Distribution: Occurring in scattered locations in Washington; British Columbia south to California, east across Canada to New Brunswick, east in the U.S. to Idaho, Wyoming, and Utah; occurring in Mexico and South America.
Habitat: Ponds and slow-moving streams.
Conservation Status: Not of concern
Perennial, aquatic herbs, the stems simple or branched, 2-10 dm. long.
Leaves 1-2.5 cm. long, in whorls of 4-5, dissected into 13-21 filiform segments, appearing comb-like, gradually transitional to the bracts; bracts ovate-oblong, 7-10 mm. long, the lower comb-like, transitional to serrulate in the upper bracts.
Inflorescence simple to forked, submerged to emergent; flowers single, subtended by whitish, rough-edged bracteoles 1-2 mm. long; sepals 4, attached to the top of the inferior ovary, whitish, serrate; petals 4, about 2.5 mm. long, quickly deciduous; stamens 8 on the staminate flowers; stigmas plumose on the pistillate flowers.
Achene smooth, 2 mm. long.