Subfamily Epidendroideae Lindl. Coll. Bot., App. 1826.
Perennial, terrestrial, epiphytic, or lithophytic herbs or rarely scrambling climbers, either sympodial or monopodial, with short to long rhizomes; plants rarely heteromycotrophic, achlorophyllous and with leaves absent or reduced to scales. Roots slender and wiry to stout and shoelacelike, rarely coralloid, with a 1- to several-layered velamen, smooth to warty, terete to dorsiventrally flattened; aerial roots adventitious.
Stems usually leafy, but leaves often reduced in number and rarely reduced to bractlike scales, 1 or more internodes at base often swollen to form a pseudobulb. Leaves entire, alternate or occasionally opposite, often distichous, frequently fleshy or leathery, rarely terete or canaliculate, with a basal sheath, sometimes articulated at base.
Inflorescences erect to pendulous, spicate, racemose, or paniculate, 1- to many flowered, basal, lateral, or terminal. Flowers small to large, often quite showy, usually pedicellate, mostly resupinate, glabrous to hairy; ovary inferior, 1-locular. Sepals usually free but sometimes variously adnate, dorsal often dissimilar to laterals, laterals sometimes adnate to column foot to form a saccate, conic or spurlike mentum. Petals free or rarely partly adnate to sepals, similar or not to sepals, often showy; lip entire, variously lobed, or 2- or 3-partite, ornamented or not with calli, ridges, hair cushions, or crests, with or without a basal spur or nectary, margins entire to laciniate.
Column short to long, with or without a basal foot, occasionally winged or with lobes or arms at apex or ventrally; anther 1, ± terminal on column, caplike, attached to column apex by a short filament; pollen in tetrads, usually in discrete pollinia; pollinia mealy or waxy, 2, 4, 6, or 8, sessile on viscidium or attached by stipe or stipes to 1 or 2 sticky viscidia; stigma 3-lobed, concave, usually viscous; rostellum usually transverse, less commonly elongate and 1-3-lobed. Fruit a capsule, opening laterally by 3 or 6 slits. Seeds fusiform to discoid, numerous, dustlike, lacking endosperm, sometimes markedly winged; elaters often present.
About 600 genera and 18,000 species in 16 tribes: cosmopolitan.