Epiphytic herbs. Roots terete, not branching, glabrous, smooth or papillose (O. philippinensis Ames). Stem elongate, patentascending to erect, leafy, rooting at base, sparsely branching, the branches well above base in O. micrantha. Leaves conduplicate, articulate, distichous, linear, almost semi-terete, apex obtuse; leaf-sheaths finely ribbed or transversely wrinkled. Inflorescences lateral, solitary or in pairs, racemose, 1–6-flowered. Flowers resupinate or not, 0.3–0.6 cm wide, opening simultaneously, quaquaversal, sepals and petals green with maroon markings or greenish yellow, labellum yellowish green with brownish side lobes or white with violet markings. Sepals entire, free, obtuse or acute. Petals narrower than sepals. Labellum spurred, trilobed, rigidly attached to column; spur conical to cylindrical, bilobed at apex. Column foot absent; anther cucullate, short-rostrate, pollinia two, angular-ovoid, stipe about as long as pollinia, linear.