Distribution: North and South America and Greenland.
Habitat: Sloughs and slow-moving, fresh water.
Flowers: April - July
Conservation Status: Not of concern
Small aquatic herbs, the stems 0.5-4 dm. long, emersed to emergent, with small, membranous ridges between the leaf bases.
Emersed leaves linear, 1-nerved, 0.5-2.5 mm. long; floating and emergent leaves broadly obovate, 3-nerved, up to 1 cm. wide.
Flowers imperfect, sessile in the leaf axils, each consisting of a single pistil or 1 stamen or both; styles 2, distinct, 1-5 mm. long, persistent; floral bracts present.
Carpels 2, obovate, 0.7-1.2 mm. long and broad, wingless, pitted with small, shallow pits.