VIII. JUGLANDACEÆ.
Aromatic trees, with watery juice, terete branchlets, scaly buds, the lateral buds often superposed, 2—4 together, and alternate unequally pinnate deciduous leaves with elongated grooved petioles and without stipules, the leaflets increasing in size from the lowest upward, penniveined, sessile, short-stalked or the terminal usually long-stalked. Flowers monœcious, opening after the unfolding of the leaves, the staminate in lateral aments and composed of a 3—6-lobed calyx in the axil of and adnate to an ovate acute bract, and numerous stamens inserted on the inner and lower face of the calyx in 2 or several rows, with short distinct filaments and oblong anthers opening longitudinally; the pistillate in a spike terminal on a branch of the year and composed of a 1—3-celled ovary subtended by an involucre free toward the apex and formed by the union of an anterior bract and 2 lateral bractlets, a 1 or 4-lobed calyx inserted on the ovary, a short style with 2 plumose stigmas stigmatic on the inner face, and a solitary erect orthotropous ovule. Fruit drupaceous, the exocarp (husk) indehiscent or 4-valved, inclosing a thick- or thin-shelled nut divided by partitions extending inward from the shell, and like the shell more or less penetrated by internal longitudinal cavities often filled with dry powder. Seed solitary, 2-lobed from the apex nearly to the middle, light brown, its coat thin, of 2 layers, without albumen; cotyledons fleshy and oily, sinuose or corrugated, 2-lobed; radicle short, superior, filling the apex of the nut. Of the six genera of the Walnut family two occur in North America.
CONSPECTUS OF THE NORTH AMERICAN GENERA.
Aments of staminate flowers simple; husk of the fruit indehiscent; nut sculptured; pith in plates.1. [Juglans.] Aments of staminate flowers branched; husk of the fruit 4-valved; nut not sculptured; pith solid.2. [Carya.]