Annual herbs, stems bristly hairy. Leaves simple but deeply palmately dissected, sessile or petiolate; stipules present, large, connate, lobed and similar in appearance to leaves. Inflorescence in dense sessile clusters (cymes) opposite leaves, surrounded by fused stipules. Epicalyx bracts 4; sepals 4 or 5 (occasionally 6) and larger than epicalyx bracts; petals absent; hypanthium urn-shaped; stamens usually 1, occasionally 2, inserted on disc; ovary superior, 1-locular with 1 ovule; stigma and style 1. Fruit an achene enclosed in hypanthium.
20 species, in the temperate Northern Hemisphere and Australia; 1 endemic, 2 naturalised in Australia.
Identification of all 3 species is difficult, with specimens displaying a high degree of variability. The genus in Australia warrants further study.