2. HELIETTA Tul.
Trees or shrubs, with slender terete branchlets. Leaves opposite, long-petiolate, trifoliolate, persistent; leaflets sessile, obovate-oblong, obtuse, entire or crenate, subcoriaceous, grandular-punctate, the terminal the largest. Flowers regular, perfect, on slender bibracteolate pedicels, in terminal or axillary panicles; calyx 3 or 4-parted, the divisions imbricated in the bud, slightly united at base, persistent; petals 3 or 4, imbricated in the bud, hypogynous, oblong, concave, glandular-punctate, reflexed at maturity; stamens as many as the petals inserted under the disk; filaments shorter than the petals, slightly flattened, glabrous; anthers ovoid, cordate at base, attached on the back below the middle; disk free, cup-shaped, erect, subcorrugated, with a sinuate margin, 4-lobed, the lobes entire or crenate and opposite the petals; ovary minute, sessile, depressed, 3 or 4-lobed, glandular-verrucose or minutely pilose, the lateral lobes slightly compressed, 4-celled; styles united into a single slender column crowned by the globose 3—4-lobed stigma; ovules collateral, anatropous. Fruit obconic, composed of 3 or 4 dry woody 1-seeded indehiscent carpels with a cartilaginous endocarp and with a prominent horizontal wing, separating at maturity. Seed linear-oblong, seed-coat crustaceous, fragile, black; cotyledons straight, obtuse.
Helietta is distributed from the valley of the lower Rio Grande in Texas to Brazil and Paraguay. Four species are recognized, one species extending across the Rio Grande into western Texas.
The generic name is in honor of Lewis Théodore Hélie (1804—1867), a distinguished French physician.
1. [Helietta parvifolia] Benth.
Leaves 1½′—2′ long, with a stout slightly club-shaped petiole, at first puberulent, soon becoming glabrous, and oblong or narrow-obovate leaflets rounded or sometimes slightly emarginate at apex, gradually and regularly contracted at base, entire or slightly and remotely crenulate-serrate, yellow-green and lustrous above, paler below, conspicuously marked by black glandular dots, the terminal leaflet ½′—1½′ long, sometimes ½′ wide, and nearly twice as large as the others; persistent on the branches until early spring. Flowers appearing in April and May, on slender pedicels covered at first like the petioles and calyx with short dense pubescence, with minute acuminate early deciduous bracts, in dichotymously branched subsessile panicles on branchlets of the year from the axils of the upper leaves; petals 4, white, ovate, ⅛′ long, with scattered hairs on the outer surface, and thin scabrous margins, and four or five times longer than the 4 calyx-lobes; stamens 4; ovary 4-lobed, glandular-punctate like the slender style. Fruit ripening in October, oblong, ¼′—⅓′ long, with a rigid broad-ovate sometimes slightly falcate wing rounded at apex, ½′ long, and conspicuously reticulate-veined.
A slender tree, 20°—25° high, with a trunk 5′—6′ in diameter, rather erect branches forming a small irregular head, and slender pale branchlets covered with minute wart-like excrescences, slightly puberulous when they first appear, soon becoming glabrous, and marked during their second year by small inconspicuous leaf-scars; or a low shrub. Bark of the trunk about ⅛′ thick, covered with dark brown closely appressed scales separating in large irregular patches and leaving when they fall a smooth pale yellow surface. Wood hard, very heavy, close-grained, light orange-brown, with rather lighter colored sapwood.
Distribution. Often forming thickets of considerable extent and abundant near Rio Grande, Starr County, Texas; mesas south of the lower Rio Grande; of its largest size and tree-like in habit on the limestone ridges of the Sierra Madre of Nuevo Leon.