MUCUNA ADANS. (LEGUMINOSAE) IN THAILAND (C.M. WILMOT-DEAR)
both margins slightly convex but not constricted between each seed, 8–9 by 3.5–4 cm, markedly laterally flattened; surface with sparse red-brown hairs like the stem and dense irritant red-brown bristles and with a fine pattern of raised vein-lines resembling that of M. gigantea but coarser and shallower, also ornamented with a few transverse lamellae arising erratically but mostly close to upper margin, these of irregular size and poorly developed, never extending across more than T– of fruit surface, 1–10 mm long, 1–3 mm high: each margin with a pair of irregularly dentate wings 3–5 mm wide. Seed 2.2 by 1.8 by 1 cm, shiny light orange-brown mottled with dark brown; hilum black, extending through [ of circumference.
Thailand.— PENINSULAR: Trang [Yan Ta Khao district, 16 Dec. 1995, Mauric 41 (BKF)], Songkhla [Nathawi, Khao Nam Khang National Park, 20 Oct. 1991 Larsen et al. 42455 (holotype K!; isotypes AAU!, BKF!, L!, MO! PSU!)].
Distribution.— Endemic to peninsular Thailand Ecology.— Clearings and disturbed areas in evergreen rainforest; 150 m alt.
Notes.— M. oligoplax is apparently very rare, known only from two collections. It is similar to M. gigantea in fruit shape and somewhat in its inflorescence architecture with lengthened ultimate branchlets but M. gigantea is easily distinguished by pubescence which is pale or absent, a distinctly pseudumbellate inflorescence with flowers crowded in the distal part of the axis and pedicels markedly shorter towards apex, flowers which are greenish-white with shorter calyx lobes, pedicels and wing petals, the complete absence of fruit lamellae and seeds which are not mottled. Red-brown pubescence also distinguishes M. oligoplax from most other Thai taxa but M. macrocarpa and M. monosperma often have similar pubescence and sterile material can be misidentified. M. macrocarpa differs in its relatively narrower leaflets, the lateral ones ± truncate, stipels absent, longer inflorescences from old wood, flowers with a pubescent apical border and pod long, narrow and woody. M. monosperma has a similarly short inflorescence and short oblong leathery fruit but differs in shorter pedicels, calyx lobes and corolla, dark (rather than pale) purple petals and fruit with many well-developed lamellae; leaflets are also mostly smaller.
Mucuna monosperma DC. exWight in Hook., Bot. Misc. 2: 346. 1831; Craib, Fl. Siam. 1:
1928;Wilmot-Dear, Kew Bull. 42: 28 & Fig. 1. 1987 & 47: 217. 1992. Type: Eastern India
[March 1910, Roxburgh 276 (lectotype BM!., ?isolectotype K!)]. Figs. 1 F–G, 2 F.
Climber, stems and petioles rarely glabrescent, usually with abundant red-brown ± spreading hairs ca 0.4 mm long. Leaves with terminal leaflet 7–13(–15.5) by (3–)5–7(–9) cm, elliptic or ovate (–obovate), length/width ratio 1.5–1.8: 1, apex with abrupt short, wide acumen, base broad-cuneate or truncate, lateral veins (4–)5–6, gently curved; lateral leaflets markedly asymmetrical with width ratio of abaxial to adaxial halves 2:1, base of abaxial half rounded; membranous to thin-chartaceous, sometimes completely glabrous, more often with hairs at least beneath, those on veins red-brown spreading like the stem hairs, those elsewhere paler ± adpressed; stipels often inconspicuous, 0.5–3 mm. Inflorescences very short, 3–6 cm, often branched once or more close to base, ultimate branchlets 2–5, knob- like or rarely 3–4 mm long; pedicels only 6–10 mm, these and axis hairy like the stem and with sparse irritant bristles; bracteoles soon caducous, narrowly ovate or ± linear, 1.5–3 cm.