Softly woody herb or small tree, 1–6 m. tall, glabrous throughout except for the calyx-margin and a few hairs on the stipules; branches less spreading than those of S. sesban. Stems usually aculeate. Stipules lanceolate, acuminate, erect, up to 12 mm. long and 3 or 4 mm. broad, rather persistent; leaf-rhachis up to 30 cm. long, usually aculeate; leaflets in up to 50 pairs, up to 24(–35) mm. long and 6(–10) mm. wide. Racemes 6–20-flowered, 11–25 cm. long, including the usually aculeate peduncle of 3–6 cm.; pedicels up to 16 mm. long in fruit. Receptacle 1.5 mm. long; calyx-tube 4–5 mm., teeth broadly acuminate, 1.5 mm. long. Corolla a deep golden-yellow, the standard usually flecked with violet; blade of standard at first widening gradually from the 2 mm. long claw and then very abruptly so that it is subcordate just below the middle, 13–15 mm. long, 17–20 mm. wide; appendages semicircular or broadly triangular without any free tips (fig. 49/5b, c, p. 332); blade of wing 10–12 mm. long, 4–7 mm. wide, hooked at the base; claw 4–6 mm. long; blade of keel 5–6 mm. long, 4 mm. wide at the base and 7–9 mm. near the apex; basal tooth large, ± parallel to the 7–8 mm. long claw (fig. 49/5a). Filament-sheath (9–) 10–13 mm. long; free parts 4–5 mm. long; anthers 0.8–0.9 mm. long. Ovary 24–32-ovulate; style glabrous, 4 mm. long. Pod curved, up to 30 cm. long, 4–5 mm. wide, 3 mm. thick at the centre, less at the sutures; septa 9–10 mm. apart (fig. 51/13, 14, p. 346). Seeds dark olive-brown, not mottled, subcylindrical, 6–6.5 × 2.5 × 2.2 mm.; hilum 0.9 mm. long.
