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Description


Twining dioecious herbs, tubers variable in shape, colour  and, depth in ground. Axillary bulbils present or absent. Leaves mostly alternate, sometimes opposite, petiolate, simple or palmately compound, with 3-7 leaflets, nerves palmate in simple leaves and pinnate in  leaflets. Male inflorescence : axillary, spicate, racemose or rarely cymose, flowers small, green or rosaceous or whitish, stamens 6, sometimes inner 3 forming staminodes. Female inflorescence : axillary, spicate, 3.5-10.0 cm long,  few flowered, staminodes present or absent. Fruit a capsule, 3-winged, dehiscent. Seeds with a membranous wing.

Key to the species

Serial Key Reference
1a. Stems twining to the left 2
1b Stems twining to the right 7
2a. Leaves simple 3
2b. Leaves 3-5 foliate 5
3a. Capsule wings 2.5 times as long as wide Dioscorea prazeri
3b. Capsule wings much less than this dimension 4
4a. Plants unarmed; stems glabrous; seeds winged at base only Dioscorea bulbifera
4b. Plants armed; stems pubescent with T-shaped hairs; seeds winged around Dioscorea esculenta
5a. Fertile stamens 6 Dioscorea hispida
5b. Fertile stamens 3 6
6a. Stems tomentose; flowers sessile; leaves usually 3-foliate, rarely 5-foliate Dioscorea tomentosa
6b. Stems glabrous, flowers pediculate; leaves 3-5 foliate Dioscorea pentaphylla
7a. Stems densely pubescent Dioscorea pubera
7b. Stems glabrous 8
8a. Plants armed 9
8b. Plants unarmed 11
9a. Stems winged or angled Dioscorea alata
9b. Stems terete 10
10a. Leaves up to 10 cm long; capsules green, without brown flecks Dioscorea glabra
10b. Leaves more than 10 cm long; capsules stramineous, with brown flecks Dioscorea wallichii
11a. Stems 6-angled Dioscorea hamiltonii
11b. Stems terete 12
12a. Bulbils present and black at maturity Dioscorea melanophyma
12b. Bulbils either absent or when present not black at maturity 13
13a. Bulbils either absent or small 14
13b. Bulbils present, not black at maturity Dioscorea kamoonensis
14a. Leaves coriaceous Dioscorea spicata
14b. Leaves not coriaceous 15
15a. Leaves usually ovate, cordate at base Dioscorea belophylla
15b. Leaves otherwise, obtuse or rounded at base Dioscorea oppositifolia