Potamogeton foliosus

Rafinesque

Medical Repository hexade 2, 5:354. 1808

Treatment appears in FNA Volume 22.
Rhizomes absent. Cauline stems slightly compressed, without spots, 4–75 cm; glands rarely present, black to gold, to 0.5 mm diam. Turions uncommon, lateral or terminal, 0.9–2.5 cm × 0.6–2 mm, soft; outer leaves 1–3 per side, base not corrugate, apex acute to apiculate; inner leaves rolled into hardened fusiform structure. Leaves submersed, ± spirally arranged, sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, greenish to brown or rarely white, not ligulate, 0.2–2.2 cm, delicate to fibrous, rarely shredding at tip, apex obtuse; blade pale green to olive-green, rarely somewhat reddish, linear, not arcuate, 1.3–8.2 cm × 0.3–2.3 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, rarely with bristle, lacunae rarely present, 0–2 rows each side of midrib; veins 1–3(–5). Inflorescences unbranched, emersed; peduncles not dimorphic, in axils of proximal, rarely distal leaves, recurved, clavate, 0.3–1.1(–3.7) cm; spikes not dimorphic, capitate to cylindric, 1.5–7 mm. Fruits pale green to olive-green or brown, obovate to nearly orbicular, turgid to concave, sessile, abaxially keeled, not laterally keeled, 1.4–2.7 × 1.1–2.2 mm, abaxial keel undulate, winglike; beak erect, 0.2–0.6 mm; sides without basal tubercles; embryo with 1 full spiral.

Distribution

V22 452-distribution-map.jpg

North America, Central America.

Discussion

Subspecies 2 (2 in the flora).

Selected References

None.

Key

1 Spike rarely interrupted; fruits olive to green-brown, 1.5–2.7 × 1.2–2.2 mm; keel 0.2 mm or more high; beak 0.2–0.6 mm; stipular veins decaying with age. Potamogeton foliosus subsp. foliosus
1 Spike interrupted; fruits pale green, 1.4–1.7 × 1.1–1.2 mm; keel less than 0.2 mm high; beak 0.2 or less; stipular veins with age remaining as fibers Potamogeton foliosus subsp. fibrillosus