Description from Flora of China
Callista binocularis (H. G. Reichenbach) Kuntze; C. gibsonii (Lindley) Kuntze; Dendrobium binoculare H. G. Reichenbach; D. fimbriatum Hooker var. gibsonii (Lindley) Finet; D. fuscatum Lindley.
Stems oblique or pendulous, cylindric, 35-100 cm, 7-8 mm in diam., rigid, upper part sometimes slightly curved, unbranched, with many nodes, internodes 2.4-3.4 cm, with longitudinal grooves, pale yellow when dry. Leaves oblong or sublanceolate, 10-15 × 2.5-3.5 cm, leathery, base with papery sheaths, apex acute. Inflorescence apical on old leafless stem, often pendulous, 15-20 cm, sparsely several to 10- or more flowered; peduncle 1-2 cm; rachis dark purple, often flexuous; basal sheaths 4 or 5, overlapping, tubular or cupular, basal ones ca. 3 mm, upper ones to 1 cm, papery; floral bracts lanceolate, concave, cymbiform, 5-7 mm, apex acute. Pedicel and ovary 2.5-3.5 cm. Flowers spreading, orange, disk with a rounded chestnut or deep purple blotch on each side, anther cap pale yellow. Dorsal sepal elliptic, 14-16 × 10-11(or more) mm, 7-veined, apex obtuse; lateral sepals oblong, 14-16 × 9-10(or more) mm, 7-veined, apex obtuse; mentum subglobose, ca. 4 mm. Petals subelliptic, 14-16 × 8-9(or more) mm, 5-veined, margin entire, apex obtuse; lip subreniform, ca. 15 × 17 mm, adaxially densely finely papillate, base clawed, margin shortly fimbriate, apex emarginate. Column ca. 3 mm, foot ca. 3 mm; anther cap nearly subglobose, glabrous, front margin slightly erose.
Epiphytic on tree trunks in open forests; 800-1000 m. Guangxi (Lingyun), S Yunnan [Bhutan, NE India, Myanmar, Nepal, N Thailand, Vietnam].