Description from Flora of China
Trees or rarely shrubs, deciduous, monoecious. Branchlets with chambered pith. Terminal buds with false-valved scales. Leaves odd-pinnate; leaflets 5-31, margin serrate or rarely entire. Inflorescences lateral or terminal on old or new growth; male spike separate from female spike, solitary, lateral on old growth, pendulous; female spike terminal on new growth, erect. Flowers anemophilous. Male flowers with an entire bract; bracteoles 2; sepals 4; stamens usually numerous, 6-40, anthers glabrous or occasionally with a few bristly hairs. Female flowers with an entire bract adnate to ovary, free at apex; bracteoles 2, adnate to ovary, free at apex; sepals 4, adnate to ovary, free at apex; style elongate with recurved branches; stigmas carinal, 2-lobed, plumose. Fruiting spike erect or pendulous. Fruit a drupelike nut with a thick, irregularly dehiscent or indehiscent husk covering a wrinkled or rough shell 2-4-chambered at base. Germination hypogeal.
About 20 species: mainly temperate and subtropical areas of N hemisphere, extending into South America; three species in China.