Submersed lvs ternately decompound with linear segments 1-2 mm wide; emersed lvs (when present) broadly reniform, 3-parted, the segments 3-cleft, the division in turn 3-lobed; fls on long, stout peduncles; sep 4-8 mm; pet 6-14 mm; achenes plump, 1.3-2.5 mm, the sides rugose, the margin corky-thickened around the base and the ventral side below the middle; beak 0.7-1.5 mm; 2n=32. Quiet water and muddy shores, seldom wholly emersed; Me. to B.C., s. to Va., Ky., Ind., Ill., and La. Apr.-June. (R. delphinifolius)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.