Rhizomes absent; cauline stems compressed, without dark spots, 4–75 cm long. Turions uncommon, terminal or axillary, 0.9–2.5 cm long, 0.6–2 mm wide; outer leaves 1–3 per side, the base without corrugations, apex acute to apiculate; inner leaves differentiated, rolled into hardened structure, parallel to outer leaves. Nodal glands rarely present. Leaves submersed, alternate, more or less spiraling. Submersed leaves sessile; ligules inconspicuous, free from blade, light green to light brown or rarely white, fibrous or not fibrous, rarely shredding apically, persistent, convolute, 0.2–2.2 cm long, the apex obtuse; leaf blade lax, light green to dark green, linear, not arcuate, 1.3–8.2 cm long, 0.3–2.3 mm wide, with 1–3(–5) veins, 0–2 rows of lacunae each side of midrib, the base parallel-sided, not clasping, without basal lobes, the margins entire, the apex acute to apiculate, rarely bristle–tipped, not cucullate. Inflorescences unbranched, distal only; distal peduncles cylindrical, turgid, axillary, usually recurved, 0.3–1.1(–3.7) cm long; spikes emersed to submersed, capitate to rarely cylindrical, 1.5–7 mm long, the nodes 1–2, the internodes 0.6–2 mm long. Flowers whorled; perianth spathulate, clawed, the claw 0.2–0.5 mm long, the blade 0.4–1.4 mm long, 1.2–2.2 mm wide; anthers 0.3–0.5 mm long; carpels 4. Fruiting gynophore absent. Fruits circular to obovate, pale green to gray green or brown, compressed to turgid, abaxially angled, laterally rounded, 1.4–2.7 mm long, 1.1–2.2 mm wide; abaxial angles winged; beak erect, 0.2–0.6 mm long; tubercules absent; embryo ca. one full spiral.

Subspecies 2 ( in flora); North and Central America.

5a. Potamogeton foliosus C. S. Rafinesque spp. foliosus · Leafy pondweed

Potamogton foliosus C. S. Rafinesque var. macellus M. L. Fernald; Potamogeton curtissii T. Morong

Stems: glands mostly absent rarely present, when present £ 0.3 mm diam. Leaves: stipules greenish to brown, delicate to slightly fibrous, veins decaying with age. Inflorescences: spikes mostly continuous.

Fruits olive to green-brown, 1.5--2.7 ´ 1.2--2.2 mm; keel mostly ³ 0.2 mm; beak 0.2--0.6 mm 2n = 28 [K. Stern 1961]

Flowering and fruiting spring--autumn. Wide variety of waters of lakes and streams, either slow or rapidly flowing; 10--2300 m; Alta., B.C., Man., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; West Indies, Guatemala; Costa Rica.

This is probably the most common linear-leaved species in North America, as is probably the easiest to determine. Any linear-leaved specimen with fruits having an undulating wing-like abaxial keel most likely is this taxon.