Dendrobium trigonopus Rchb.

19. Dendrobium trigonopus Rchb. View in CoL f.

The Gardeners’ Chronicle, ser. 3, 2: 682 (1887). — Gagnep., Flore générale de l’Indo-Chine 6 (2): 238 (1933). — Seidenf., Opera Botanica 83: 109, fig. 65, table 14c (1985); 114: 210 (1992). — Newman et al., A Checklist for the Vascular Plants of Lao: 265 (2007). — Schuiteman et al., Nordic Journal of Botany 26: 288 (2008). — Zhu Guanghua et al., Flora of China 25: 391 (2009). — Aver., Turczaninowia 8 (1): 62, table 1e (2005).

TYPUS. — Myanmar. Birmah, Messrs. Hugh Low & Co., IV.1887

( type location unknown). HABITAT, PHENOLOGY AND CONSERVATION STATUS. — Epiphyte

on tall trees in primary evergreen broad-leaved forest on granite, shale and rocky limestone, particularly on steep rocky slopes and on mountain tops. 800-1800 m. Fl. (February) March-May, October. Rare. Expected IUCN Red List status – EN.

DISTRIBUTION. — Laos ( Khammouan, Vientiane), Vietnam ( Dien Bien, Lam Dong, Son La). Myanmar , S. China , N. Thailand .

MATERIAL EXAMINED. — Laos. Khammouan, M.Newman et al., s.n. ( NUOL cult. OL 645), B.Svengsuksa et al., s.n. ( NUOL cult. OL 1300, OL 821); Vientiane, A.D.Kerr 0330 ( K); Vientiane, N.Soulivong s.n., ( NUOL cult. OL 309); Vientiane, Phu Khao Khouai, Rendon 118 ( C), A.D.Kerr 2479, 2481 ( C); Xiangkhouang, Kham, Huad village, LA-VN 1095 ( FOF, HNL, LE).

Vietnam. Dien Bien, Na U, CPC 2427 View Materials ( LE, LE photo) ; Dien Bien, sine loc., L. Averyanov s.n., IV.2011 ( LE photo) ; Lam Dong, Dalat area , L.Averyanov s.n., anno 2004 ( LE photo) ; Lam Dong, Dalat area, L. Averyanov s.n., X.2005 ( LE photo) ; Son La prov., Son La city area, P. K. Loc P-10701 ( LE, LE photo) ; Son La, Son La city area, Chieng Co , CPC 1141 View Materials a ( LE, LE photo); NW Vietnam, sine loc., HAL 12851 K ( LE photo) .

DESCRIPTION

Stems fusiform to clavate, 5-15(20) cm, 1-1.8 cm in diameter, with (4)5-10 nodes. Leaves narrowly ovate to oblong lanceolate, 5-8(10) cm long, (1)1.5-2(2.5) cm wide. Inflorescences 1-3(4), each with 1-3 flowers; floral bracts ovate, acute, 4-8 mm long. Pedicel and ovary yellowish green, 2-5 cm long, ovary trigonous in section. Flowers sweet honey fragrant, slightly nodding, widely opening, 2.5-3.5(4) cm across, yellow, lip disc tinged with pale green. Sepals and petals subsimilar, triangular ovate, acute to shortly acuminate, (1.5)2-2.5(3) cm long, 0.7-1 cm wide; sepals dorsally keeled; petals little wider. Lip very rigid, densely verruculose, nearly parallel to column, denticulate along margin, shortly clawed, suborbicular, (1.5) 1.8-2.5 cm long and wide, 3-lobe; side lobes broadly obovate to obscurely quadrate, apex rounded to truncate; median lobe triangular to reniform, obtuse, orbicular to slightly emarginate. Mentum subglobose, 3-5 mm long and wide. Column pale yellow, 5-6 mm tall, anther cap conical, glabrous, 2-3 mm tall and wide ( Fig. 4I View FIG ).

REMARK

Records of this species for southern Vietnam ( Lam Dong) are based on cultivated plants probably originated from Dalat City area. These records need confirmation by further field investigations. Molecular studies place this species outside of section Formosae ( Sathapattayanon 2008).