Dendrobium longlingense Q.Xu, Y.B.Luo & Z.J.Liu, 2014

Xu, Qing, Zhang, Guo-Qiang, Liu, Zhong-Jian & Luo, Yi-Bo, 2014, Two new species of Dendrobium (Orchidaceae: Epidendroideae) from China: evidence from morphology and DNA, Phytotaxa 174 (3), pp. 129-143 : 140-142

Dendrobium longlingense Q.Xu, Y.B.Luo & Z.J.Liu , sp. nov. (įä石ª; Figs. 6 , 7 )

Type:— China. Yunnan (云南): Longling (įä), epiphytic on tree trunks in forests; 1650 m, 10 February 2014, Liu 7454 (holotype: NOCC!) .

Diagnosis: this new species is similar to Dendrobium longicornu , but differs in having: the abaxial surface of leaves and leaf sheaths covered by dense black hairs; subterminal racemes from leafless stems; pale yellow sepals and petals; a golden yellow lip; slightly curved not straight spur; subflabellate lip with the midlobe apex shallowly bilobed with a sharp tooth; disk with 1 thick, fleshy longitudinal ridge extending from base to apex of midlobe.

Epiphytic herbs. Stems clustered, cylindric, 7–20 cm long, 4–7 mm in diameter, unbranched, internodes 5–30 mm long. Leaf obovate-elliptic or narrowly lanceolate, 2.5–5.5 × 1.1–1.4 cm, apex unequally bilobed, abaxial surface with short, black hairs, leaf sheaths densely black hirsute. Racemes subterminal, from leafless stems, 2–3-flowered; peduncle 3–4 mm long; floral bracts ovate-lanceolate, 6–7 mm long, abaxially dark brown, hairy. Pedicel and ovary nearly cylindric, 2.4–2.7 cm long. Flowers spreading; sepals and petals pale yellow, lip golden yellow, column white. Dorsal sepal ovate-elliptic, 14.0–15.0 × 6.0– 7.5 mm, apex acute, midvein slightly keeled abaxially; lateral sepals nearly ovate-triangular, 15–17 × 8–10 mm, apex acute, midvein slightly keeled abaxially; mentum narrow, long, angulate, slightly curved, forming a spur, 1.8–1.9 cm long. Petals oblong, 15–17 × 4–5 mm, apex acute; lip subflabellate, 20–21 × 24–25 mm, apex trilobed; lateral lobes obovate, 19–20 × 10–11 mm, nearly erect, embracing column; midlobe subrounded, 4–5 × 6–7 mm, apex shallowly bilobed with a sharp tooth, margin undulate and toothed; disk with 1 thick, fleshy longitudinal ridge, extending from base to apex of midlobe. Column 3–4 mm long, teeth triangular; pollinia 4 in 2 pairs, oval.

Flowering period: — February to April.

Distribution and habitat: — Dendrobium longlingense is epiphytic on tree trunks in forests at 1650 m in Longling, Yunnan Province, China.

Etymology: —The species epithet refers to the locality where this new species was first found.

Conservation status: —Using the World Conservation Union Red List Categories and Criteria ( IUCN, 2001), D. longlingense should be treated as critically endangered.

Species recognition: — Dendrobium longlingense is distinct among species in the genus because it has dense black hairs on leaf abxial surface and leaf sheaths, subterminal inflorescences arising from leafless stems, and a golden yellow lip slightly curved to form spur . The lip is subflabellate with a sharp tooth at the apex of midlobe and a disk with one thick, fleshy longitudinal ridge. It is morphologically similar to D. longicornu , but can be easily distinguished from the latter, which has blackish brown rigid hairs on both leaf surfaces and leaf sheaths and subterminal inflorescences on leafy stems. The lip is subobovate or rhombic. The central part of the disk is orange with 3 or 4 keeled longitudinal ridges. The mentum is straight and forms a spur.

Figures

FIGURE 6. Dendrobium longlingense Q.Xu, Y.B.Luo & Z.J.Liu. A. Flowering plant. B. Flower, front view. C. Flower, side view. D. Dorsal sepal, petal, lateral sepal and lip. E. Column. F. Pollinarium.

FIGURE 7. Dendrobium longlingense. A. Flowering plant. B. Flower, front view. C. Flower, side view. D. Column. E. Pollinarium. F. A flower of D. longcornu.