Shrubs and trees; leaves alternate, simple, stipuled; blades pinnalelyveined; monoecious; flowers monosporangiate; perianth absent or calyx present; staminate flowers in drooping aments,! (apparently) to 3 in axil of each ament-bract, stamens (except in Alnus) bifid. each part bearing 1 anther-locule; carpellate flowers epigynous or perianth none, in aments or in small budlike clusters, 2-3 flowers in axil of each ament-bract; 1 or more small bracts at base of each flower; carpel 2, united, stigmas 2, ovary 2-loculed below, l-loculed above, ovules 4; seeds 1.