THAI FOREST BULLETIN (BOTANY) 36
Ecology.— Littoral forest, estuaries, rainforest or riverbanks but always near coast and at low altitude. Its coastal distribution is partly due to the fact that its seeds can be dispersed by sea.
Conservation Status Assessment.— Least concern
Notes.— Twenty collections have been seen from Thailand (eight subsequent to 1992 of which those here cited represent additional locality records). M. gigantea is distinguished from all other Thai species in its leathery, broadly oblong, marginally winged pod with lateral faces patterned but without lamellae, its distinctly pseudumbellate inflorescence (pedicels and ultimate branchlets of varying lengths) and its often very short, broad calyx lobes and short corolla with keel only 3–4 cm long. The other subspecies (ssp. plurisemina Verdc., differing in fruit with narrower wings and 5–6 seeds, is known only from Philippines and New Guinea. The only similar species, M. acuminata, (recorded from Malaysia and Java) can be distinguished from M. gigantea by the surface patterning of its fruit being indistinct, inflorescence axis densely (rather than sparsely) pubescent and always short, long-acuminate calyx lobes, flowers which are usually longer (ca 4.5 cm) and different relative lengths of the petals, with the keel longer than wings and the standard relatively short compared to the keel. M oligoplax is somewhat similar to M. gigantea in its (indistinctly) pseudumbellate inflorescence and similarly shaped fruit but is distinguished by conspicuous red-brown indumentum on the leaves and stems and fruit faces ornamented with distinct, partly developed lamellae.
4. Mucuna oligoplax Niyomdham & Wilmot-Dear in Kew Bull. 48: 29 & Fig. 1. 1993. Type: Thailand, Peninsular, Songkhla [Nathawi, Khao Nam Khang National Park, 20 Oct. 1991 Larsen et al.42455 (holotype K!; isotypes AAU!, BKF!, L!, MO! PSU!)]. Figs. 1 D–E, 2 E.
Woody trailing plant or climber, 10–40 m long; young stems and petioles with dense, often somewhat crisped, dark red-brown, soft hairs 0.3–0.5 mm long. Leaves with terminal leaflet 12–14 by 7–8 cm, elliptic, length: width ratio 1.5–2:1, apex with short, broad acumen, base rounded, lateral veins 6–7 pairs, gently curved but abruptly looping near margin; lateral leaflets markedly asymmetrical with width ratio of abaxial: adaxial halves 2:1, base of abaxial half truncate; thin-chartaceous with ± adpressed, straight red-brown hairs, sparse above, more dense below especially on veins; stipels fairly robust, 3 mm long. Inflorescence axillary, axis very short and robust, 3–4 cm long by 1.5 mm diam. but becoming extremely thick and woody, ± 5 mm diam. in fruit, 2–3 main axes arising from same axil but each unbranched with 3(–4) ultimate branchlets which are each slightly lengthened, 2–3 mm long and spaced throughout length; pedicels very long, (2–)2.5–3.5 cm, lower ones often longer than upper ones giving inflorescence an indistinctly pseudumbellate appearance, fairly robust, 1 mm in thickness (3–4 mm in fruit), pedicels and axis with dense hairs like the stem but pale yellowish-orange; bracts and bracteoles very early caducous, bracts ovate or narrowly ovate, long-acuminate, 7 by 3.5 mm, red-brown pubescent outside. Calyx with hairs like the axis and long coarse yellowish-orange bristles, fairly broadly cup-shaped, 7– 8 by 12–14 mm; lobes very distinct, lowest 6–8 mm long, narrowly acuminate, laterals 2–3 by ± 1.5 mm. Corolla with standard pale brownish or greenish purple, ca 3 cm long; wings purple with darker veins, rather narrow 4.9–5.2 by ca 1.2 cm, apex tapering, ± acute; keel pale purple, slightly shorter than wing, ± 4.5 cm long. Fruit black, leathery, oblong, 2-seeded,