12. Cleisostoma williamsonii (H. G. Reichenbach) Garay, Bot. Mus. Leafl. 23: 176. 1972.
红花隔距兰 hong hua ge ju lan
Sarcanthus williamsonii H. G. Reichenbach, Gard. Chron. 1865: 674. 1865; Cleisostoma elongatum (Rolfe) Garay; C. hongkongense (Rolfe) Garay; Echioglossum williamsonii (H. G. Reichenbach) Szlachetko; S. elongatus Rolfe; S. hongkongensis Rolfe.
Plants often pendulous. Stems to 70 cm, rather slender, 3-4 mm in diam., branched or unbranched, many leaved, internodes 1-2.5 cm. Leaves straight or slightly arching, terete, usually 6-10 cm × 2-3 mm, obtuse. Inflorescence lateral, ascending, longer than leaves, usually branched, densely many flowered; floral bracts ovate-lanceolate, ca. 2 mm. Flowers opening widely, pink, lip deep purple-red; pedicel and ovary ca. 5 mm, slender. Dorsal sepal ovate-elliptic, cymbiform, ca. 2.2 × 1.5 mm, rounded; lateral sepals obliquely ovate-elliptic, ca. 2.5 × 1.5 mm, base adnate to column foot, obtuse. Petals oblong, ca. 2.2 × 1 mm, obtuse; lip lateral lobes erect, ligulate-oblong, obtuse, ± incurved; mid-lobe narrowly ovate-triangular, fleshy, adaxially with a ridge raised and triangular near spur entrance; spur globose, ca. 2 mm in diam., slightly laterally compressed, concave, interior inconspicuously septate, with a back wall callus; callus 3-lobed, T-shaped; lateral lobules nearly horn-shaped, slightly recurved; mid-lobule shallowly bilobed at base and densely papillate-hairy. Column ca. 2 mm; anther cap truncate, broadly emarginate; stipe broadly ovate-triangular or miter-shaped; viscidium nearly crescent-shaped. Fl. Apr-Jun. 2n = 38.
Epiphytic on tree trunks in forests, lithophytic on rocks along wooded valleys; 300-2200 m. Guangdong, Guangxi, SW Guizhou, Hainan, SE to W Yunnan [Bhutan, NE India, Indonesia, Malaysia, Myanmar, Thailand, Vietnam].