Derris pseudomarginata Sirich.

         Lianas, basal diameter ca. 5 cm. Twigs 5–8 mm diam., lenticellate, the lower part thinly sericeous to glabrous, the upper part sericeous. Stipules ovate-triangular, 1.7–1.8 x 1.6–1.7 mm, outside thinly sericeous, margin ciliate, inside glabrous. Leaves with 5–7 leaflets, subcoriaceous. Petiole 4–6 cm long, striate, glabrous to thinly strigose; rachis 5–8 cm long, striate, glabrous to thinly strigose; pulvinus 4–8 mm long, thinly strigose. Stipellae absent. Leaflets: terminal one elliptic to obovate, 4.5–12 x 2.3–5.5 cm, length/width ratio 1.8–2.2, base obtuse, apex shortly acuminate, acumen 4–7 mm long, rounded, upper and lower surface glabrous, midrib raised in a furrow above, distinctly raised below, veins flat or slightly sunken above, raised below, 6–9 per side, 6–17 mm apart, not reaching the margin but curving towards the apex, anastomosing near the margin, venation reticulate; lateral ones mostly like terminal one, ovate to elliptic, 5–10.5 x 3–5.5 cm, length/width ratio 1.8–1.9, base obtuse to rounded; pulvinus 4–7 mm long, thinly strigose. Inflorescences axillary or terminal, Pseudoracemes/pseudopanicles, 5–17 cm long, peduncle 1–5 cm long; lateral branches 4.5–15 cm long, thinly sericeous, glabrescent. Bracts subtending brachyblasts ovate or triangular, 0.7–0.8 x 0.5–0.7 mm, outside thinly sericeous or glabrous, inside glabrous. Brachyblasts knob-like to elongate cylindrical, sometimes hardly visible, 0.3–3 mm long, thinly sericeous, bearing 2 or 3(–5) flowers. Bracts subtending flowers ovate, 0.6–0.8 x 0.4–0.6 mm, outside thinly sericeous or glabrous, inside glabrous. Pedicels 3–5.5 mm long, thinly sericeous. Bracteoles at the top of the pedicels, ovate, ca. 0.6 x 0.4 mm, outside glabrous or thinly sericeous, inside glabrous, margin ciliate. Calyx maroonish, cup-shaped, 2.5–3.5 mm high, outside thinly sericeous, margin ciliate, inside thinly sericeous in the upper part, tube 2–2.5 mm high, upper lip indistinct or with 2 short lobes, 0.2–0.4 x 2–2.5 mm; lateral lobes triangular or semi-circular, 0.3–0.5 x 1.2–1.5 mm; lower lobe triangular or semi-circular, 0.4–0.5 x 1.5–1.6 mm. Corolla whitish. Standard: claw 3–3.5 mm long; blade broadly obovate to orbicular, 4.5–5.5 x 4.5–5 mm, apex slightly emarginate, basal callosities absent, both sides glabrous. Wings: claw 3–3.5 mm long; blade elliptic, 4–4.5 x 1.5–1.7 mm, apex rounded, upper auricle 0.7–0.8 mm long, lower auricle indistinct, both sides glabrous. Keel petals: claw 2.7–3 mm long; blade boat-shaped, 4.7–5 x 1.6–2 mm, apex rounded, upper auricle indistinct, lateral pocket ca. 1 mm long, sometimes hardly visible, both sides glabrous or sometimes with scattered hairs at the apical part of the petal. Stamens monadelphous, with basal fenestrae, 8–8.5mm long, free part 2–2.5 mm long, glabrous; anthers 0.3–0.4 x ca. 0.3 mm, glabrous. Disc annular, more or less distinctly (5–)10-lobed, up to 0.2 mm high, hairy. Ovary 7–8 mm long, stipe indistinct, (thinly) sericeous; ovules 3 or 4; style 3–4mm long, thinly sericeous at base, upwards glabrous. Pods elliptic to strap-like, 3.3–8 x 2.5–3.7 cm, glabrous, with a wing along both sutures, upper wing 4–8 mm wide, lower wing 2–5 mm wide; seed chamber absent. Seeds 1 or 2 per fruit, broadly bean-shaped, flat, 15–17 x 13–14 x 0.5–1 mm; hilum subcentral, ca. 2 mm long.