Aquatic and Wetland Vascular Plants of the Northern Great Plains
55. Potamogetonaceae, the Pondweed Family
1. Potamogeton L. -- Pondweed11. Potamogeton natans L. -- Floatingleaf pondweed
Stems slightly compressed, 0.8-2 mm thick, simple or rarely branched, to 2 m long. Submersed leaves reduced to linear, bladeless phyllodes, these often disintegrating with age, 10-20 cm long, 1-2 mm wide, tapering to an obtuse tip. Floating leaves ovate-lanceolate to ovate-elliptic, 3-10 cm long, 1-5 cm wide, mostly 19- to 35-nerved, acute to obtuse at the tip, rounded to cordate at the base; petioles usually much exceeding the blade in length, usually forming an angle with the blade at their juncture; stipules free, fibrous, persistent or shredding with age, 4-10 cm long. Spikes dense, cylindric, 2-5 cm long; peduncles thicker than the stem, 3-10 cm long. Fruits greenish-brown to brown, obliquely elliptic-obovoid, 3-5 mm long, often pitted on the sides, the dorsal keel sharp or rounded with age, the lateral keels obscure. Jul--Aug. Shallow to rather deep water of lakes and ponds; frequent in the Turtle Mts., ND, and NE Sand Hills, otherwise uncommon; (Circumboreal, in N.Amer. s to PA, IN, IA, n KS, NM, AZ and CA).
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