Derris montana Benth.

         Lianas, up to 20 m high. Bark (gray) brown, inner bark green. Twigs 3–6 mm diam., lenticellate, thinly hirsute or thinly strigose in young parts, glabrescent. Leaves with 5–13 leaflets. Stipules ovate-triangular, 1.5–3 x 1.5–3 mm, outside glabrous to thinly sericeous, inside glabrous. Petiole 3.5–11 cm long, striate, glabrous to thinly hirsute at the upper side; rachis 4.5–14.5 cm long, striate, glabrous to thinly hirsute at the upper side; pulvinus 5–11 mm long, hirsute, especially at the base. Stipellae rarely present, acicular, ca. 1 mm long. Leaflets chartaceous to subcoriaceous; terminal one elliptic to obovate, 7.5–18.5 x 4–9 cm, length/width ratio 1.8–2.3, base obtuse to rounded, apex acuminate, acumen 5–20 mm long, rounded, upper surface glabrous or with widely scattered appressed hairs, lower surface glabrous to thinly strigose, midrib flat to slightly sunken above, nerves flat above, 6–11 per side, 10–16 mm apart, curving towards the apex and almost reaching the leaf margin, venation reticulate; lateral leaflets mostly like terminal one, ovate, elliptic or obovate, 6.5–15.5 x 3.3–7.5 cm, length/width ratio 1.8–2.7; pulvinus 5–11 mm long, sericeous at base Inflorescences axillary or rarely terminal, pseudoracemes/pseudopanicles, 8–22 cm long; peduncle 1–3 cm long, glabrous to thinly strigose; lateral branches up to 20 cm long. Bracts subtending brachyblasts ovate to triangular, 1–1.7 x 0.7–1.1 mm, outside glabrous to sericeous, ciliate, inside glabrous or with some hairs at the base. Brachyblasts slender, cylindrical, 10–18 mm long, with 2 or 3 flowers at the apex. Bracts subtending flowers broadly ovate to triangular, 0.5–1.1 x 0.4–1.3 mm, outside glabrous or thinly sericeous, margin ciliate, inside glabrous. Pedicels 4– 9 mm long, glabrous or thinly sericeous. Bracteoles at the top of the pedicels, elliptic to ovate or orbicular, 0.7–1.4 x 0.6–1.3 mm, outside glabrous or thinly sericeous, margin ciliate, inside glabrous. Calyx 3.5–5 mm high, pink, maroonish or brown, outside glabrous to thinly sericeous, margin ciliate, inside glabrous, sometimes sericeous at apex; tube 3–3.5 mm high; upper lip indistinct or sometimes with 2 short semicircular lobes; lateral lobes (broadly) triangular, 0.5–1 x 2–3.5 mm; lower lobe triangular, 1–1.5 x 2–3 mm. Corolla white or pink to purplish, standard with green blotch at base. Standard: claw 2.5–3 mm long; blade broadly ovate to orbicular, 10–12 x 10–13 mm, apex emarginate, both sides glabrous or thinly ciliate at apex, basal callosities large. Wings: claw 3.5–4 mm long; blade elliptic, 8–11 x 2.5–3.3 mm, apex rounded, both sides glabrous or thinly ciliate at apex, upper auricle 0.5–1 mm long, lower auricle absent, lateral pocket 1.5–2.5 mm long, sometimes hardly visible. Keel petals: claw 4.5–5 mm long; blade boat-shaped, 8–11 x 3–3.6 mm, apex rounded, both sides glabrous or with some hairs at apex, auricle indistinct, lateral pocket 3–5 mm long. Stamens monadelphous, with basal fenestrae, 11–13 mm long, free part 3–5 mm long, glabrous; anthers 0.9–1 x 0.3–0.5 mm, glabrous, rarely with some hairs. Disc indistinct or annular, 0.5–1 mm high, glabrous. Ovary 9–10.5 mm long, outside sericeous, inside glabrous; stipe indistinct; ovules 1–4; style 6–8 mm long, sericeous in lower part. Pods woody, variable in shape and thickness, ellipsoid, ovoid or strap-like, 2–9.5 x 2–4 x 0.5–1.4 cm, glabrous, wings absent or obscurely present on both sutures, upper wing 1–2 mm wide, lower wing up to 1 mm wide; seed chamber absent. Seeds bean-shaped, 16–19 x 12 x 4–5 mm; hilum central, 2.5–3 mm long.