Perennial herbs. Stipules adnate to petiole and ± sheathing the stem. Leaves circular or reniform in outline, palmately lobed. Inflorescences axillary. Flowers small, bisexual, green or yellowish, usually 4-merous. Hypanthium urceolate, persistent, bearing around the constricted mouth 2 series of 4 elements: the outer ("epicalyx lobes") alternating with the inner ("calyx lobes"). Petals 0. Stamens usually 4. Achenes 1-8(-12), included within an inflated, membranous urceolate calyx.