Distribution: Occurring on both sides of the Cascades crest in Washington; widely distributed throughout much of North America.
Habitat: Ponds and slow-moving streams.
Origin: Introduced from South America
Conservation Status: Not of concern
Perennial, aquatic herbs, the stems sturdy, 2-4 mm. thick and 1-9 dm. long, completely submerged until time of flowering.
Leaves in whorls of 4-6, all finely pinnatifid, 2.5- 5 cm. long, the 25-37 divisions filiform; stipules linear.
Flowers in the axils of submerged leaves along the main stem, with minute, linear to filiformly dissected bracteoles; sepals 4, attached to the top of the inferior ovary; staminate flowers with 4 small petals and 8 stamens; pistillate flowers with no petals, the stigmas plumose.
Achene 1.5-2 mm. long.