10. CERCIDIUM Tul.
Trees or shrubs, with stout tortuous branches, covered with bright green bark and armed with slender straight axillary spines, and minute obtuse buds. Leaves alternate, abruptly pinnate, petiolate, early deciduous; pinnæ 2 or occasionally 3, 6—8-foliolate; stipules inconspicuous or 0; leaflets ovate or obovate, without stipels. Flowers perfect in short few-flowered axillary racemes, solitary or fascicled, with minute membranaceous early deciduous bracts; calyx 5-lobed, the lobes equal, acute, reflexed at maturity, their margins scarious, slightly revolute; petals orbicular or short-oblong, unguiculate, bright yellow, the upper petal broader and longer clawed than the others, slightly auriculate at base of the blade, the claw conspicuously glandular at base; stamens 10, inserted with the petals on the margin of the disk, free, slightly declinate, exserted; filaments filiform, pilose below, the upper filament enlarged at base and gibbous on the upper side; anthers uniform, ovoid, versatile; ovary short-stalked, inserted at the base of the calyx-tube; styles slender, involute, infolded in the bud, with a minute terminal stigma; ovules suspended from the angle of the ovary opposite the posterior petal. Legume linear-oblong, compressed or somewhat turgid, straight or slightly contracted between the seeds, thickened on the margins, the ventral suture acute, or slightly grooved, tipped with the remnants of the style, tardily dehiscent, 2-valved, the valves membranaceous or subcoriaceous, obliquely veined. Seeds suspended longitudinally on a long slender funicle, ovoid, compressed, the minute hilum near the apex; seed-coat thin, crustaceous; embryo compressed, light green, covered on the sides only by a thin layer of horny albumen; cotyledons oval, flat, rather fleshy; radicle very short, erect, near the hilum.
Cercidium is confined to the warmer parts of the New World, where it is distributed with four or five species from the southern borders of the United States through Mexico, Central America, and Venezuela to Mendoza. Of the three species found within the territory of the United States two are small trees.
Cercidium produces hard wood sometimes used as fuel.
The generic name, from κερκίδιον, refers to the fancied resemblance of the legume to the weaver’s instrument of that name.
CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT SPECIES.
Legume compressed, with straight margins; leaflets green, slightly glandular.1. [C. floridum] (E). Legume somewhat turgid, the margins often slightly contracted between the seeds; leaflets glaucous.2. [C. Torreyanum] (G, H).
1. [Cercidium floridum] Benth. Green-barked Acacia.
Leaves 1′—1½′ long, with 2 or rarely 3 pinnæ, a broad pubescent petiole and rachis, and oval or somewhat obovate dull green puberulous minutely glandular leaflets about 1/16′ in length, rounded or slightly emarginate at apex, and when they unfold covered on the lower surface with scattered white hairs; petiolules short, stout, pubescent; appearing in April and deciduous in October. Flowers opening with the leaves, and produced in successive crops during three or four months, ¾′ in diameter, on slender pedicels, in 4 or 5-flowered racemes 1½′—2′ long, with small acute minute membranaceous caducous bracts. Fruit compressed, oblong, straight or slightly falcate, acute, narrowly and acutely margined on the ventral suture, glabrous, 2 or 3-seeded, 2′—2½′ long, ½′ broad, tardily dehiscent, the valves papery, yellow tinged with brown on the outer surface, and bright orange color within; seeds ⅓′ long.
A tree, 18°—20° high, with a short crooked trunk 8′—10′ in diameter, stout spreading branches covered with thin smooth bright green bark, forming a low wide head, and branchlets light or dark olive-green, slightly puberulous at first, soon glabrous, marked by occasional black lenticels, and armed with slender spines 1′ or less in length. Bark 1/16′ thick, light brown tinged with red, with numerous short horizontal light gray ridge-like excrescences. Wood light, soft, close-grained, pale yellow tinged with green, with thick lighter colored sapwood.
Distribution. Shores of Matagorda Bay to Hidalgo and Valverde Counties, Texas, and in northern Mexico; not common in Texas; very abundant and a conspicuous feature of vegetation in Mexico from the mouth of the Rio Grande to the foothills of the Sierra Madre.
2. [Cercidium Torreyanum] Sarg. Green-barked Acacia. Palo Verde.
Leaves few and scattered, 1′ long, hoary-tomentose when they first appear, puberulous at maturity, with a slender petiole and 2 pinnæ, with 2 or 3 pairs of oblong obtuse glaucous leaflets narrowed toward the somewhat oblique base, 1/12′—⅙′ long; unfolding in March and April and falling almost immediately when fully grown. Flowers ¾′ in diameter, on slender pedicels ¾′—1′ long, in 4 or 5-flowered racemes about 1′ in length, with small acute membranaceous caducous bracts. Fruit ripening and falling in July, 3′—4′ long, ¼′—⅓′ wide, 2—8-seeded, slightly turgid, often somewhat contracted between the seeds, frequently grooved on the ventral suture; seeds turgid, ⅓′ long.
A low intricately branched tree, leafless for most of the year, 25°—30° high, with a short often inclining trunk 18′—20′ in diameter, stout spreading branches covered with yellow or olive-green bark, forming a wide open irregular head, and glabrous slightly zigzag light yellow or pale olive-green and glaucous branchlets armed with thin straight or curved spines ¼′ long. Bark thin, smooth, pale olive-green, becoming near the base of old trunks reddish brown, ⅛′ thick, furrowed and separating into thick plate-like scales. Wood heavy, not strong, soft, close-grained, light brown, with clear light yellow sapwood.
Distribution. Sides of low cañons and depressions, and sandhills of the desert; valley of the lower Gila River, Arizona, to the Colorado Desert of southern California, and southward into Sonora and Lower California; when in flower in early spring the conspicuous and most beautiful feature of the vegetation of the Colorado Desert.