Stems submersed, elongate, branched; lvs submersed, ternately or binately dissected into filiform segments, relatively firm, not collapsing when withdrawn from water, 1-2 cm, the free petiole none or much shorter than the expanded, pubescent stipular part; fls at the water-surface, white, 1-1.5 cm wide; stamens 10-20; achenes (7-)15-25, with a straight, slender beak 0.7-1.5 mm. Ponds and slow streams; sw. Que. to Del., Tenn., and Ala., w. to Sask., Ida., Nev. and Tex. May-July.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.