Altogether glabrous shrub or small tree 2–3 m. high with pole-like stem and short lateral branches giving plant a columnar appearance; bark buff or fawn. Young branchlets pale grey, sometimes going brown; epidermis flaking away later to expose a powdery rusty-brown inner layer. Stipules spinescent, mostly 1.5–3.5(–5.5) cm. long, straight, mostly grey or whitish, some fused at base into round or ovoid “ant-galls” 1–2.5 cm. in diameter, which are purplish going black and characteristically spotted or flecked. Leaves: petiole 3–13 mm. long, frequently glandular at apex; rhachis 0–3.2 cm. long; pinnae 1–4 pairs, 2–4.5 cm. long; leaflets 7–16 pairs, acute or subacute and mucronate at apex, (4–)5–13(–17) mm. long, 1.5–4 (–6) mm. wide. Flowers creamy-white, in heads; involucel at base of peduncle. Calyx 1.75–3 mm. long. Corolla 4.5–5 mm. long. Pods (Fig. 17/54, p. 68) short, half-moon-shaped or reniform, flattened, thin, glabrous, finely net-veined, grey-brown, 1.5–4 cm. long, 1–1.7 cm. wide, one-seeded. Seeds grey, mottled with dark brown, smooth, subcircular or broadly elliptic, compressed, 9–11 mm. long, 8.5–9 mm. wide; areole 5–7 mm. long, 4–6 mm. wide.
