Trees, with stout unarmed blunt branchlets with a thick pith, prolonged by axillary buds, rough deeply fissured bark, thick fleshy roots, and minute buds depressed in pubescent cavities of the bark, 2 in the axil of each leaf, superposed, remote, the lower and smaller sterile and nearly surrounded by the enlarged base of the petiole, their scales 2, ovate, rounded at apex, coated with thick dark brown tomentum, infolded one over the other, accrescent with the young shoots. Leaves deciduous, unequally bipinnate; pinnæ many-foliolulate, with 1 or 2 pairs of the lowest pinnæ reduced to single leaflets; pinnæ and leaflets usually alternate; leaflets thin, ovate, entire, petiolulate; stipules foliaceous, early deciduous. Flowers regular, diœcious, greenish white, long-pedicellate, the slender pedicels from the axils of long lanceolate scarious caducous bracts, bibracteolate near the middle; staminate flowers in a short terminal racemose corymb; pistillate flowers in elongated terminal racemes, on pedicels much longer than those of the staminate flowers; calyx tubular, elongated, 10-ribbed, lined with a thin glandular disk, 5-lobed, the lobes, lanceolate, acute, nearly equal, erect; petals 4 or 5, oblong, rounded or acute at apex, pubescent, as long as the calyx-lobes or rather longer and twice as broad, inserted on the margin of the disk, spreading or reflexed; stamens 10, free, inserted with the petals, erect, included; filaments filiform, pilose, those opposite the petals shorter than the others; anthers oblong, uniform, small and sterile in the pistillate flower; ovary sessile or slightly stipitate, acute; styles short, erect, obliquely dilated into 2 broad lobes stigmatic on their inner surface, rudimentary or 0 in the sterile flower; ovules numerous, suspended from the angle opposite the posterior petals. Legume oblong, subfalcate, turgid or slightly compressed, several-seeded, 2-valved, tardily dehiscent, the thin tough woody valves thickened on the margins into narrow wings, pulpy between the seeds. Seeds ovoid or slightly obovoid, suspended by a long slender funicle; seed-coat thick, bony, brown and opaque, of 3 layers; embryo surrounded by a thin layer of horny albumen; cotyledons ovate, orange-colored, thick and fleshy, the radicle short, erect.
Gymnocladus, with two species, is confined to eastern North America and to central China.
Gymnocladus is slightly astringent and purgative, and the detersive pulp surrounding the seeds of the Asiatic species is used in China as a substitute for soap.
The generic name, from γυμνός and κλάδος, relates to the stout branchlets destitute of spray.
1. [Gymnocladus dioicus] K. Koch. Kentucky Coffee-tree. Mahogany.
Leaves 1°—3° long, 18′—24′ wide, obovate, 5—9 pinnate, the pinnæ 6—14-foliolate, covered when they unfold with hoary tomentum except on the upper surface of the ovate acute leaflets, often mucronate, especially while young, cuneate or irregularly rounded at base, pink at first, soon becoming bronze-green and lustrous, glabrous on the upper surface with the exception of a few scattered hairs along the midrib, and at maturity thin, obscurely veined, dark green above, pale yellow-green and glabrous below, with the exception of a few short hairs scattered along the narrow midrib, 2′—2½′ long and 1′ wide, or those replacing the lowest or occasionally the 2 lower pairs of pinnæ sometimes twice as large; turning bright clear yellow in the autumn before falling; petioles abruptly and conspicuously enlarged at base, at first hoary-tomentose, becoming glabrous at maturity; stipules lanceolate or slightly obovate, glandular-serrate toward the apex, ⅓′ long. Flowers: inflorescence of the staminate tree 3′—4′ long, the lower branches usually 3 or 4-flowered; inflorescence of the pistillate tree 10′—12′ long, the flowers on stout pedicels 1′—2½′ long or twice to five times as long as those of the staminate flowers; flowers hoary-tomentose in the bud; calyx ⅔′ long, covered on the outer surface when the flowers open with pale hairs and on the inner surface with hoary tomentum; petals keeled, pilose on the back, slightly grooved, tomentose on the inner surface; anthers bright orange color; ovary hairy. Fruit 6′—10′ long, 1½′—2′ wide, dark red-brown, covered with a glaucous bloom, on stout stalks 1′—2′ in length, remaining unopened on the branches through the winter; seeds separated by a thick layer of dark-colored sweet pulp, ¾′ long.
A tree, 75°—110° high, with a trunk 2°—3° in diameter, usually dividing 10°—15° from the ground into 3 or 4 principal stems spreading slightly and forming a narrow round-topped head, or occasionally sending up a tall straight shaft destitute of branches for 70°—80°, and branchlets coated when they first appear with short dense pubescence faintly tinged with red, bearing at their base the conspicuous orange-green obovate pubescent bud-scales, ¼′—⅓′ thick at the end of their first season, very blunt, dark brown, often slightly pilose, marked by orange-colored lenticels, and roughened by the large pale broadly heart-shaped leaf-scars displaying the ends of 3 or 4 conspicuous fibro-vascular bundles. Bark of the trunk ¾′—1′ thick, deeply fissured, dark gray tinged with red, and roughened by small persistent scales. Wood heavy although not hard, strong, coarse-grained, very durable in contact with the soil, rich light brown tinged with red, with thin lighter colored sapwood of 5 or 6 layers of annual growth; occasionally used in cabinet-making and for fence-posts, rails, and in construction. The seeds were formerly used as a substitute for coffee; a decoction of the fresh green pulp of the unripe fruit is used in homœopathic practice.
Distribution. Bottom-lands in rich soil; central and western New York and Franklin County, Pennsylvania, through southern Ontario and southern Michigan to southeastern Minnesota, northeastern and southern Iowa, southeastern South Dakota, eastern and northeastern Nebraska, eastern Kansas, southwestern Arkansas and northeastern Oklahoma (with isolated stations in Woods and Custer Counties and in the western parts of Cimarron County); in Eastern Kentucky, and western and middle Tennessee; nowhere common.
Occasionally cultivated in the gardens and parks of the eastern United States, and of northern and central Europe.