Herbs with basal or alternate leaves, or climbers with opposite leaves; stipules absent. Flowers bisexual or unisexual, regular, solitary or in racemes or panicles. Sepals 4–5, imbricate or valvate. Petals mostly 5 or absent. Stamens usually numerous, hypogynous. Carpels free, superior. Fruit an achene. 70 gen., mostly temp. to cold.