

 obtusely carinate. Exocarp thick. Putamen thickish, not hard. 

 See.l uncinate-convolute. Chamisso does not describe the fruit 

 of 1 J . compressus as minutely, in some respects, as in other species, 

 and his figure corresponds less nearly with the nutlets of our 

 plants, thau the general features of his description. The denta- 

 tion of the back is not mentioned in any description that I have 

 seen of the present species, and if, as appears to me nearly cer- 

 tain, the American plants above described are inseparable, specifi- 

 cally, from the European, this character, a conspicuous one in 

 several American species, must be reckoned of secondary im- 

 portance. 



PoxAMOfiETON Niagarensis, (Sp. nov.): caule complanato an- 

 cipi-ti rigidiusculo ramoso ; foliis omnibus submersis rnembrana- 

 ceis firmioribus linearibus versus apicem sensim attenuatis apice 

 acutis mucronulatis, basi attenuatis subpetiolatis, sub-trinervibus; 

 stipulis lato-linearibus membranaceis acutiusculis demum laceris; 

 pedunculis compressisclavatis brevissimis; spicis paucifloris capi- 

 tals; fructibtis recentibus lenticulari-compressis oblique subro- 

 tundo-obovatis stylo apieali mueronatis, dorso deorsum curvato 

 acute lato-alato-carinato, carina superne subgibboso-producta, sin- 

 uato-dentata, lateribus convexiusculis in faciem subalato-carina- 

 tam deckvibus. 



Hab. Niagara falls, near the brink of the Hog back, growing 

 plentifully with Udora ; and elsewhere in the river. Fr. Au- 

 gust — September. Stem much compressed and sharply two-an- 

 gled, firm, much branched, 1-2 feet long. Leaves all submersed, 

 membranaceous, rather firm, dark green, linear, above sensibly ta- 

 pering to the suddenly acute and mucronulate tip ; at the base 

 much attenuate, subpetiolate ; 3-5-nerved, the exterior lateral 

 nerves commonly obscure or obsolete; the space next the midrib 

 on each side more or less evidently reticulate-cellulose ; very ob- 

 soletely and sparsely veined ; ]£-3£ inches long by half a line 

 to rather more than a line wide. Stipules broad-linear, mem- 

 branaceous, finely nerved, acutish at the tip, which is at length 

 lacerate or even setose; the longest 6-S lines long. Peduncles 

 not numerous, axillary, erect, very short, compressed, clavate, 

 2-4 hues long. Spikes few- (8-12) flowered, capitate, subglo- 

 bose. Nutlets somewhat rounded, lentiform-compressed, the 

 back curved downward below the apparent base, broadly alate- 

 carinate, sinuate-dentate, a little hunched above, the sides convex 

 and sloping to the aiate face which is produced-acute at the 





