Stems floating or creeping; lvs orbicular, peltate, to 7 cm, crenate or shallowly lobed; peduncles usually longer than the lvs; umbels usually simple, the fls rarely less than 10, the pedicels spreading or reflexed, variable, to 1 cm; fr 2-3 mm wide, distinctly notched or cordate at base, the margins acute. N.S. to Minn., s. to Fla. and Tex., Pacific coast and trop. Amer. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.