Genus of over 450 species of evergreen, terrestrial, epiphytic, or lithophytic orchids found in Mexico, Central America, South America, and thr West Indies. The genus is characterised by the presence of one or two leafed pseudobulbs with a single internode that is normally subtended by distichous leaflike sheaths which give rise to the inflorescense. The flowers are spurless and often have wings on either side of the stigma and it has a footless column that has the basal part of the lip attached. It has two hard pollina attached to a stipe connected to a viscidium. The flowers are typically yellow, with prominent lips. and are produced in short or tall racemes or panicles from the bases of the plants.