Vachellia constricta
Phytologia 87: 152. 2006. name conserved
Shrubs or trees, erect, to 6 m; bark dark gray, smooth or shallowly furrowed. Stems not flexuous, glabrous or pubescent, not glutinous; short shoots present. Leaves 12–35(–40) mm; stipular spines terete, straight, 5–15(–38) × 0.8–1.2 mm near base; petiole 4–14 mm, sparsely puberulent; petiolar gland 1, at or just below lowermost pinnae, usually sessile, rarely short-stalked, circular, 0.2–0.7 mm diam., donut-shaped; rachis 6–35 mm; pinnae 2–8 pairs, 5–12 mm; leaflets 5–12 pairs per pinna, blades flat, elliptic to oblong or oval, 1.5–3.6 × 0.7–1.3 mm, base oblique and obtuse, apex obtuse to acute, surfaces usually glabrous. Peduncles 11–26 mm. Inflorescences globose heads, densely flowered, 5.5–9.5 mm diam., solitary or clusters of 2–5 on short shoots; involucre near middle of peduncle. Flowers pale yellow; calyx 0.9–1.4 mm, glabrous; corolla 1.7–2.4 mm, glabrous; filaments yellow, 3.5–5 mm. Legumes linear, flattened, 50–150 × 3.6–5.6 mm, constricted between seeds. Seeds uniseriate. 2n = 52.
Phenology: Flowering Apr–Oct.
Habitat: Thorn scrub woodlands, deserts, disturbed and arid sites.
Elevation: 100–2000 m.
Distribution
Ariz., N.Mex., Tex., Mexico (Baja California Sur, Chihuahua, Coahuila, Durango, Nuevo León, Oaxaca, Puebla, Querétaro, San Luis Potosí, Sonora, Tamaulipas, Veracruz, Zacatecas).
Discussion
In Texas, Vachellia constricta is found in the westernmost part of the state, from El Paso County eastward to Loving and Brewster counties; it is also disjunct in Howard and Midland counties.
Vachellia constricta is closely related to V. vernicosa. Vachellia vernicosa has glutinous leaves, twigs, and fruits, is mostly glabrous throughout, and has 1 or 2(or 3) pinna pairs; V. constricta is without glutinous leaves, twigs, and fruits, usually is pubescent, and has leaves with 2–8 pinna pairs. A nearly spineless form appears to be common in Arizona and New Mexico (var. paucispina). The variation existing in individuals as well as within populations suggests that this characteristic represents random variation, and these plants do not merit varietal status.
Selected References
None.