Volume 10 > Part 1 > Year 2009 > Page 32 > Dioscoreaceae > Dioscorea

8. Dioscorea collettii Hook.f.wfo-0000389963

Fl. Brit. Ind. 6: 290. 1892; Prain & Burkill, Ann. Roy. Bot. Gard. (Calcutta) 14(1): 39. 1936; Hô, Câyco Viêtnam 3, 2: 932. 1993; Ding & Gilbert in Fl. China 24: 282. 2000; Thapyai et al., Thai Forest Bull. (Bot.) 33: 214. 2005.— Dioscorea gracillima var. collettii (Hook.f.) Uline ex R.Knuth in Pflanzenr. 4, 43: 253. 1924. Fig. 15, 16; Plate VI.

Accepted Name : This is currently accepted.

Synonyms & Citations :

Description : Climber to 3 m. Rhizome richly and irregularly branched and lobed, approximately 5.5–16.5 by 0.8–2 cm, shallowly buried, periderm not hard and lacking rigid, spine-like roots. Indumentum present as papillae, 0.1–0.6 mm long, usually on veins of leaf lower surface, sometimes on young stems and inflorescence axes. Stems 2–5.6 mm in diam., twining to the left, annual, unarmed, terete, sometimes with shallow longitudinal ridges. Leaves simple, alternate, blade ovate to broadly ovate or deltoid, chartaceous, 7(–9)-veined, margins usually entire, sometimes with 3–5 shallow lobes, base widely cordate to subcordate, sometimes auriculate, apex acuminate; petioles (0.8–)3.2–9.5 cm long; cataphylls, lateral nodal organs and bulbils absent. Inflorescences pendent, axes angled, tepals fused at base, inserted on cup-shaped torus, free above; male inflorescences usually simple, rarely compound, compound inflorescences 1(–2) per axil, simple/partial inflorescences 1–2(–3) per axil, spicate, with apparently sessile cymules of 1–3 flowers, peduncles 0.3–2 cm long, axes 3–18 cm long; female inflorescences spicate, 1 per axil. Male flowers with tepals oblong, outer 1.1–1.5 by 1.1–1.2 mm, inner 1.2–1.8 by 0.7–1 mm, oblong, stamens 3, filaments filiform, connective bifid to form two divergent arms, anthers ovate-oblong, dorsifixed at the arm tips; staminodes 3, 0.25–0.4 mm long, filiform. Female flowers as in Fig. 16B–G. Capsules as in Fig. 16H, Pl. 6G, 20–23 by 20–25 mm. Seeds 3.5 by 4 by 5–6 mm, ovoid-lenticular, wings 12.5–15.5 by 9.5–11 mm, extending all around seed margin.

Thailand : NORTHERN: Chiang Mai (Doi Chiang Dao).

Distribution : India, Burma (type), China.

Ecology : Open areas of hill evergreen forests, 1,450–1,500 m alt. Flowering: June August; fruiting: September–November.

Conservation Status: IUCN red list category LC (IUCN 2001); see Thapyai et al. (2005a). While it is rare in Thailand, on a regional level Dioscorea collettii appears to be relatively abundant and occurs over a wide geographical area.

Notes: This species is easily recognised by the presence of papillae on the veins of the lower surface of the leaf blade. Thai material appears to belong to var. collettii sensu Ding & Gilbert (2000), which also occurs in Burma, while Dioscorea collettii var. hypoglauca (Palibin) C.T.Ting et al. has not been collected south of Hunan and Guangdong provinces in south central China. The type of D. tashiroi Hayata (Taiwan (Formosa), Kotosho, Toshiro s.n.) has not been located and the synonymy follows Prain & Burkill (1936) and Ding & Gilbert (2000).