genus of more than 300 species of tropical American orchids, family Orchidaceae, that grow on other plants or on soil at high altitudes. Some species are less than 5 cm (2 inches) tall, but others may grow to nearly a metre (about 3 feet).

Pseudobulbs (bulblike stems) vary in position, shape, and size, depending on the species, but usually are flattened and spaced along a creeping underground stem. The leaves are thick and leathery. Most species bear a single flower or a cluster of several flowers.