Stems glabrous. Leaves all laminate, filiform-dissected leaves absent. Leaf blade reniform, 0.4-1 × 0.6-1.7 cm, margins shallowly crenate-lobulate, segments rounded. Flowers: receptacle glabrous; sepals recurved, 1.5-2 × 1-1.5 mm, glabrous; petals 5, 2-4 × 1-1.5 mm; style 0.1 mm. Fruiting pedicels recurved. Heads of achenes globose or depressed-globose, 3-4 × 3-4 mm; achenes 1.2-1.6 × 1-1.2 mm, glabrous; beak deciduous, sometimes leaving stub to 0.1 mm. 2 n = 16 (Europe).

Flowering spring-summer (Apr-Aug). Edges of lakes and ponds on the coastal plain; 0-150 m; Nfld.; Md., N.C., Pa., S.C., Va.; Europe.

Stems creeping; submersed lvs none; floating lvs long- petioled, shallowly 3-5-lobed; fls white, 5-7 mm wide; receptacle glabrous; 2n=16. Shallow water and wet shores; coastal plain from se. Pa. to S.C.; also Nf. and Europe. May-Aug.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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