28 
Stipules 2-3 inches long, obtuse, strongly bicarinate. Peduncles 
usually thicker than the stem, sometimes thickening upwards, 2-4 
inches in length. Spikes 1-2 inches long, fruiting freely. . Fruit 
roundish or obovate, 112-2 lines long and 1-1% lines broad, dor- 
sally 3-keeled, the middle keel sharp; straight or curved on the 
face; style facial, short, bluntish; apex of the embryo pointing 
transversely inwards. 
This species is evidently allied to Zucezs in habit, and with that 
species, P. angustifolius, P. spathuleformis and P. heterophyllus, 
forms a very natural group, but it is clearly distinct from all of 
them in its vigorous growth, its abundant foliage, its ample float- 
ing and submerged leaves, and its large, strongly 3-keeled fruit. 
In two or three recent publications some doubts have been 
thrown upon the specific status of this plant, which, considering 
its marked individuality, are, to say the least, rather surprising. 
Mr. Hill, in Bull. Chicago Ac. for 1891, p. 125, says: «* 
a doubtful species at best.” It seems to me not half so doubtful 
as many other species of good standing that might be mentioned. 
In fact, its peculiarities are strikingly manifest. 
In A. Gray, Man. Ed. 6, it is said to be * very near amplifolius,” 
a species with which it has very few characters in common. The 
eminent Scandinavian Potamogetonist, Dr. Tiselius, whose au- 
thority upon Northern European species no one will question, 
identifies it with P. Jonchites (sub. nom. Р. fluitans, Roth.*), but it 
certainly bears little resemblance to any form of that species grow- 
ing in this country. Nor does it square with any of the examples 
of this species sent to me from Sweden by my distinguished 
friend. In his article he compares the floating leaves of my species 
with those of autumnal shoots of P. fluitans, апа, finding them. 
similar, rather hastily, I think, pronounces them specifically identi- 
cal, but he overlooks the fact that non-fruiting autumnal growths 
are nearly always abnormal. Were there no other differences, the 
entire dissimilarity between these two species in the stipules, sub- 
merged foliage and fruit are quite sufficient to separate them 
widely. 
Our plant was first discovered by Mr. H. N. Patterson in the 
* See Nordstedt’s Botaniska Notiser for 1887, p. 253. 
