Distribution: Both sides of the Cascades in Washington; common throughout North America; Eurasia
Habitat: Shallow, fresh to brackish water.
Conservation Status: Not of concern
Aquatic, herbaceous perennials from slender rhizomes, the stems filiform, up to 4 dm. long, terete, branching dichotomously for most of their length.
Leaves alternate, submersed, filiform, mostly under 1 mm. broad, up to 12 cm. long, 1-nerved, sharp-pointed; ligules fused to the base of the leaf and forming a sheath 2-3 mm. long, longer than the free upper portion.
Flowers perfect, in spikes 1-3 cm. long in 2-5 unevenly spaced whorls, on a very slender peduncle up to 10 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, 3-3.5 mm. long, with a rounded, dorsal keel and a short, slightly curved beak.