Epiphytic or lithophytic herbs. Roots flattened, borne from lower nodes. Stem elongate, erect or climbing, often branched at base giving a tufted habit, some with a single shoot, terete, usually stiff, enclosed in leaf-bases. Leaves many, well-spaced, linear, terete, distichous, quaquaversal or secund, articulated to a tubular sheathing base. Inflorescence lateral, erect or ascending, racemose, subsessile, fewer than 10-flowered, with few to several flowers opening simultaneously, sometimes reduced to a solitary flower; peduncle and rachis attenuate, rachis congested. Flowers resupinate, usually greenish with a maroon labellum, continuing to increase in size for some days after they open, long lasting. Sepals and petals free, similar or petals longer and narrower, spreading, lateral sepals often cymbiform and dorsally carinate or narrowly winged toward apex. Labellum firmly adnate to base of column, spur absent, pendent, flat, often distinctly divided by a transverse, curved furrow into a narrow basal hypochile and a broader apical epichile of different thickness and texture, hypochile often concave, base sometimes with lateral lobes embracing column, epichile often extending forward, adaxial surface often longitudinally wrinkled, grooved or tuberculaterugose. Column straight, semi-cylindrical, column foot absent, clinandrium shallowly excavate; anther cap terminal, operculate, pollinia two, waxy, globular, solid, with a short slit, caudicles absent, attached by a short and broad stipe to a single short, broad viscidium; rostellum apex subtruncate, entire or slightly emarginate; stigma transverse. Ovary triangular in cross-section.