3. ACACIA Adans.
Trees or shrubs, with slender branches armed with spinescent stipules or infrastipular spines. Leaves alternate on young branchlets and fascicled in earlier axils, bipinnate, with usually small leaflets, persistent. Flowers perfect or polygamous, small, in the axils of minute linear bractlets more or less dilated and often peltate at apex, in globose heads or cylindric spikes on axillary solitary or fascicled peduncles; calyx campanulate, 5 or 6-toothed; petals as many as the divisions of the calyx, more or less united; stamens numerous, usually more than 50, exserted, free or slightly and irregularly united at base, inserted under or just above the base of the ovary; filaments filiform; anthers small, attached on the back, versatile; ovary contracted into a long slender style terminating in a minute stigma. Legume nearly cylindric or flat, indehiscent, continuous or divided within. Seeds transverse, compressed; seed-coat thick, crustaceous, marked on each face of the seed by an oval depression or ring; radicle straight, included, or slightly exserted.
Acacia with more than four hundred species is widely distributed through Australia, where it is most largely represented, tropical and southern Africa, northern Africa, southwestern China, the warmer regions of southern Asia, the islands of the south Pacific, tropical and temperate South America, the West Indies, Central America and Mexico to the southwestern boundaries of the United States where ten or twelve species occur; of these five are arborescent. Acacia is astringent, and many species yield valuable tan bark. Gum arabic is produced by different Old World species; many of the species yield hard heavy durable wood, and some of the Australian Acacias are large and valuable timber-trees. Many species are cultivated for their graceful foliage and handsome fragrant flowers.
The generic name, from ἀκακία, relates to the spines with which the branches are usually armed.
CONSPECTUS OF THE ARBORESCENT SPECIES OF THE UNITED STATES.
Flowers in globose heads; corolla 5-lobed; ovary sessile; stipules persistent, becoming spines. Legume cylindric, glabrous, its sutures conspicuously thickened and grooved; seeds in 2 ranks.1. [A. Farnesiana] (E). Legume flattened, pubescent, its sutures not thickened, slightly grooved; seeds in 1 rank.2. [A. tortuosa] (E). Flowers in short, often interrupted, spikes; legume flattened, pubescent, its sutures thickened; seeds in one rank.3. [A. Emoriana] (E). Flowers in elongated slender spikes; corolla of 5 petals only slightly united at base; ovary stalked; stipules caducous; branchlets armed with infrastipular spines. Legume 1′—1¼′ wide, straight or slightly contracted between the seeds, not becoming twisted and contorted at maturity; seeds narrow-obovoid or ovoid; leaflets green, glabrous, with prominent veinlets.4. [A. Wrightii] (E). Legume ½′—¾′ wide, often conspicuously contracted between the seeds, becoming twisted and contorted at maturity; seeds nearly orbicular; leaflets blue-green, pubescent, with obscure veinlets.5. [A. Greggii] (E, G, H).
1. [Acacia Farnesiana] Willd. Huisache. Cassie.
Leaves 2′—4′ long, with 2—8, usually 4 or 5, pairs of pinnæ, generally somewhat puberulous on the short petiole and rachis; in Texas mostly falling at the beginning of winter; pinnæ sessile or short-stalked, remote or close together, with 10—25 pairs of linear acute leaflets tipped with a minute point, unequal at base, sessile or short-petiolulate, glabrous or puberulous, bright green, ⅛′—¼′ long. Flowers bright yellow, very fragrant, 1/16′ long, opening during the summer and autumn from the axils of minute clavate pilose bractlets, in heads ⅔′ in diameter, on axillary thin puberulous peduncles, solitary or most often 2 or 3 together and 1′—1½′ in length, with two minute dentate connate bracts forming an involucral cup immediately under the flower-head; calyx about half as long as the petals and like them somewhat pilose on the outer surface; stamens two or three times as long as the corolla; ovary short-stipitate, covered with long pale hairs. Fruit oblong, cylindric or spindle-shaped, thick, turgid, straight or curved, slightly contracted between the seeds, short-stalked, narrowed at apex into a short thick point, 2′—3′ long, ½′—⅔′ broad, dark red-purple, lustrous, and marked by broad light-colored bands along the thickened grooved sutures, the outer coat of the walls thin and papery, inclosing a thick pithy pulp-like substance surrounding the seeds, each in a separate thin-walled compartment; seeds ovoid, thick, flattened on the inner surface by mutual pressure, ¼′ long, suspended transversely in 2 ranks on a short straight funicle, light brown, lustrous, and faintly marked by large oval rings.
