Leaves 9′—12′ long, with slender villose pubescent petioles and rachis, and 15—19, usually 19, ovate-lanceolate to lanceolate long-pointed often slightly falcate leaflets, serrate with remote teeth except toward the usually rounded cuneate or rarely cordate base, thin, puberulous above while young, becoming bright green, lustrous and glabrous on the upper surface, below furnished with conspicuous tufts of pale hairs, and villose-pubescent along the midrib and primary veins, 2½′—4′ long and ¾′—1′ wide. Flowers: staminate in slender glabrous or sparingly villose aments 3′—5′ long; calyx elongated, coated like its bract with scurfy pubescence, divided into 5 or 6 acute lobes; stamens 30—40, with short connectives bifid at apex; ovary of the pistillate flower oblong-ovoid, thickly covered with villose pubescence, ⅛′ long, the border of the thin bract and bractlets much shorter than the calyx-lobes; stigma yellow. Fruit globose, 1¼′—2′ in diameter, with a thin dark-colored husk covered with short soft pubescence; nut nearly globose, somewhat flattened at the ends, faintly grooved with remote longitudinal depressions, thick shelled; seed small and sweet.
A tree usually 30°—40°, occasionally 75° high, with a tall trunk 1°—2° in diameter, stout pendulous branches forming a narrow round-topped head, and comparatively slender branchlets thickly coated when they first appear with villose pubescence, reddish brown and puberulous, and marked by pale lenticels and small elevated obscurely 3-lobed leaf scars during their first winter, becoming darker and nearly glabrous in their second year. Winter-buds coated with hoary tomentum; terminal acute, compressed, more or less enlarged at apex, ¼′—⅓′ long; axillary usually solitary, nearly globose, about 1/16′ in diameter. Bark gray-brown, smoothish, longitudinally fissured into narrow plates. Wood heavy, hard, rather coarse-grained, dark brown often mottled, with thick pale sapwood of from 8 to 10 layers of annual growth.
Distribution. Coast region of central California; banks of the lower Sacramento River; along streams near the western base of Mt. Diablo, and on eastern slope of the Napa Range near Atlas Peak east of Napa Valley; near Loyalton in the Sierra Valley.