Plant: perennial, fleshy, floating or creeping, glabrous; stem often ± scapose, ribbed, hollow Leaves: simple; petiole 5-35 cm, stout; blade generally 2-5 cm wide, round-reniform, often wider than long, deeply 3-7-lobed, entire to minutely crenate INFLORESCENCE: umbels simple, dense, 5-10-flowered; peduncles 1-5 cm; pedicels short; bracts 0 or inconspicuous Flowers: many, small; calyx lobes 0 or minute; petals obtuse or acute, greenish or yellowish white to purplish, tip not incurved; stamens 5; pistil 1, ovary inferior, 2-chambered, generally with a ± conic, persistent projection or platform on top subtending 2 free stylesFruit 2 dry, 1-seeded halves that separate from each other but generally remain attached for some time to a central axis, 1-3 mm,, elliptic to round, very compressed side-to-side; ribs obscure; oil tubes 0 (but individual oil cells in fruit wall); fruit central axis not an obvious structure; Seed: face flat to convex Fruit: 2 dry, 1-seeded halves that separate from each other but generally remain attached for some time to a central axis, 1-3 mm,, elliptic to round, very compressed side-to-side; ribs obscure; oil tubes 0 (but individual oil cells in fruit wall); fruit central axis not an obvious structure; Seed: face flat to convex Misc: Lake margins, pools, etc.; 10-1500 m.