Potamogeton epihydrus Raf.

Potamogeton epihydrus Raf. Med. Repos. II. 5: 354. 1808
Potamogeton natans Michx. Fl. Bor. Am. 1 : 101. 1803. Not P. natans I,. 1753. Potamogeton Nutlallii Cham. & Schlecht. Linnaea 2 : 226. 1827. Potamogeton Pennsylvanicus Cham. & Schlecht. Linnaea 2 : 227. 1827. Potamogeton pumilus Wulfg.; R. & S. Syst. Veg. Mant. 3 : 354. 1827, • Potamogeton Claytoni Tuckerm. Am. Jour. Sci. 45 : 38. 1843. Potamogeton Nuttallii ramosus Peck, Ann. Rep. N. Y. State Mus. 47 : 162. 1894. Potamogeton Nuttallii cayugensis Wiegand, Rhodora 2 : 102. 1900.
Stem simple or branched ; floating leaves petioled ; blades elliptic-lanceolate, or rarely obovate, obtuse at the apex and narrowed at the acute base, 3.4-9 cm. long, 6-17 mm. wide; petioles 2.5-10 cm. long; stipules free from the petioles, obtuse, 1.8-2.7 cm. long; submerged leaves sessile, the blades linear or linear-lanceolate, 5-nerved, with a cellular reticulation along the midrib, 6-14 cm. long, 2.5-4 mm. wide ; spikes cylindric, 1.2-6 cm. long, many-flowered ; nutlets deeply pitted, 3-keeled, the middle keel sharp ; embryo a complete spiral, the curved apex pointing inside the base and upward.
Type locality : Canada. _
Distribution : Newfoundland to British Columbia, south to North Carolina and Iowa.