Distribution: Alaska south on both sides of the Cascades to California, east to Newfoundland and northeastern United States.
Habitat: Shallow to deep water.
Flowers: June - July
Conservation Status: Not of concern
Aquatic, perennial herbs from slender rhizomes, the stems somewht flattened, simple or sparingly branched, 5-15 dm. long.
Submersed leaves linear, sessile, 10-20 cm. long and 3-10 mm. broad, the mid-vein bordered by rows of air chambers; floating leaves with flattened petioles shorter than the blade, the blades firm, elliptic to oblong-elliptic, 4-8 cm. long and 10-20 mm. broad, 15- to 25-nerved; stipules free, 1-3 cm. long, blunt.
Flowers in dense spikes 2-4 cm. long, on peduncles 3-8 cm. long; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Achenes obliquely and broadly obovate, 3-4 mm. long, sharply keeled on the back.