Sp. Pl. 2: 999. 175.
Gen. Pl. ed. 5, 434. 1754.
Trees, aromatic and resinous, glabrous or with simple hairs. Bark gray-brown, deeply furrowed; liquid, and Arabic ambar, [amber] twigs and branches sometimes corky-winged. Dormant buds scaly, pointed, shiny, resinous, sessile. Leaves long-petiolate. Leaf blade fragrant when crushed, (3-)5(-7)-lobed, palmately veined, base deeply cordate to truncate, margins glandular-serrate, apex of each lobe long-acuminate. Inflorescences terminal, many-flowered heads; staminate heads in pedunculate racemes, each head a cluster of many stamens; pistillate heads pendent, long-pedunculate, the flowers ± coalesced. Flowers unisexual, staminate and pistillate on same plant, appearing with leaves; calyx and corolla absent. Staminate flowers: anthers dehiscing longitudinally; staminodes absent. Pistillate flowers pale green to greenish yellow; staminodes 5-8; styles indurate and spiny in fruit, incurved. Capsules many, fused at base into long-pedunculate, spheric, echinate heads, 2-beaked, glabrous, septicidal. Seeds numerous, mostly aborting, 1-2 viable in each capsule, winged. x = 16.
North America, e Asia, and Turkey.
Species 3(-4) (1 in the flora).