5. Mucuna calophylla W. W. Smith, Notes Roy. Bot. Gard. Edinburgh. 12: 216. 1920.
美叶油麻藤 mei ye you ma teng
Climbing vines, 1-3 m. Stems up to 2 cm in diam., red-brown, young stems with abundant fine long adpressed hairs, later glabrous or glabrescent. Leaves 15-22 cm; petiole 4-12 cm; stipels not persistent; leaflets thinly papery or thicker textured, abaxially with dense silky hairs, adaxially with sparse adpressed long silvery hairs, rarely glabrescent with age, lateral veins 5 or 6, gently curved; terminal leaflet ovate, elliptic, or rhombic, 7-11.5 × 3-5 cm, relatively narrow, length 2-2.5 × width, base cuneate or rounded, apex caudate or abruptly broadly acuminate, 1-2 cm; lateral leaflets 7-10.5 cm, width ratio of abaxial to adaxial halves 1.5:1, base slightly cordate or truncate. Inflorescence axillary or from older stems, 3-12 cm, with up to 11 nodes spaced throughout length but more crowded near apex; bracts caducous, narrowly ovate, up to 3 mm; bracteoles caducous, elliptic, ovate, or slightly obovate, up to 6 mm; pedicels 4-5 mm, usually with abundant fine short adpressed silvery hairs. Calyx with dense light brown adpressed short hairs and sparse caducous reddish irritant bristles; tube 6-7 × 8-11 mm; lateral lobes 2-4 mm, lowest lobe 5-6 mm. Corolla reddish purple or deep crimson; standard 2-2.4 cm; wings 2.8-3.2 × ca. 1 cm; keel 3.5-4 cm. Legume linear-oblong, straight, ca. 13 × 1.8-3 cm, ca. 1.5 cm thick, ± woody or thickly leathery, indented between seeds, with dense reddish or pale long irritant bristles and short spreading hairs and with raised reticulate surface patterning; interior septum very thick, up to 2 mm, woody. Seeds ca. 7, oval in outline, flattened, not glossy, ca. 2 × 1.5 cm, ca. 1 cm thick; hilum brownish orange, length 1/2-3/4 of seed circumference.
● Forests, open thickets; 1000-3000 m. Yunnan.
This species is distinctive in its narrow leaflets without persistent stipels and usually densely silvery hairy abaxial surface, its small flowers, and its linear ± woody legume much smaller than the other Mucuna species with woody linear legumes. Other small linear legumes are distinguished by fleshy texture or surface lamellae.