POLYGONACEOUS GENERA. 27 
ern 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, but 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 speciesas 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. zatans ; 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. fuitans 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 purPURATA. Aquatic. Habit of Z. fluttans, quite as 
slender, the internodes as long, but floating portion of stem with 
distinctly swollen nodes, and very short ocreæ : slender petioles 
1 to 14 inches long, oblong-elliptic blades 13 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. 
Riparian 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-scabrous on midvein and margin: spikes 
