Twining annual herbs. Stems terete, up to 2 m long, covered with 1-3 mm long, retrorse or spreading bulbous based hairs. Leaves 3-foliolate; petioles 3-5(-7) cm long, densely covered with retrorse or spreading bulbous based hairs; stipules elliptically lanceolate, medifixed, 7-9 mm long, 5-7 nerved, rounded at base, acute at apex, hairy on dorsal surface; stipels 2, linear-lanceolate, 2-3 mm long, acute or acuminate at apex, glabrous. Leaflets membranous, entire; lateral ones obliquely ovate or rhomboid to lanceolate, 2.2-5.5 x 1.5-2.3 cm, obliquely rounded at base, acute or shortly acuminate at apex, sparsely hairy; terminal leaflet ovate or rhomboid-lanceolate, 3-6.4 x 1.2-4 cm, base rounded (not oblique as in lateral leaflets), apex acute or shortly acuminate, sparsely hairy, margins entire or sometimes wavy; rachis 2-10 mm long, densely covered with whitish hairs. Flowers are of two kinds; the chasmogamous flowers present on leafy aerial shoots while cleistogamous flowers present on leafless subterranean shoots, which are close to soil surface. Chasmogamous flowers: yellow, 2-4 in axillary and terminal pseudo-racemes; peduncle 5-7.5 cm long, densely hairy with whitish-brown, 1-1.5 mm long, retrosely spreading hairs; pedicels 2-2.5 mm long, densely hairy as peduncle; bracts lanceolate, 2.5-3 x 0.8-1 mm, herbaceous, acute at apex, densely hairy; bracteoles 2, linear, 4-4.5 mm long, densely hairy. Calyx campanulate, ca 2 mm long; teeth triangular, 0.2-1.2 x 0.7-1 mm, sparsely hairy along margins. Standard petal yellow, asymmetrical, broadly ovate, 6-6.5 x 7.5-8.5 mm, emarginate at apex, central protuberance present inside (up to 0.9 mm long); claw ca 1 mm long. Right wing concealing the upper portion of the keel petals; claws 0.7-1 mm long; lamina obliquely obovate, 3.5-6.5 x 2.7-3.5 mm, notched at apex. Left wing claws 1-1.2 mm long; lamina obliquely obovate, 4-6.2 x 1.2-4 mm. Keel petals spirally incurved to left, 6-6.5 x 2.5-3.5 mm; horn-like pocket present (1.5-1.7 mm long) on the left side of keel petal. Stamens 9+1, included; staminal tube 4.5-5 mm long; free filament 8-9 mm long; anthers dorsifixed, 0.2-0.3 mm long. Pistil 1.5-1.8 cm long; ovary linear, 2.2-2.4 mm long, densely covered with long whitish hairs; style filiform, 1.2-1.3 cm long, ‘S’ shaped before stigma, beaked beyond stigma; beak 0.8-1 mm long, upwardly curved at apex. Pods ascending linear, cylindrical, 2-5 x 0.3-0.5 cm, straight or slightly curved, densely covered with brownish, 2-3 mm long spreading hairs, acute at apex. Seeds 4-10 per pod, broadly rectangular, 3-3.1 x 2-2.1 mm, brown, mottled with faint black patches, rounded or rectangular at both ends; seed coat porous with mesh-like reticulation; hilum well developed, rim-aril protruded, elliptic, 1.8-2 x 0.7-0.9 mm, whitish-brown. Germination epigeal; ecophylls petioles, simple and minutely pulvinous. Cleistogamous flowers: 2-5, whitish-yellow on leafless sub-aerial branches which produce on lower nodes of stem; pedicels 1-2 mm long; bracts lanceolate, 5-6 mm long, acute at apex, densely hairy; bracteoles 2, linear, 7-9 mm long, densely covered with 1-3 mm long bulbous based hairs. Calyx as in chasmogamous flowers. Standard petal symmetrical, broadly ovate, 4.5-5 x 5.5-6 mm, emarginate at apex, inside central protuberance absent; claws 0.3-0.5 mm long. Right wing petal slightly concealing the upper portion of the keel petal; claws 0.3-0.5 mm long; lamina obliquely ovate, 4.5-5 x 2-3 mm; auricle 0.1-0.2 mm long. Left wing petal spreading; claws 0.5-0.7 mm long; lamina ovate-elliptic, 4.9-5 x 2-2.7 mm, base oblique; auricle 0.3-0.5 mm long. Keel petals slightly curved, 4.8-5 x 1.5-2.5 mm. Stamens 9+1, dimorphic, out of 9 stamens in a bundle 4 short and 5 long; short stamens sterile with ca 1 mm long filaments, whereas long stamens fertile with ca 2 mm long filaments; staminal tube ca 1.5 mm long; free stamen sterile with ca 2 mm long filament; anthers dorsifixed 0.2-0.6 mm long. Pistil filiform, up to 6.5 mm long; ovary linear, 1.7-2 mm long, glabrescent or sparsely hairy; style filiform, 3-3.5 mm long, curved (not ‘S’ shaped), densely hairy before stigma with 0.4-0.6 mm long hairs, beaked beyond stigma; beak short, 0.3-0.5 mm long, straight, pointed at apex. Pods linear, cylindrical, straight, 2.5-4 x 0.3-0.4 cm, narrowed at both ends, sparsely hairy with short hairs (0.5 mm long), white hairs. Seeds 8-9 per pod, obliquely rounded, 3.5-4 x 3-3.5 mm, dark brown; seed coat foveolatewith mesh-like reticulation; hilum well developed, protruded, broadly elliptic, 2-2.2 x 0.4-0.7 mm, whitish. Germination epigeal; ecophylls petioles, simple and minutely pulvinous. (Figs 1, 2, 7​).

