景洪石斛 jing hong shi hu

Ceraia exilis (Schlechter) M. A. Clements.

Stems erect, upper part branched, cylindric, to 50 cm, slender, ca. 3 mm in diam., 2 or 3 internodes above base dilated and fusiform; dilated portion of stems ca. 4.5 cm, ca. 8 mm in diam., fleshy, with 4 ribs, with pale white membranous sheaths when young, reddish brown and glossy when old. Leaves often alternate on upper part of branches, erect, terete, 2.5-6 × 1.5-2.5(or more) cm, base with leathery sheaths, apex acute. Inflorescence axillary on leafy older stems, 1-flowered, up to 4 flowers open at once per stem; floral bracts ovate, ca. 2 mm. Pedicel and ovary ca. 1 cm, slender. Flowers spreading, white, inner surface of lip lateral lobes with a few pale purple spots, disk yellow. Dorsal sepal sublanceolate, ca. 17 × 2.5 mm, 5-veined, long acuminate; lateral sepals similar to and ca. as large as dorsal sepal; mentum rigid, ca. 1 cm, acute. Petals similar to sepals, ca. 17 × 1.5 mm, 3-veined; lip cuneate at base, 3-lobed above middle; lateral lobes obliquely subovate-triangular, front margin undulate, apex obtuse; mid-lobe narrowly oblong, margin undulate, apex acute; disk sparsely villous, with 3 thick and stout keeled ridges from base to apex. Column ca. 2 mm, foot with a basal callus; anther cap conic. Capsule fusiform, ca. 4 × 0.6 cm.

Epiphytic on tree trunks in open forests; 600-800 m. S Yunnan (Jinghong, Mengla) [Thailand, Vietnam].