POLTSONACEOUS GENERA. 27 



em plant for which so unhappy a misnomer as " P. amphibium, 

 Linn." has hitherto prevailed. The plant of northern and mid- 

 dle western Europe has not only a lanceolate and subcordate 

 foliage, hut the margins of its leaves are keenly scabrous-serru- 

 late. No such plant, or any presenting even a hint of these two 

 excellent characters, has been found by me in the herbaria that 

 I have consulted. It does not exist in North America. Muh- 

 lenberg and Willdenow a hundred years age made this out, and 

 published either this or some other species as P. coccineum. Pre- 

 cisely what that was, however, as to the aquatic type, one can 

 not now say. But Amos Eaton as early as 1840 gave the name 

 P. fluitans to what, from the description as well as the locality, 

 we must conclude to have been that here described anew. I do 

 not know where that St. John's Lake is which Michaux cites as 

 the habitat of his var. natans ; but I suspect it to be some north- 

 ern lake now known by another name, and lying within the hab- 

 itat of P. fluitans, in which case that may be an older, though a 

 merely varietal designation which would in my view be of no 

 consequence. 



It will devolve upon botanists resident in various parts of the 

 extensive area occupied by P. fluitans to find, if it may be found, 

 the riparian state. Unless it be a deep-water plant always, on 

 some muddy shores will be found the emersed and creeping form ; 

 and it may be predicted that the leaves of such will have a lan- 

 ceolate outline. 



P. PUKPUBATA. Aquatic. Habit of P. fluitans, quite as 

 slender, the internodes as long, but floating portion of stem with 

 distinctly swollen nodes, and very short ocrese : slender petioles 

 1 to IJ inches long, oblong-elliptic blades 11 to 4 inches, thin, 

 purple tinged, always acute at both ends, most so at apex : spike 

 solitary, small-flowered, very dense, ovate, the pedicels spreading : 

 achenes small, round-ovate, acute, dull blackish, neither quite 

 smooth nor with a definable unevenness. 



Kiparian state. Stems mainly prostrate, rooting in mud, stout 

 and fistulous, the internodes 3 or 4 inches long and cylindric : 

 leaves lanceolate, very acute, 4 or 5 inches long beyond the short 

 petioles, glabrous on both faces, only the reduced uppermost 

 and floral muriculate-scabrons on midvein and margin : spikes 



