The genus is represented by a single species of the southeastern United States.
The generic name is in honor of Charles Cotesworth Pinckney (1746—1825) of South Carolina, the Revolutionary patriot.
1. [Pinckneya pubens] Michx. Georgia Bark.
Leaves unfolding in March, 5′—8′ long, 3′—4′ wide; petioles ⅔′—1½′ in length. Flowers 1½′ long appearing late in May and early in June, in open clusters 7′—8′ across, their petaloid calyx-lobes sometimes 2½′ long and ½′ wide. Fruit ripening in the autumn 1′ long and ⅔′ wide; seeds with their wings about ½′ long and ⅓′ wide.
A tree, 20°—30° high, with a trunk occasionally 8′—10′ in diameter, slender spreading branches forming usually a narrow round-topped head, and branchlets coated when they first appear with hoary tomentum soon turning light red-brown, pubescent during the summer, and slightly puberulous during their first winter, ultimately becoming glabrous. Winter-buds: terminal ovoid, terete, ½′ long, contracted above the middle into a slender point, and covered by the dark red-brown lanceolate acute stipules of the last pair of leaves of the previous year, often persistent at the base of the growing shoots and marked at the base by 2 broadly ovate pale scar-like slightly pilose elevations; axillary buds obtuse, minute, nearly immersed in the bark. Bark of the trunk about ¼′ thick, with a light brown surface divided into minute appressed scales. Wood close-grained, soft, weak, brown, with lighter-colored sapwood of 8—10 layers of annual growth. The bark has been used in the treatment of intermittent fevers.
Distribution. Low wet sandy swamps on the borders of streams; coast region of South Carolina through southern Georgia and northern Florida to the valley of the lower Apalachicola River; rare and local.
2. EXOSTEMA Rich.
Trees or shrubs, with terete branchlets, and bitter bark. Leaves sessile or petiolate, persistent; stipules interpetiolar, deciduous. Flowers axillary and solitary or in terminal pedunculate cymes, fragrant, the peduncle bibracteolate above the middle; calyx-tube ovoid, clavate or turbinate, the limb short, 5-lobed, the lobes nearly triangular, persistent; corolla 5-lobed, white, salver-form, the tube long and narrow, erect, the lobes of the limb linear, elongated, spreading, imbricated in the bud; filaments filiform, exserted, united at base into a tube inserted on and adnate to the tube of the corolla; anthers oblong-linear; ovary 2-celled; style elongated, slender, exserted; stigma capitate, simple or minutely 2-lobed; ovules numerous, attached on the 2 sides of a fleshy oblong peltate placenta fixed to the inner face of the cell, ascending. Fruit a many-seeded 2-celled capsule septicidally 2-valved, the valves 2-parted, their outer layer membranaceous, separable from the crustaceous inner layer. Seeds compressed, oblong, imbricated downward on the placenta; seed-coat chestnut-brown, lustrous, produced into a narrow wing; embryo minute, in fleshy albumen; cotyledons flat; radicle terete, inferior.
Exostema with about twenty species is confined to the tropics of America, and is most abundant in the Antilles, one species reaching the shores of southern Florida. The bark contains active tonic properties, and has been used as a febrifuge.