1. BURSERA Jacq.
Trees, with balsamic resinous juices. Leaves unequally pinnate; leaflets opposite, petiolulate, entire or subserrate, thin, or coriaceous. Flowers polygamous, small, on fascicled or rarely solitary pedicels, in short or elongated lateral simple or branched panicles; calyx minute, membranaceous; petals inserted on the base of an annular crenate disk, reflexed at maturity above the middle; stamens inserted on the base of the disk; anthers oblong, attached on the back above the base, usually effete in the pistillate flower; ovary sessile, ovoid, 3-celled, rudimentary in the staminate flower; style short; stigma capitate, obtuse, 3-lobed; ovules suspended below the apex from the central angle. Fruit with a valvate epicarp, globose or oblong-oblique, indistinctly 3-angled; flesh coriaceo-carnose, 2—3-valved; nutlets 1—3, usually solitary, adnate to a persistent fleshy axis, 1-celled, 1-seeded, covered with a thin membranaceous coat. Seed ovoid, without albumen; seed-coat membranaceous; hilum ventral, below the apex; embryo straight; cotyledons contortuplicate.
Bursera with about forty species is confined to southern Florida, the Antilles, the southwestern United States and to Mexico, and Central and South America.
The generic name is in honor of Joachim Burser (1593—1649), a German botanist and physician.
CONSPECTUS OF THE ARBORESCENT SPECIES OF THE UNITED STATES.
Leaves 5—7 rarely 3-foliolate, their rachis and petiole without wings; staminate flowers in elongated many-flowered racemes.1. [B. Simaruba] (D). Leaves usually 10—22-foliolate, their rachis and petiole wing-margined; staminate flowers in short, usually 3-flowered clusters.2. [B. microphylla] (G, H).
1. [Bursera Simaruba] Sarg. Gumbo Limbo. West Indian Birch.
Leaves confined to the end of the branchlets, 6′—8′ long, 4′—8′ wide, with a long slender petiole, and usually 5, rarely 3 or 7 leaflets coriaceous at maturity, oblong-ovate, oblique at base, contracted at apex into a long or short point, 2½′—3′ long, 1½′—2′ broad, with stout petiolules often ½′ long; deciduous in early winter or occasionally persistent until the following spring. Flowers about 3/16′ in diameter, appearing before the leaves or as they unfold, on slender pedicels ⅓′—½′ long, in slender raceme-like panicles, those of the staminate plant 4′—5′ long or nearly twice as long as those of the pistillate plant; calyx-lobes and petals 5; petals ovate-lanceolate, acute, revolute on the margins, and nearly four times as long as the slender acute calyx-lobes; stamens of the staminate flower as long as the petals and in the pistillate flower not more than half as long, with smaller often effete anthers. Fruit in short raceme-like clusters, ¼′—⅓′ long, 3-angled, with a thick dark red outer coat, separating readily into 3 broad-ovate valves, and containing 1 or rarely 2 bony triangular nutlets rounded at base, pointed at apex, and covered with a thin membranaceous light pink coat; seeds 1 or 2, triangular, rose color.
A glabrous tree, 50°—60° high, with a trunk 2½°—3° in diameter, massive primary branches spreading nearly at right angles, and stout terete branchlets light gray during their first season, becoming during their second year reddish brown, covered with lenticular spots and conspicuously marked by large elevated obcordate yellow leaf-scars. Winter-buds short, rounded, obtuse, with broad-ovate dark red scales slightly scarious on the margins. Bark of the trunk and large branches 1′ thick, glandular dotted, separating freely into thin papery bright red-brown scales exposing in falling the dark red-brown or gray inner bark. Wood spongy, very light, exceedingly soft and weak, light brown, with thick sapwood, soon becoming discolored by decay. Pieces of the trunk and large branches set in the ground soon produce roots and grow rapidly into large trees. The aromatic resin obtained by incisions cut in the trunk was formerly used in the treatment of gout, and in the West Indies is manufactured into varnish. An infusion of the leaves is sometimes used in Florida as a substitute for tea.
Distribution. Florida, from Cape Canaveral to the southern keys, and on the west coast from Terra Ceia Island, Manatee County, Plagida, De Sota County, and Gasparilla Island southward; one of the largest and most common of the south Florida trees, and the only one which sheds its foliage during the autumn and winter; on most of the West Indian islands, in tropical Mexico, Guatemala, New Granada, and Venezuela.
2. [Bursera microphylla] A. Gray.
Leaves glabrous, deciduous, 1′—1¼′ long, with a slender narrowly winged rachis and petiole and usually 10—20 oblong or oblong-obovate leaflets rounded at apex, obliquely cuneate at base, sessile, about ¼′ long and 1/12′ wide. Flowers appearing in June before the leaves, ⅙′ long on slender pedicels from the axils of minute acuminate caducous bracts, in mostly 3-flowered clusters ¼′ in length; staminate, calyx-lobes ovate, acute; petals 5, lanceolate, acuminate, revolute on the margins, 3 or 4 times longer than the calyx-lobes, white; stamens shorter than the petals; pistillate flower not seen. Fruit ripening in October, ellipsoid or slightly obovoid, solitary, drooping on the thickened pedicel ⅕′ in length, 3-angled, ¼′ long, red, glabrous, splitting into three valves; nutlets usually ovoid, acute, narrow at base, thin walled, 3-angled, gray with a deep depression at base.
A tree, rarely 10°—12° high, with a short trunk 2½′—3′ in diameter, stout erect and spreading branches, forming a wide round-topped head, and slender glabrous red branchlets, roughened during their first year by the crowded scars of fallen leaves; more often a low shrub. Bark of the trunk pale yellow, separating into membranaceous scales, the outer layer thin and firm, the inner layer corky, reddish brown, ½′ thick. Wood hard, close-grained, pale yellow.
Distribution. Colorado Desert, between Fish Creek and Carriso Creek about twenty-five miles from the Mexican Boundary, on “banks of dry washes, in hard sterile soil covered with boulders” (E. H. Davis), Imperial County, California; near Maricopa, Pinal County, Arizona, and in Lower California and Sonora; reported as a tree only from California.