X. FAGACEÆ.
Trees, with watery juice, slender terete branchlets marked by numerous usually pale lenticels, alternate stalked penniveined leaves, and narrow mostly deciduous stipules. Flowers monœcious, the staminate in unisexual heads or aments, composed of a 4—8-lobed calyx, and 4 or 8 stamens, with free simple filaments and introrse 2-celled anthers, the cells parallel and contiguous, opening longitudinally; the pistillate solitary or clustered, in terminal unisexual or bisexual spikes or heads, subtended by an involucre of imbricated bracts becoming woody and partly or entirely inclosing the fruit, and composed of a 4—8-lobed calyx adnate to the 3—7-celled ovary with as many styles as its cells and 1 or 2 pendulous anatropous or semianatropous ovules in each cell. Fruit a nut 1-seeded by abortion, the outer coat cartilaginous, the inner membranaceous or bony. Seed filling the cavity of the nut, without albumen; seed-coat membranaceous; cotyledons fleshy, including the minute superior radicle; hilum, basal, minute.
The six genera of this widely distributed family occur in North America with the exception of Nothofagus, separated from Fagus to receive the Beech-trees of the southern hemisphere.
CONSPECTUS OF THE NORTH AMERICAN GENERA.
Staminate flowers fascicled in globose-stalked heads; the pistillate in 2—4-flowered clusters.1. [Fagus.] Staminate flowers in slender aments. Pistillate flowers in 2—5-flowered clusters below the staminate, in bisexual aments. Nut inclosed in a prickly burr. Leaves deciduous; ovary 6-celled; nut maturing in one season; branchlets lengthening by an upper axillary bud; bud-scales 4.2. [Castanea.] Leaves persistent; ovary 3-celled; nut maturing at the end of the second season; branchlets lengthening by a terminal bud; bud-scales numerous.3. [Castanopsis.] Nut inclosed only partly in a shallow cup covered by slender recurved scales united only at the base, free above.4. [Lithocarpus.] Pistillate flowers solitary, in few-flowered unisexual spikes; nut more or less inclosed in a cup covered by thin or thickened scales, closely appressed or often free toward its rim.5. [Quercus.]