Vigna (Lasiospron) (Benth.) Marechal, Mascherpa & Stainier

Delgado-Salinas, Alfonso, Lavin, Matt, Snak, Cristiane & Lewis, Gwilym P., 2022, Systematics of Vigna subgenus Lasiospron (Leguminosae: Papilionoideae: Phaseolinae), Systematic Botany (Basel, Switzerland) 47 (1), pp. 97-124 : 107

KEY TO THE SPECIES OF VIGNA SUBG. LASIOSPRON

1. Stipules scarcely to distinctly bilobed, below the point of insertion............................................................................. 2

2. Upper extension of stipules 3 mm long; calyx 2–2.5 mm long; flowers pale greenish yellow, 8–10 mm long; style not extended beyond stigma, stigma apically placed; pollen brush 1 mm long, with hairs curled; fruit flattened..............................................1. Vigna juruana

2. Upper extension of stipules 3–12 mm long; calyx 3–10 mm long; flowers orange to golden yellow, 12–35 mm long; style extended beyond stigma, stigma laterally placed, pollen brush 3–6 mm long, hairs spreading; fruit flattened or cylindrical............................................. 3

3. Upper extension of stipules 2–4 mm wide, membranaceous to chartaceous, up to 10-veined; calyx 3–3.5 mm long; inflorescence rachis with 2–3 nodes; style extension projecting into a small crustaceous horn-like appendage; ovules 8–10 per ovary; pods oblong, flattened, thin-valved; seed without rim-aril..................................................................................... 2. Vigna diffusa

3. Upper extension of stipules 1–2 mm wide, chartaceous, up to 6-veined; calyx 4–10 mm long; inflorescence rachis with 3–8 nodes; style-extension projecting into a horny, hook-like appendage; ovules 10–18 per ovary; pods linear to slightly falcate, cylindrical, thick-valved; seed with rim-aril............................................................................................................... 4

4. Inflorescence rachis with 2–4 nodes; calyx 4–5 ˟ 2–3 mm, sparsely hirsute to strigose at base, upper teeth slightly divided, narrow and acute, not forming a lip; keel-beak not quite completing one coil; pods linear to slightly falcate, 4–8 ˟ 0.5 cm, tapering to the apex, rostrum ca. 5 mm long........................................................................................ 3. Vigna longifolia

4. Inflorescence rachis with (3–)5–8(–9) nodes; calyx 5.5–10 ˟ 3.5–8 mm, densely hirsute-strigose, upper teeth deeply divided and broadly rounded at apex to form a lip; keel beak fully completing one coil; pods linear-oblong, 6–9 ˟ 0.7–1.1 cm, abruptly truncate at the tip, rostrum 2–3 mm long.........................................................................................4. Vigna lasiocarpa

1. Stipules distinctly spurred, below the point of insertion....................................................................................... 5

5. Inflorescence rachis with 4–6 nodes, nodes oblong, spatuliform, orifice distribution scalariform, with transverse separations; calyx 1.5–2 mm long, teeth 0.5 mm long; flower 8–12 mm long; pollen brush 2–3 mm long; pod oblong, flattened, (3–) 3.5–4 cm long, 7–8 mm wide, ascending............................................................................ 5. Vigna trichocarpa

5. Inflorescence rachis with 3–5(–8) nodes, nodes subspherical, obpyriform, orifice distribution sparse-alternate, without transverse separations; calyx 3–4 mm long, teeth 1 mm long; flower 12–14 mm long; pollen-brush 3.5–4 mm long; pod linear, subcylindrical, 4–6 cm long, ca. 6 mm wide, patent or ascending............................................................................................................ 6. Vigna schottii