Distribution: General in North America except Mexico and south and southeast United States.
Habitat: Sloughs and slow-moving fresh water.
Flowers: June - August
Conservation Status: Not of concern
Small aquatic herbs, the stems 5-20 cm. long, submerged or partially floating; leaf bases joined by small, winged ridges.
Submerged leaves linear, 5-20 mm. long, thin, 1-nerved, with a slight notch at the tip; floating and emergent leaves broadly spatulate, up to 4 mm. broad, 3-nerved.
Flowers imperfect, sessile in the leaf axils, each consisting of a single pistil or 1 stamen or both; styles 2, distinct, 1-2.5 mm. long, deciduous; floral bracts present.
Carpels 2, oblong-obovate, about 1 mm. long and 0.7 mm. broad, with pit-like markings in vertical lines.