50 
the leaf for about one-half their length. In dried specimens, the 
stipules appear free from all the floating leaves. Emersed pe- 
duncles usually similar to those of the preceding species. Sub- 
merged peduncles usually wanting, or at most, hardly 1 line long. 
Spikes above water 3-5 lines long, continuous, while the lower 
are mostly sessile in the axis of branches, capitate aud ripening 
from 1 to 4 fruit. Fruit cochleate, very thin, nearly fleshless, 
roundish, about 3% line long and nearly as broad, flat and deeply 
‚ impressed on the sides, 3-keeled on the back, middle keel winged, 
wing broad and with 4 or 5 large teeth or very narrow and with- 
out teeth, the lateral keels rounded; style usually marked on the 
dried fruit only by a slight projection or a scar; embryo commonly 
coiled about 134 turns. The spiral markings of the embryo are 
distinctly seen in the dried fruit, and are a very distinctive feature, 
strongly reminding one of a small snail shell. 
Pools, ditches and ponds. Nova Scotia (Mrs. E. С. Britton); 
New Brunswick, Quebec and Ontario (Macoun). Common in 
New England, and west to Minnesota, Missouri (Blankenship) 
and Nebraska, south to Pennsylvania and Virginia. (Plate LVI.) 
.. 33. POTAMOGETON FILIFORMIS, Pers. Syn. i. 152 (1805). 
P. marinus of authors, not L. Herb. 
Stems from a running rootstock, slender, 3-20 feet in height, 
filiform above, stout and thick towards the base. Flowers on 
long, often drooping peduncles, the longest measuring 6 to 8 
inches, 2-4 in a whorl and the whorls 4-1 inch apart. Leaves 
numerous, 2—10 inches long and from ¥ to 14 line, very rarely 14 
line, broad, 1-пегуед, with a few cross nerves. Sheaths about 1 
line long, and the free part of the stipule 1% inch more, scarious оп 
the edges. From 3 to 12 drupes are ripened in a verticil. Fruit 
1-174 lines long and about 3% line wide; sides even; back not 
keeled in fresh specimens and scarcely so in the dry; face nearly 
straight or obtusely angled near the top; stigma nearly or quite 
sessile, remaining on the dry fruit as a broad truncate projection, 
apical or subapical; embryo circle incomplete, the apex pointing 
slightly inside of the basal end. 
Var. MACOUNII, Morong, Macoun's Cat. Can. Pl. pt. 4. 88 (1888.) 
Quite a distinct form with leaves 1-3 inches long, the largest 
% a line or a little more in width, obtuse, stiff, with a strong mid- 
