Trees or shrubs, with furrowed bark, porous brittle wood, durable in the ground, terete branchlets without terminal buds, axillary buds covered by 2 pairs of slightly imbricated scales, the outer lateral, the others accrescent, becoming oblong-ovate and acute and marking the base of the branch with narrow ring-like scars, and stout perpendicular tap-roots; producing when cut numerous stout shoots from the stump. Leaves convolute in the bud, ovate, acute, coarsely serrate, except at the base, with thin veins running to the points of the slender glandular teeth, deciduous; petioles leaving in falling small elevated semioval leaf-scars marked by an irregular marginal row of minute fibro-vascular bundle-scars; stipules ovate to linear-lanceolate, acute, scarious, infolding the leaf in the bud, caducous. Flowers opening in early summer, unisexual, strong-smelling; the staminate, in 3—7-flowered cymes, in the axils of minute ovate bracts, in elongated simple deciduous aments first appearing with the unfolding of the leaves from the inner scales of the terminal bud and from the axils of the lower leaves of the year, composed of a pale straw-colored slightly puberulous calyx deeply divided into 6 ovate rounded segments imbricated in the bud, and 10—20 stamens inserted on the slightly thickened torus, with filiform filaments incurved in the bud, becoming elongated and exserted, and ovoid or globose pale yellow anthers; the pistillate scattered or spicate at the base of the shorter persistent androgynous aments from the axils of later leaves, sessile, 2 or 3 together or solitary within a short-stemmed or sessile involucre of closely imbricated oblong acute bright green bracts scurfy-pubescent or tomentose below the middle, subtended by a bract and 2 lateral bractlets, each flower composed of an urn-shaped calyx, with a short limb divided into 6 obtuse lobes, minute sterile stamens shorter than the calyx-lobes, an ovary 6-celled after fecundation, with 6 linear spreading white styles hairy below the middle and tipped by minute acute stigmas, and 2 ovules in each cell, attached on its inner angle, descending, semianatropous. Fruit maturing in one season, its involucre inclosing 1—3 nuts, globose or short-oblong, pubescent or tomentose and spiny on the outer surface, with elongated ridged bright green ultimately brown branched spines fascicled between the deciduous scales, coated on the inner surface with lustrous pubescence, splitting at maturity into 2—4 valves; nut ovoid, acute, crowned by the remnants of the style, bright chestnut-brown and lustrous, tomentose or pubescent at apex, cylindrical, or when more than 1 flattened, marked at the broad base by a large conspicuous pale circular or oval thickened scar, its shell lined with rufous or hoary tomentum. Seed usually solitary by abortion, dark chestnut-brown, marked at apex by the abortive ovules, with thick and fleshy more or less undulate ruminate sweet farinaceous cotyledons.