72 NAIADACEAE. 
17. Potamogeton confervoides Reichb. Alga-like Pondweed. (Fig. 158.) 
waa oes confervoides Reichb. Ic. Fl. Germ. & Helv. 7: 
Potent trichoides A. Gray, Man. 457. 1848. Not Cham. 
Potamogeton Tuckermani Robbins; A. Gray, Man. Ed. 2, 
434. 1856. 
Stems slender, terete, much branched, the upper 
branches repeatedly forking, 6’-18’ long. Leaves very 
delicate, flat, setaceous, 1’-214’ long, the broadest scarcely 
4’ wide, tapering to a long hair-like point, 1-3-nerved 
and often with a few cross-veins, bright green or yellow- 
ish ; stipules delicate, obtuse, 2’”-3’’ long; peduncles 2/-8/ 
long, erect, somewhat thickened upward ; spikes capitate, 
3’’-4’’ long; fruit roundish-obovoid, 1/’-144/’ long and 
about as thick, the back sometimes a little angular or sin- 
uate, 3-keeled, the middle keel sharp, the face notched 
near the base, the sides impressed with a shallow indenta- 
tion which runs into the notch of the face; apex of the 
embryaq nearly touching the base a little to one side. 
In cold or mountain ponds, Maine and New Hampshire to 
New Jersey and Pennsylvania. Alsoin Europe. Aug.—Sept. 
18. Potamogeton crispus I, Curled-leaved Pondweed. (Fig. 159.) 
Potamogeton crispus l,. Sp. Pl. 126. 1753. 
Stems branching, compressed. Leaves 2-ranked, 
linear-oblong or linear-oblanceolate, sessile or semi- 
amplexicaul, obtuse at the apex, serrulate, crisped, 
4/-4/ long, 3/’-7’’ wide, 3-7-nerved, the midrib 
often compound and the outer nerves very near the 
margin ; stipules small, scarious, obtuse, early per- 
ishing ; peduncles 1/—2’ long, frequently recurved 
in fruit, sometimes very numerous; spikes about 
34’ long, appearing very bristly with the long- 
beaked drupelets when in fruit; fruit ovoid, about 
14’ long, 1’’ or more wide, 3-keeled on the back, 
the middle keel with a small projecting tooth near 
the base, the face slightly curved, the style facial 
and nearly as long as the drupelet ; embryo small, 
its apex pointing directly toward its base. The 
plant is mainly propagated by peculiar winter buds, 
In fresh, brackish or even salt water, Massachusetts 
to Pennsylvania and Virginia. Alsoin Europe. Aug. 
19. Potamogeton zosteraefolius Schum. Eel-grass Pondweed. (Fig. 160.) 
Potamogeton zosteraefolius Schum. Enum. Pl. Saell. 50. 
Piped reson. compressus Fries, Novit. Ed. 2, 44. 1828. 
Not L. 1753. 
Stems much flattened, sometimes winged, widely 
branching. Leaves linear, obtuse and mucronate or 
short-pointed at the apex, 2’-12’ long, 1’’-2’” wide, with 
3 principal nerves and many fine ones; stipules scari- 
ous, obtuse, finely nerved, soon perishing ; peduncles 
1%4/-4’ long; spikes cylindric, about 44’ long, 12-15- 
flowered; fruit obovoid with a broad base, about 2// 
long, 114 ’’-14’’ thick, 3-keeled on the back, the lateral 
keels rather obscure; face arched, beaked with a 
short recurved style; embryo slightly incurved. The 
plant is propagated by the terminal leaf-buds, which 
sink to the bottom, and rest during the winter. 
In still or running water, New Brunswick to New Jer- 
sey, west to Oregon. Alsoin Europe. July-Aug. 
