Dendrobium williamsonii Day & Rchb.

Averyanov, Leonid V., Ponert, Jan, Nguyen, Phi Tam, Duy, Nong Van, Khang, Nguyen Sinh & Nguyen, Van Canh, 2016, A survey of Dendrobium Sw. sect. Formosae (Benth. & Hook. f.) Hook. f. in Cambodia, Laos and Vietnam, Adansonia 38 (2), pp. 199-217 : 212

12. Dendrobium williamsonii Day & Rchb. f.

The Gardeners’ Chronicle and Agricultural Gazette 1869: 78 (1869). — Hook.f., Annals of the Royal Botanic Garden, Calcutta 5, table 9 (1895). — Hemsley, Botanical Magazine 130: table 7974 (1904). — Gagnep., Flore générale de l’Indo-Chine 6 (2): 230 (1933). — Seidenf., Opera Botanica 83: 121, fig. 75b, 77, table 16b (1985); 114: 217, fig. 138 (1992). — Aver., Identification Guide to Vietnamese Orchids: 182 (1994). — P.H.Ho, An Illustrated Flora of Vietnam 3: 828, fig. 11065 (2000). — Aver. & Averyanova, Updated Checklist of the Orchids of Vietnam: 31 (2003). — Zhu Guanghua et al., Flora of China 25: 393 (2009).

TYPUS. — NE India. Assam, Williamson s.n., Herb. Reichenbach, 32461 ” (holo-, W?).

HABITAT, PHENOLOGY AND CONSERVATION STATUS. — Epiphyte on old trees in primary and secondary evergreen and semideciduous broadleaved, mixed and coniferous mountain forests on shale, sandstone, granite and rocky limestone, commonly on steep rocky slopes and on mountain tops in wind-formed thickets. (600) 900- 1500 m. Fl.: March-May. Locally common. Expected IUCN Red List status – EN.

DISTRIBUTION. — Laos (Phongsali), Vietnam (Cao Bang, Da Nang, Dien Bien, Ha Giang, Lao Cai, Quang Binh, Quang Tri, Son La, Vinh Phuc). NE. India, Myanmar , S. China .

MATERIAL EXAMINED. — Laos. Phongsali, Muong May, CPC 2429 ( LE photo).

Vietnam. Cao Bang, Nguyen Binh, Ca Thanh, CBL 1311 ( HN, LE, LE photo, MO) ; Da Nang, Bana , Tourane, Poilane 7150 ( P [ P00408316 ]) ; Dien Bien, Muong Cha, Mua Ngai, L . Averyanov CPC 1088 a ( LE), 1088c ( LE, LE photo); Ha Giang, Meo Vac , Sung Chang, CBL 1852 ( HN, LE, MO) ; Ha Giang, Quan Ba, Bat Dai Son mt. , HAL 11854 ( HN, LE), T. V . Thao & N. S . Khang VT 014 ( HN), DKH 5225 ( HN, LE, MO) ; Ha Giang, Quan Ba , Can Ty, HAL 1456 ( HN, LE photo), HAL 1549 ( HN), P. V . The , CPC 144 ( LE photo) ; Ha Giang, Quang Ba , Sin Suoi Ho, DKH 4800 ( HN, LE, MO) ; Lao Cai, Sa Pa, L . Averyanov s.n., 26.IV.2008 ( LE photo) ; Quang Binh, Bo Trach, Phong Nha - Ke Bang, HAL 6227 ( HN) ; Quang Binh, Minh Hoa, Dan Hoa, d-EXSICCATES OF VIETNAMESE FLORA 138 / HAL 11716 ; Quang Binh, Minh Hoa, Dan Hoa, Giang Man mt. , HAL 11716 ( HN, LE, LE photo, MO) ; Quang Binh, Minh Hoa, Phong Nha - Ke Bang, HAL 5860 ( HN) ; Quang Tri, Huong Hoa, Huong Phung, d-EXSICCATES OF VIETNAMESE FLORA 73 /HLF6298; Quang Tri, Huong Hoa , Huong Phung, Sa Mui pass, HLF 6298 ( HN, LE, LE photo) ; Son La, sine loc., HAL 12851 ( P. K. Loc - photo) ; Vinh Phuc, Tam Dao, A . Petrov s.n. anno 2012 ( LE) .

DESCRIPTION

Stems erect, narrowly fusiform, of many nodes, to 10-25(30) cm long and 0.5-1 cm in diameter. Leaves narrowly ovate to oblong lanceolate, 5-10 cm long, 1-2.5 cm wide. Inflorescences 1-3, each with 1-3 flowers; floral bracts ovate, acute, 4-5 mm long. Pedicel and ovary white, to 2-3 cm long; ovary conical, without distinct keels. Flowers widely opening, light pale yellowish to almost white, 3.5-4.5 cm across. Sepals and petals subequal, triangular narrowly ovate, acute to acuminate, 2-3 cm long, 0.6-1 cm wide; lateral sepals dorsally carinate, oblique, forming conical., spur-like mentum 1.4-1.82 cm long. Lip pale yellowish to almost white, broadly obovate, 2-3.5 cm long, 1.5-2.5 cm wide, 3-lobed, side lobes half circular, erect, embracing column; median lobe half circular to broadly obovate, finely irregularly denticulate and undulate along margin, acute to shortly apiculate; disc and median lobe red to orange, sparsely long ciliate or fimbriate along veins, sometimes indistinctly carinate. Column white to pale reddish, 5-7 mm tall; anther cap white, broadly conic ( Fig. 3 B-D).

Figures

FIG. 3. — A, Dendrobium multilineatum Kerr (LA-VN 256); B-D, Dendrobium williamsonii Day & Rchb.f. (CPC 24290); E, F, D. cariniferum: Rchb.f.; E, VH 2256a; F, HLF 5500a; G, H, D. longicornu Lindl. (CPC 5378); I, D. chapaense Aver. (N.A.Duc et al., HL 131). Photos: A, N. S. Khang; B-H, L. Averyanov; I, N. A. Duc.