Aquatic and Wetland Vascular Plants of the Northern Great Plains
55. Potamogetonaceae, the Pondweed Family
1. Potamogeton L. -- Pondweed16. Potamogeton richardsonii (Benn.) Rydb. -- Claspingleaf pondweed
Stems brownish to yellowish-green, terete, 1-2.5 mm thick, sparingly to freely branched, mostly 3-10 dm long, the shorter internodes rarely zigzag. Leaves all submersed, ovate-lanceolate to lanceolate, 2-10 cm long, 1-2.5 cm wide, with 13-25 prominent nerves, rounded to acute and not cucullate at the tip, the margin entire and undulate-crisped, sessile and strongly cordate-clasping at the base; stipules free, 1-2 cm long, early shredding into whitish fibers. Spikes dense, cylindric, 1.5-4 cm long; peduncles strongly recurved in fruit, often thickening upward, 2-10 cm long. Fruits green to brown, obliquely obovoid, 2.5-3.5 mm long, rounded to faintly keeled dorsally. Jun--Aug. Shallow to moderately deep water of fresh to brackish lakes, ponds, marshes, reservoirs and slow-moving streams; common from the n part, s to n NE; (Labr. to AK, s to PA, IN, IA, NE, CO, UT and CA). P. perfoliatus L., misapplied.
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