Small to large terrestrial, lithophytic or epiphytic herbs with elongate, fibrous roots arising from a short to elongate rhizome. Erect shoots leafy, clustered or less frequently well spaced, glabrous, the base enclosed by two to four sheathing sterile bracts, three- to several-leaved above. Leaves several, coriaceous, conduplicate, spreading or suberect, ligulate, elliptic, or oblong, obtuse to acute, often tridenticulate at apex, mid- to dark green on upper surface, lighter green below, glabrous, ciliate or not on the margins. Inflorescence terminal, occasionally branching, few- to many-flowered; rachis terete, hairy, glandular or glabrous; bracts conduplicate, elliptic, lanceolate, ovate or oblong, green, sometimes spotted or flushed or striped with purple, ciliate or not. Flowers deciduous, usually showy, concolorous or not, vernation imbricate; pedicel obscure to short; ovary trilocular, three-ribbed, glabrous or hairy. Dorsal sepal erect to hooded over lip, ovate, lanceolate, obovate or elliptic, obtuse, acute or acuminate, glabrous or pubescent on the outer surface, sometimes pubescent within at base, ciliate or not. Lateral sepals usually fused to form a concave synsepal that is more or less similar to the dorsal sepal, sometimes keeled on outer surface. Petals free, spreading or pendent, flat, reflexed or spiraling, elliptic, ovate, lanceolate, linear-lanceolate, linear or oblanceolate, rounded, obtuse, acute or acuminate at apex, often pubescent in basal half within, usually ciliate. Lip deeply pouched and inflated, slipper-shaped or urn-shaped, with more or less pronounced incurved side lobes, rarely petaloid, hairy within especially on lower surface, glabrous or hairy on outer surface; front margin incurved or not. Column short, stalked, porrect; anthers two, bilocular, borne on short obtuse to acute filaments; pollen powdery or viscid; staminode terminal on column, sessile or shortly stalked, transversely reniform, oblong, ovate, obcordate or linear, flat, convex or longitudinally conduplicate, glabrous to papillose or finely pubescent, ciliate or not; stigma stalked, dependent, tripartite, more or less papillose. Capsule erect to pendent, three-ribbed, cylindrical to almost ellipsoidal. (PC).