A tree, 20°—30° high, with a straight trunk 12′—18′ in diameter, separating 6°—8° from the ground into numerous long pendulous branches forming a wide round spreading head, and slender terete or slightly striate angled branchlets, glabrous or at first puberulous, and armed with straight rigid terete spines developed from the persistent stipules and sometimes 1½′ long. Bark of the trunk thin, reddish brown, irregularly broken by long reticulated ridges, exfoliating in large thin scales. Wood heavy, hard, close-grained, rich reddish brown, with thin pale sapwood; in India used for the knees of small vessels and in agricultural implements.
Distribution. Now widely spread by cultivation through the tropical and subtropical regions of the two worlds and probably a native of America from western Texas to northern Chile; growing in Texas apparently naturally in the arid and almost uninhabited region between the Nueces and Rio Grande; naturalized and now covering great areas in the valley of the Guadalupe River near Victoria, Victoria County, Texas.
Largely cultivated in southern Europe for its fragrant flowers used in the manufacture of perfumery, as an ornament of gardens in all warm countries, and in India as a hedge plant.
2. [Acacia tortuosa] Willd.
Leaves generally less than 1′ long, short-petiolate, with a slender puberulous rachis and usually 3 or 4 pairs of pinnæ; early deciduous; pinnæ sessile or short-stalked, remote, with 10—15 pairs of linear somewhat falcate leaflets, acute, tipped with a minute point, subsessile, light green, glabrous, 1/20′—1/16′ long. Flowers minute, bright yellow, very fragrant, in the axils of clavate pilose bracts, in heads ¼′—⅜′ in diameter, appearing in March with or just before the unfolding leaves, on clustered or solitary slender puberulous peduncles ½′—¾′ long, and furnished at apex with 2 minute connate bracts; calyx only about one third as long as the corolla, with short puberulous lobes; corolla puberulous at apex, less than half as long as the filaments; ovary covered with short close pubescence. Fruit elongated, linear, slightly compressed, somewhat constricted between the seeds, dark red-brown and cinereo-puberulous, 3′—5′ long and about ¼′ wide; seeds in 1 series, obovoid, compressed, dark red-brown, lustrous, about ¼′ long, faintly marked by large oval rings.
A tree, occasionally 15°—20° high, with a straight trunk 5′—6′ in diameter, stout wide-spreading branches forming an open irregular head, and slender somewhat zigzag slightly angled reddish brown branchlets roughened by numerous minute round lenticels, villose with short pale hairs, and armed with thin terete puberulous spines occasionally ¾′ long; in Texas usually shrubby, with numerous stems forming a symmetric round-topped bush only a few feet high. Bark dark brown or nearly black, and deeply furrowed.
Distribution. Valley of the Rio Cibolo to Eagle Pass on the Rio Grande, Maverick County, Texas; and in northern and southern Mexico, the West Indies, Venezuela, and on the Galapagos Islands; in Texas probably arborescent only on the plains of the Rio Grande near Spofford, Kinney County.
3. [Acacia Emoriana] Benth.
Leaves 3½′—4′ long, with a slender petiole and rachis, villose-pubescent early in the season, becoming nearly glabrous; and 4 or 5 pairs of pinnæ; falling late in the autumn; pinnæ on slender stalks ¼′ in length, with 5—7 pairs of oblong leaflets rounded and apiculate at apex, obliquely rounded at base, short-petiolulate, pointing forward, when they unfold densely villose above and on the margins, and hoary-tomentose below, becoming glabrous, gray-green rather darker above than below, ⅓′ long. Flowers subsessile, puberulous, in interrupted spikes, ¾′—1′ in length, densely hoary-tomentose when they first appear late in March, on villose peduncles ½′—1′ in length, and furnished near the apex with lanceolate caducous bracts; calyx about half the length of the ovate acute petals ciliate on the margins, about 1/12′ long and much shorter than the stamens; ovary stipitate, glabrous. Fruit fully grown in July, stipitate much compressed, rounded and sometimes slightly emarginate at apex, gradually narrowed and obliquely cuneate at base, with much thickened revolute undulate margins, densely pubescent early in the season, becoming puberulous, 5′ or 6′ long, 1¼′—1½′ wide and many-seeded, or nearly orbicular and 1 or 2-seeded; seeds in one series, oval, the two sides unsymmetric, obliquely pointed at base, rounded at apex, compressed, dark chestnut-brown and lustrous, ½′ long and ¼′ wide.
