About 15 genera and more than 150 species of deciduous trees and shrubs with watery juice, widely distributed in tropical and temperate regions, yielding important street and shade trees. Buds scaly; lvs. alternate, simple, serrate, pinnately veined, petioled, stipules usually fugacious; fls. bisexual or unisexual, small, clustered or the pistillate solitary, apetalous; calyx 3-9 parted; stamens as many as calyx lobes and opposite them, rarely twice as many, filaments straight; ovary superior, usually 1-celled, 1-ovuled, styles 2; fr. a samara, nut or drupe.