Vachellia bravoensis

Shrubs or trees, erect, to 4(–6) m; bark grayish brown, shallowly furrowed. Stems slightly flexuous, glabrous or sparsely pubescent, not glu­tinous; short shoots present. Leaves 5–20 mm; stipular spines terete, straight, 1–15(–29) × 0.5–1.5 mm near base; petiole 2–8 mm, usually densely pubescent; petiolar gland 1, at or just below lowermost pinnae, sessile, circular, 0.2–1.1 mm diam., donut-shaped (circular in outline with characteristic central hole); rachis 0–18 mm; pinnae 1–3(or 4) pairs, 7–28 mm; leaflets 10–24 pairs per pinna, blades flat, oblong, 2–4.2(–5) × 0.6–1.1 mm, base oblique and obtuse, apex broadly acute to obtuse, surfaces glabrous. Peduncles 7–24 mm. Inflorescences globose heads, densely flowered, 8–11 mm diam., solitary or clusters of 2–5 on short shoots; involucre at base of head (not obvious). Flowers yellow; calyx 0.8–1.6 mm, glabrous or puberulent; corolla 2–3 mm, glabrous or puberulent; filaments yellow, 3.2–4.2 mm. Legumes linear, nearly terete in cross section, 70–160 × 6–9 mm, constricted between seeds. Seeds uniseriate. 2n = 26.

Phenology: Flowering Feb–Apr.
Habitat: Disturbed sites in thorn scrub woodlands, desert grasslands.
Elevation: 0–700 m.

Distribution

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Tex., Mexico (Coahuila, Hidalgo, Nuevo León, San Luis Potosí, Tamaulipas).

Discussion

Vachellia bravoensis is known from southern Texas from Wharton County north to Blanco County, west to Kinney County, and south to Cameron County.

Many authors have placed Vachellia bravoensis with V. tortuosa because the fruits are similar, being constricted around the seeds, relatively long and narrow, and pubescent. Vachellia bravoensis is easily separated from V. tortuosa by the presence of a circular petiolar gland at or immediately below the lowermost pinna pair, and fewer pinna pairs (1–3 versus (2–)4–8).

Vachellia bravoensis hybridizes with V. rigidula (V. × ruthvenii Seigler & Ebinger). This uncommon hybrid has been found only at the Chaparral Wildlife Management Area, Dimmit County, Texas. It is similar to V. bravoensis in having some leaves with two pinna pairs and the pinnae with five to twelve pairs of leaflets.

Selected References

None.

Lower Taxa

None.