Distribution: Occurring chiefly west of the Cascades crest and in the Columbia River Gorge in Washington; southwestern British Columbia to California, east across the U.S. in scattered locations to the Atlantic Coast.
Habitat: Floating on surface of calm water or on face of vertical rock seeps.
Conservation Status: Not of concern
Floating aquatic perennials forming colonies, lanceolate-ovate body 0.8-4 mm long, flat to somewhat thick, margins entire; stipes small, white, usually decaying; roots to 1.5 cm, tip rounded or pointed, sheath not winged.
Plants rarely found in flower, reproducing vegetatively; flowers 1-2 per body, surrounded by utricular scale open on 1 side; stamens 2, 4-chambered, ovaries 1, containing 1 ovule, tapering into style, stigma funnel-shaped.
Fruit a follicle, 0.6-1 mm, not winged, opening by bursting; seeds 1-5, with 12-15 distinct ribs.