Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across much of North America to the Atlantic Coast; also in Eurasia.
Habitat: In standing or slow-moving fresh water.
Conservation Status: Not of concern
Floating aquatic perennials forming colonies, lanceolate-ovate body 1-4 mm long, flat and barely gibbous, margins entire, often reddish below with coloring beginning where root is attached, sometimes red-spotted on upper surface; turions sometimes present; stipes small, white, usually decaying; roots less than 15 cm, tip generally rounded, sheath not winged.
Plants rarely found in flower, reproducing vegetatively; flowers 1-2 per body, surrounded by utricular scale with narrow opening at apex; stamens 2, 4-chambered, ovaries 1, containing 1 ovule, tapering into style, stigma funnel-shaped.
Fruit a follicle, 0.5-0.6 mm, not winged, opening by bursting; seeds 1-5, with 30-60 indistinct ribs.