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.
Monoecious, the fls unisexual, in dense heads, without perianth, but mingled with small scales; staminate heads ovoid, in a terminal raceme; stamens numerous; pistillate heads solitary, long-peduncled; pistillate fls consisting of a bilocular ovary with 2 long styles; ovules orthotropous, several in each locule; frs capsular, beaked by the elongate styles, concrescent below into a globose head, each ovary with 1-2 seeds; trees with palmately veined and lobed lvs. 6, mainly N. Hemisphere.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.