Perennial herbs, often arising from thick, branching rhizomes. Lvs alternate, mostly in basal rosettes, imparipinnate; leaflets serrate; stipules persistent, adnate to petiole for lower ⅔. Fls in dense terminal clusters or spikes, subtended by several bracteoles, ☿ or unisexual, 4-merous, small, sessile. Hypanthium deeply concave. Epicalyx 0. Sepals greenish or purplish. Petals 0. Stamens 4-numerous. Ovary superior, surrounded by the hypanthium; carpels 1-2-(3); styles terminal and filiform; ovules solitary. Fr. of 1-(several) achenes enclosed in hardened, dry, 4-angled, sometimes ± flattened or cup-like hypanthium with variously sculptured faces and sometimes thickened or winged angles.