巨黧豆 ju li dou

Dolichos giganteus Willdenow, Sp. Pl. 3: 1041. 1803; Mucuna gigantea subsp. tashiroi (Hayata) Hayata; M. tashiroi Hayata.

Large climbing woody vines. Stems glabrous or with sparse fine adpressed hairs. Leaves 12-27 cm; petiole 6-14 cm, glabrous or with fine adpressed hairs; stipels linear, 3-5 mm; leaflets thinly papery, glabrous or with sparse short adpressed hairs, lateral veins 4-6 pairs, gently curved; terminal leaflet usually elliptic-ovate, sometimes rhombic or ovate, 7-16 × 4-8.5 cm, base rounded, apex indistinctly shortly acuminate; lat­eral leaflets 7-11 × 4.5-8 cm, ratio of abaxial to adaxial halves ca. 2.2:1, base rounded and oblique or slightly cordate. Inflo­rescences axillary but usually arising from rather old stems, 8-25 cm, with up to 6 nodes all clustered in upper 1/4, lower part of inflorescence without flowers or scars; bracts lanceolate to elliptic, 3-5 mm, caducous; bracteoles ovate-lanceolate, 16-18 × 5-7 mm, persistent to well-developed bud stage; ultimate peduncles and pedicels of varying lengths, 5-20 mm, progres­sively shorter near apex forming a corymb, with abundant short fine pale pubescence. Calyx with short fine pale pubescence and abundant caducous irritant bristles; tube 8-12 × 11-15 mm; lobes short and broad, lowest (1-)2-3 mm (only ca. 1/3 tube length), laterals 1-2 mm. Corolla white, tinged green, yellow, or pale pink; standard large relative to keel size, 2-3(-3.8) cm; wings 2.8-4.4 cm × 8-10 mm, slightly shorter or longer than keel; keel 3-4.2 cm. Legume oblong, 7-14 × 3-5.5 cm, ca. 5 mm thick, leathery, sparsely fine hairy and with irritant bristles, later glabrous, also ornamented with close fine raised reticulate venation giving pitted appearance, both margins thickened to prominent ribs and with pair of wings 0.5-1 cm wide. Seeds 1-3, dark brown or black, 2.3-3 × 2-2.5 cm, 8-10 mm thick; hilum black, length 2/3-3/4 of seed circumference.

Hillsides, at low elevations, often near the coast. Hainan, Taiwan [India, Japan, Malaysia, Vietnam; Australia].

Mucuna gigantea is easily distinguished from other species by the corymbose (pseudoumbellate) inflorescence with long ultimate pedun­cles and pedicels, which are all progressively markedly shorter toward the inflorescence apex; the rather persistent bracteoles; the small white flowers with very short calyx lobes; the relatively large standard; and the broadly oblong legume with reticulate surface-patterning and wide marginal wings. White-flowered variants of M. hainanensis with short, few-flowered inflorescences can be confused with M. gigantea but are distin­guished by the knoblike ultimate peduncles, the lengths and rela­tive proportions of various flower parts, with the keel and wings (but not the standard) longer, and the much longer calyx lobes, with the low­est one equaling (rather than ca. 1/3 as long as) the tube.