Vigna yadavii similis, ramis dimorphis, floribus cleistogamis vexillo sine processo carina sine marsupio corniformi, styli rostro applanato, seminum testa foveolata, hilo bene evoluto differt.

The specific epithet honors Prof AK Pandey, Department of Botany, Delhi University, New Delhi (India), in recognition of his valuable contribution to the taxonomy of flowering plants of India.

India, Maharashtra, Satara district, near Chalkewadi in Patan tahsil.

It is a twining annual herb, grows on lateritic gravelly soil on hill slopes amonggrasses and herbs at about 1200 m altitude above mean sea level in Satara district of Maharashtra, India. The species has adapted to the monsoon seasonality. It thrives in humid climate with heavy rainfall during growth season. The seed germination takes place with onset of monsoon rain in the first week of June and the plant completes its life cycle with formation of seeds when rains ceasein mid October. The common associates of the species are Carvia callosa (Nees) Bremek., Crotalaria nana Burm. f., Crotalaria vestita Baker, Cajanus lineatus (Wight & Arn.) Maesen, Eragrostis spp., Pseudarthria spp., Nogra dalzellii (Baker) Merr. and Themeda spp.

Interestingly, two types of shoots are observed in the species, one a normal aerial leafy shoot and the other subterranean (close to soil surface) leafless shoot producedatthe lower nodes of the stem. The later shoots produce cleistogamous flowers, which remain closed. They show differences in the structure of their floral parts as compared to chasmogamous flowers such as standard petal without central protuberance inside, keel petals without horn-like pocket, curved style and short style beak (0.3-0.5 mm long). (Figs 3, 4, 5, 6​). The floral parts of chasmogamous flowers roughly correspond to the floral parts of the species of Vigna sect. Ceratotropis while cleistogamous floral parts correspond to the species of V. sect. Aconitifoliae of the same subgenus. Thus, it shows a combination of characters of species of both sections. The new species shows morphological similarities with Vigna yadavii Gaikwad et al. and Vigna dalzelliana (Kuntze) Verdc. but differs in its dimorphic branches, foveolate seed coat and absence of standard protuberance and horn-like keel pocket in cleistogamous flowers. A comparative account between above mentioned three species is given in Table 1.