Distribution: East of the Cascades in Washington; British Columbia south to California, east to the Mississippi River.
Habitat: Wet areas, often in water, in valleys and plains.
Conservation Status: Not of concern
Generally freely-branched, soft, fibrous-rooted perennial, 2-8 dm. tall, often stoloniferous from the base.
Submerged, filiform-dissected leaves often present; the lower aerial leaves with 7-21 lance-ovate leaflets with rounded teeth, up to 5 cm. long and 3 cm. wide; the upper aerial leaves with smaller and narrower leaflets with sharper teeth or even pinnatifid.
Inflorescence of several compound umbels, the 6-15 rays 1-2 cm. long; involucre and involucel of evident, narrow bracts; calyx teeth minute; petals 5, white.
Style short, stylopodium conic; fruit elliptic, glabrous, 1.5-2 mm. long, the ribs inconspicuous.