Trees with thin exfoliating bark. Leaves alternate, deciduous, palmately lobed. Stipule thin, sheathing, entire or toothed. Petioles dilated at base and largely covering the buds. Inflorescence of spherical unisexual heads, in our species these racemose on long slender peduncles. Calyx minute, of 3-8 scale-like sepals; petals minute, 3-6, those of pistillate flowers rounded. The family is comprised of a single ancient genus, with a number of fossil species extending back to the Cretaceous. Its relationship to other families is little understood. Abrams, Vol. II 406. Nine species of the north temperate regions.