A tree, rarely 30° high, with a trunk 10′—12′ in diameter, numerous spreading branches, and striately angled puberulous or in Texas glabrous pale brown branchlets faintly tinged with red and armed with stout recurved infrastipular spines flat at base, and ¼′ long and broad. Bark of the trunk about ⅛′ thick, furrowed, the surface separating into thin narrow scales. Wood heavy, very hard, strong, close-grained, durable, rich brown or red, with thin light yellow sapwood of 5 or 6 layers of annual growth.
Distribution. Dry gravelly mesas, the sides of low cañons and the banks of mountain streams; valley of the Rio Grande, western Texas, through southern New Mexico and Arizona to southern California, ranging northward in Arizona to the rim of the Grand Cañon of the Colorado River, and to Clark County, Nevada; in northern Mexico, and in Lower California to the eastern base of the San Pedro Mártir Mountains.
4. LEUCÆNA Benth.
Trees or shrubs, with slender unarmed branches. Leaves persistent, abruptly bipinnate, with numerous pinnæ and small leaflets in many pairs, petiolate, the petioles often furnished with a conspicuous gland below the lower pair of pinnæ; stipules minute and caducous, or becoming spinescent and persistent. Flowers minute, white, mostly perfect, sessile or short-pedicellate, in the axils of small peltate bracts villose at apex, in globose many-flowered pedunculate heads, the peduncles in axillary fascicles or in leafless terminal racemes; calyx tubular-campanulate, minutely 5-toothed; petals 5, free, acute or rounded at apex, narrowed at base; stamens 10, free, inserted under the ovary, exserted; filaments filiform; anthers oblong, versatile; ovary stipitate, contracted into a long slender style, with a minute terminal slightly dilated stigma. Legume many-seeded, stipitate, linear, compressed, dehiscent, the valves thickened on the margins, rigid, thin, continuous within, their outer coat thin and papery, dark-colored, the inner rather thicker, woody, pale brown. Seeds obovoid, compressed, transverse, the hilum near the base, suspended on a long slender funicle; seed-coat thin, crustaceous, brown and lustrous; embryo inclosed on its two sides by a thin layer of horny albumen; radicle slightly exserted.
Leucæna with nine or ten species is confined to the warmer parts of America from western Texas to Venezuela and Peru, and to the islands of the Pacific Ocean from New Caledonia to Tahiti, where one species has been recognized. Of the indigenous species found in the territory of the United States, three are arborescent. Leucæna glauca L., a small tree or shrub, cultivated in all warm countries, and a native probably of tropical America, is now naturalized on Key West, Florida.
The generic name, from λευχαίνω, refers to the color of the flowers.
CONSPECTUS OF THE NORTH AMERICAN SPECIES.
Peduncles bibracteolate at apex; stipules becoming spinescent. Leaves 10—14-pinnate; pinnæ with 15—30 pairs of leaflets; blade of the bract of the flower produced into a short point.1. [L. Greggii] (E). Leaves 2—4-pinnate; pinnæ with 4—8 pairs of leaflets; blade of the bract of the flower produced into a long slender villose tip.2. [L. retusa] (E). Peduncles without bracts; stipules minute, caducous; leaves 30—36-pinnate; pinnæ with 30—60 pairs of leaflets.3. [L. pulverulenta] (E).
1. [Leucæna Greggii] S. Wats.
