Distribution: British Columbia south on both sides of the Cascades to California, east to the Atlantic.
Habitat: Shallow ponds and streams.
Flowers: July - August
Conservation Status: Not of concern
Aquatic, herbaceous perennials from slender rhizomes, the stems very slender, freely branched, up to 10 dm. long.
Leaves alternate, submersed, narrowly linear, up to 7 cm. long and 0.5-2 mm. broad, 3-nerved, acute, bordered at the base with small, globose glands; stipules 6-15 mm. long, surrounding the stem for half their length.
Flowers perfect, in spikes 3-15 cm. long but with only 1-3 whorls, on very slender peduncles 1.5-4 cm. long; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Achenes obliquely obovoid, about 2 mm. long, not keeled, the stylar beak 0.5 mm. long, slightly recurved.