Sp. Pl. 1: 558. 175.
Gen. Pl. ed. 5, 244. 1754.
Herbs, perennial, from thick caudices 0.5-2 cm or slender stolons. Leaves basal and cauline, simple; proximal leaves petiolate, distal leaves sessile or nearly so; cauline leaves alternate. Leaf blade unlobed, oblong-ovate to orbiculate-reniform or cordate, margins entire, dentate, or crenate. Inflorescences terminal or axillary, 1-6-flowered cymes or flowers solitary, to 22 cm; bracts leaflike, not forming involucre. Flowers bisexual, radially symmetric; sepals not persistent in fruit, 5-12, white, pinkish, yellow, or orange, plane, oval-orbiculate to narrowly obovate, 4-23 mm; petals absent; stamens 10-40; filaments filiform; staminodes absent between stamens and pistils; pistils 5-55, simple; ovules 15-35 per pistil; style 0.1-2 mm. Fruits follicles, aggregate, sessile or stipitate, linear-oblong to ellipsoid, sides prominently veined or not; beak terminal, straight or weakly curved, 0.2-2 mm. Seeds brown, elliptic to broadly elliptic, rugulose. x=8.
Primarily temperate wetlands, worldwide.
Species 10 (3 in the flora).
|1||Stems leafless, or with 1 leaf; sepals white to yellow, not orange or pinkish.||Caltha leptosepala|
|1||Stems leafy; sepals white, yellow, or orange, or pinkish.||> 2|
|2||Stems creeping or floating, rooting at nodes; sepals white or pinkish, 4–7(–8) mm; follicles 20–55, bodies 3.2–6.5 mm; seeds 0.5–0.8 mm.||Caltha natans|
|2||Stems erect, or sprawling with age and then producing shoots and roots at nodes; sepals yellow or orange, (6–)10–25 mm; follicles 5–15(–25), bodies 8–15 mm; seeds 1.5–2.5 mm.||Caltha palustris|