Herbs, terrestrial, epiphytic, or saprophytic; true bulbs lacking; leaves undivided, often fleshy or leathery; stems leafy or scapose, often thickened at base into pseudobulbs bearing aerial roots; flowers perfect (rarely unisexual), very irregular; perianth parts 6, all petaloid; stamens 1-2, adnate to the pistil; pollen granular or more commonly agglutinated into waxy or mealy masses (pol-linia), sometimes the pollinium with a caudicle; ovary inferior, 1-celled (very rarely 3-celled), often produced at the apex into a column; stigmas 3, often only 2 functional, the third transformed into a small growth (the rostellum) lying between the anther and the stigmas; part of the rostellum is sometimes modified into viscidia (disks to which the pollinia are attached). Fruit usually a capsule, opening laterally by slits. Seeds very numerous, minute, lacking endosperm, the embryo not differentiated. A large, cosmopolitan family of perhaps 600 genera and 20,000 species.