Distribution: Widely distributed in much of Washington; Alaska south to California, east to the Rocky Mountain states.
Habitat: Ponds and shallow lakes at moderate elevations in the mountains.
Conservation Status: Not of concern
Dioecious, aquatic perennials from rhizomes, the stems usually floating, 3-10 dm. long.
Leaves alternate, linear, slightly rounded on the back, 2-6 mm. broad, the upper ones sheathing at the base.
Flowers in globose clusters toward the tip of the main stem; staminate heads up to 5, above the pistillate; pistillate heads 2-4, the lower 1-2 long stalked and borne in the axils of leaf-like bracts, up to 1.5 cm. thick; stamens 3-5 with 3-5 minute chaffy bracts, with long filaments; style 1, with a larger bract.
Achenes spindle-shaped, about 2.5 mm. long, on a stipe 1-1.5 mm. long, and with a beak about 2 mm. long.