THAI FOREST BULLETIN (BOTANY) 36
Ecology.— Seasonal rainforest often by streams, dry evergreen forest, primary and slightly disturbed evergreen hardwood forest, swamp forest, degraded deciduous forest and bamboo, scrub roadsides; 300–800 m alt.
Notes.— Nineteen collections of M. revoluta have been seen from Thailand (11 since 1993 of which those here cited represent additional locality records) and it appears to be not uncommon. Its fruits are easily distinguished from those of all other taxa by rigid, thick-textured, strongly revolute lamellae, all uniformly interrupted along the pod midline and not extending into the marginal fruit wings which are strongly inrolled. It is vegetatively almost identical to M. interrrupta and two species with simple lamellae, M. stenoplax and
hainanensis, but is usually easily distinguished from all three by its distinctively minute
–0.2 mm rather than at least 0.4 mm), velvety, spreading pubescence on the inflorescence
axis, pedicels and calyx. Its flowers are often relatively small as in M. stenoplax and M. biplicata (Peninsular Malaysia, not recorded from Thailand) but its relatively long, broad, acute calyx lobes differ from both: in M. biplicata the calyx lobes are minute and in M. stenoplax narrow-acuminate; M. stenoplax also differs in its ultimate branchlets of the inflorescence being more distinctly lengthened. M. revoluta is often misidentified as M. interrrupta which differs in possessing thin- textured and upcurved fruit lamellae, a flat marginal wing, ultimate branchlets of the inflorescence which are always knob-like and flowers always white; flowers of M. revoluta are usually pinkish or brownish-purple (keel sometimes whitish) but two collections otherwise conforming to this species are said to have all petals white or light greenish.
Gagnepain (1916) confused two taxa in his original description of M. interrupta, citing specimens which included Harmand 272, a flowering and fruiting specimen of M. revoluta. Therefore his description includes certain characters, notably the pink flower colour, which belong to M. revoluta.
9. Mucuna interrrupta Gagnep. in H.Lecomte, Fl Indo-Chine 2 : 321. 1916, pro parte (see note above under M. revoluta); Craib, Fl .Siam 1: 444. 1928; Van Thuan, Fl. Camb. Laos Vietnam 17: 38. 1979, pro parte;Wilmot-Dear, Kew Bull. 47: 227 & Figs. 6A–J & 7A–B. 1992. Type: Cambodia [Angkor, Thorel 2098 (lectotype P!)].— M. nigricans (Lour.) Steud. var. cordata Craib, Fl .Siam 1: 444. 1928. Type: Thailand, Central, Saraburi [17 July 1925, Noe 125 (holotype K!)]. Figs. 1 N–P, 2 L–M.
Vegetatively very similar to M. stenoplax; differences as follows; stems glabrous or with sparse adpressed or abundant spreading fine hairs. Leaves with terminal leaflet to 12 by 6.5 cm, elliptic or ovate, lateral veins 5–6 pairs; hairy (rarely glabrous) both sides; stipels only 2–4 mm. Inflorescences 10–14 cm long, main axis unbranched and with few–6 knob- like ultimate branchlets towards apex, pedicels ca 10 mm, these and main axis with dense usually adpressed, pale hairs, finer than on stem; bracts very large, some usually persistent even with mature fruit and some present on lower, flowerless, part of axis, broadly ovate, acute to short-acuminate, largest towards apex, (22–) 30–40 by (7–)18–20 cm; bracteoles much longer than calyx, narrowly obovate or ± linear, acute, 22–30 by 5 cm. Calyx hairy like the axis and with irritant red bristles, narrow, tube 8 by 8–10 mm, lobes conspicuous, lowest 8–9 mm, laterals 4–6 mm long, all broadly triangular, 5–6 mm wide, broad-acute, never acuminate. Corolla white or cream, tinged purple at base, fairly large, standard 3–3.5 cm