Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast; cosmopolitan.
Habitat: In standing or slow-moving fresh water
Flowers: June - October
Conservation Status: Not of concern
Floating aquatic perennials forming colonies, ovate body 1-8 mm long, flat and barely gibbous, margins entire, rarely slightly reddish beneath, sometimes diffusely red above; stipes small, white, usually decaying; roots 15 cm or shorter, sheath not winged.
Plants rarely found in flower, reproducing vegetatively; flowers 1-2 per body, surrounded by a utricular, membranous scale; stamens 2, 4-chambered; ovaries 1, containing 1 ovule, tapering into style, stigma funnel-shaped.
Fruit a follicle, 0.8-1 mm, laterally winged toward tip, opening by bursting; seeds 1-5, with 8-15 ribs.