A tree, sometimes 25° high, usually smaller, with slender red-brown branchlets pubescent or puberulous when they first appear, becoming glabrous in their second year, and armed with small curved stipular spines; often a shrub.
Distribution. Texas; creek banks and cañons, near Montell and Uvalde, Uvalde County, and rocky banks of Devil’s River, Valverde County (E. J. Palmer).
4. [Acacia Wrightii] Benth. Cat’s Claw.
Leaves 1′—2′ long, slightly pubescent, especially on the petiole and rachis, with 1—3 pairs of pinnæ, slender petioles 1⅓′ in length, and eglandular or glandular with small convex glands, and linear acute caducous stipules 1/16′ long; pinnæ short-stalked, with 2—5 pairs of obovate-oblong leaflets, obliquely rounded and often apiculate at apex, sessile or short-petiolulate, 2 or sometimes 3-nerved, glabrous, or rarely pubescent, reticulate-veined, rigid, bright green and rather paler on the lower surface than on the upper surface, ¼′—⅚′ long. Flowers light yellow, fragrant, appearing from the end of March to the end of May, on slender pubescent pedicels from the axils of minute caducous bracts, in narrow spikes 1½′ long, often interrupted below the middle, on slender fascicled pubescent or sometimes glabrous peduncles; calyx obscurely 5-lobed, pubescent on the outer surface, half as long as the spatulate petals slightly united at base, and ciliate on the margins; stamens ¼′ long; ovary long-stalked, covered with long pale hairs. Fruit fully grown early in the summer, deciduous in the autumn, slightly falcate, compressed, stipitate, oblique at base, rounded and short-pointed at apex, 2′—4′ long, 1′—1¼′ wide, with thick straight or irregularly contracted margins and thin papery walls conspicuously marked by narrow horizontal reticulate veins; seeds narrow-obovoid, compressed, ¼′ long, suspended transversely on a long slender funicle, light brown, marked by large oval depressions.
A tree, occasionally 25°—30° high, with a short trunk 10′—12′ in diameter, spreading branches forming a low wide or irregular head, and branchlets when they first appear somewhat striately angled, glabrous, pale yellow-brown or dark red-brown, turning pale gray in their second year, and armed with occasional stout recurved infrastipular chestnut-brown spines ¼′ long, compressed toward the broad base and sharp-pointed, or rarely unarmed. Bark of the trunk about ⅛′ thick, divided by shallow furrows into broad ridges separating on the surface into thin narrow scales. Wood very heavy, hard, close-grained, bright clear brown streaked with red and yellow, with thin clear yellow sapwood of 6 or 7 layers of annual growth; valued and largely used as fuel.
Distribution. Valley of the Guadalupe River in the neighborhood of New Braunfels, Comal County, Texas, to the Sierra Madre of Nuevo Leon; most abundant and of its largest size south of the Rio Grande on dry gravelly mesas and foothills.
5. [Acacia Greggii] A. Gray. Cat’s Claw. Una de Gato.
Leaves 1′—3′ long, pubescent or puberulous, with 1—3 pairs of pinnæ, a short slender petiole furnished near the middle with a minute oblong chestnut-brown gland, and linear caducous stipules 1/16′ long; pinnæ short-stalked, with 4—5 pairs of obovate oblique leaflets rounded or truncate at apex and unequally contracted at base into a short petiolule, thick and rigid, 2—3-nerved, inconspicuously reticulate-veined, hoary-pubescent, 1/16′—¼′ long. Flowers fragrant, bright creamy yellow, in dense oblong pubescent spikes, on a peduncle ½′—⅔′ long, and fascicled usually 2 or 3 together toward the end of the branches; calyx obscurely 5-lobed, puberulous on the outer surface, half as long as the petals slightly united at base and pale-tomentose on the margins; stamens ¼′ long; ovary long-stalked, covered with long pale hairs. Fruit fully grown at midsummer and hanging unopened on the branches until winter or the following spring, compressed, straight or slightly falcate, obliquely narrowed at base into a short stalk, acute or rounded at apex, more or less contracted between the seeds, 2′—4′ long, ½′—¾′ wide, curling and often contorted when fully ripe, the valves thin and membranaceous, thick-margined, light brown, conspicuously transversely reticulate-veined; seeds nearly orbicular, compressed, dark brown and lustrous, ¼′ in diameter, marked by small oval depressions.
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.