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Umbels simple, bracts 0 or minute. Fls. 5-merous; calyx-teeth us. obsolete; stamens inflexed in bud; styles filiform. Fr. laterally much-compressed, commissure very narrow, carpophore 0. Vittae 0 or sunk in primary rib or replaced by ± continuous oil-bearing layer. Mericarps with us. 1 (often obscure) rib on face. Seed invested by woody covering. Small perennial herbs. A widespread genus of some 75 spp., sts treated as constituting a separate family-Hydrocotylaceae. The N.Z. spp. are perennial herbs, often forming large patches; stems ± slender, branching, creeping, rooting at nodes; lvs us. clustered at nodes, simple to 3-5-foliolate, of ± orbicular-reniform order; stipules scalelike.
Fr orbicular to ellipsoid, strongly flattened laterally, its ribs evident to obsolete, the secondary ones not developed; each mericarp with a layer of sclerenchyma surrounding the seed-cavity; carpophore wanting; peduncles axillary, elongate to nearly obsolete, bearing a simple umbel, or the umbel proliferous into an interrupted (sometimes forked) spike; invol small or none; sep minute or obsolete; pet white in our spp.; small perennials, the slender stem prostrate or arched and rooting at the nodes, with simple, long-petiolate, broadly ovate to orbicular or reniform, sometimes peltate lvs. 75, mostly warm reg.
Perennial, stems prostrate or rooting at the nodes, sometimes suberect. Leaves petiolate and stipulate, in outline rhomboid, peltate or cordate, palminerved, entire, lobed or divided, crenate to crenate-serrate. Umbels simple, sometimes irregularly subcompound. Involucral bracts few or 0. Calyx teeth minute or obsolete. Petals entire, valvate in bud. Disk plane, margin elevated. Styles from the base filiformous or with thickened base. Fruit laterally flattened, commissure narrow; vittae 0; mericarps with dorsal ribs, marginate, lateral ribs in the commissure, intermediate ones straight or arcuate.
Glabrous or hairy, annual or perennial herbs, creeping and rooting at nodes. Lvs simple, ± entire to serrate, crenate, or palmately lobed or palmately 3-5-foliolate, petiolate, stipulate. Umbels simple or with successive whorls of fls; bracteoles small or 0. Petals white or green, tinged yellow or pink, with apex entire, acute, and not inflexed; calyx teeth small or 0. Fr. strongly laterally flattened and narrowed to commissure; mericarps orbicular or ovate; dorsal ribs acute, furrowed or obsolete; lateral ribs slender, acute, furrowed, or rarely obsolete; vittae in primary ribs or 0.
