藏南石斛 zang nan shi hu

Callista alpestris Kuntze; Dendrobium alpestre Royle (1839), not Swartz (1799); D. pusillum D. Don (1825), not Kunth (1815); D. roylei A. D. Hawkes & A. H. Heller.

Stems erect or ascending, to 10 cm, becoming narrower from base, fleshy, current ones enclosed in leaf sheaths, with several nodes, internodes ca. 1 cm. Leaves distichous along whole stem, narrowly oblong, 5-6 cm(or more) × 3.5-4.5 mm, thinly leathery, base dilated into gibbous sheaths, apex acute and unequally slightly bilobed; leaf sheaths loosely embracing stem, lowermost largest, uppermost smaller, sheath mouth obliquely truncate. Inflorescences 1-4, subterminal or arising from upper part of current year’s leafy stems, suberect or nodding, 2.5-5 cm, several flowered; floral bracts narrowly ovate, 2-3 mm, acute. Pedicel and ovary ca. 5 mm, slender. Flowers spreading, white, lateral lobes of lip with purplish red stripes, disk white with purplish red stripes, column foot with purplish red spots. Dorsal sepal narrowly oblong, (5-)7-9 × 1.5-1.8(or more) mm, 3-veined, acuminate; lateral sepals falcate-lanceolate, 7-9 × ca. 3.5 mm, 3-veined, base oblique, abruptly contracted above middle and acute; mentum broadly conic. Petals narrowly oblong, 6-8 × ca. 1.8 mm, 1-3-veined, acuminate; lip subelliptic, 5.5-6.5 × 3.5-4.5(or more) mm, shortly clawed, slightly crispate at middle, 3-lobed above middle; lateral lobes erect, margin comb-shaped, apex attenuate and sharply dentate; mid-lobe ovate-triangular, margin cristate-corrugate, acute, reflexed; disk central part with 2 or 3 lamellate ridged projections, ridges thickly fleshy, extending from base of lip to base of mid-lobe, apex slightly enlarged. Column ca. 3 mm, middle part stout, to 1 mm wide, upper part without conspicuous teeth, foot ca. 5 mm, margin densely finely papillate; anther cap subglobose, front margin slightly dentate.

Lithophytic on rocks in mountain valleys; 1700-2200 m. SW Guangxi (Napo), S Xizang (Gyirong, Nyalam) [N India, Laos, Nepal, N Thailand, N Vietnam].

Material of this species has been named as Dendrobium eriiflorum Griffith (Orchids China, 155. 1998).