Dioecious epiphyte, often on rotting wood; pseudobulbs elongate, +/- cylindrical, tapering gradually toward apex. Leaves several, scattered along stem, plicate, deciduous, the bases persistent, imbricating. Racemes arching, ca 30 cm long, produced from near base to middle of pseudobulb (often leafless when in flower); staminate and pistillate flowers similar; sepals and petals subequal, spreading, linear-lanceolate, acuminate, to 5 cm long, greenish to yellowish-brown to cream-colored; lip elliptic- to rhombic-ovate, with a short claw, the lateral margins often strongly recurved; column twisted to one side, pointed, with a slender apical bristle. Fruits not seen. Croat 7794. Reported by R. Dressler to be distinct from M. colossus Reichb.f., with which it was included in synonymy in the Flora of Panama (Allen, 1949). Mormodes colossus occurs in western Panama and Costa Rica and can be distinguished from M. powellii by having a much wider lip. The species is pollinated by the bee Euglossa tridentata (Dressler,1968a).