Orchidaceae Juss., Gen. Pl. [Jussieu] (1789) 64; nom. cons.
Sympodial or less often monopodial, perennial epiphytes, less often terrestrials, or occasionally lithophytes or climbers, sometimes saprophytes; woody or herbaceous, Roots adventitious, when dry usually whitish, often aerial; with (a) layer(s) of empty water-absorbing cells (velamen) in epiphytes and in some terrestrials; sometimes roots green and assimilating; infected by mycorrhizal fungi (also in the basal part of the plant). Rhizomes often present, less often tubers, or rootstocks. Stems cane-like or a pseudobulb, almost always with 1 or more leaves, with 1 or more internodes, glabrous or sometimes hairy. Leaves duplicate or convolute, alternate, often distichous, or occasionally opposite or spirally arranged, usually entire, rarely palmate or lobed, usually dorsoventrally flattened, less often bilaterally flattened, sometimes terete or canaliculate, sometimes the lower ones or all reduced to scale leaves; texture membranous to coriaceous; glabrous, sometimes hairy; venation parallel, sometimes curved; leaf sheath often present, often articulate with the blade; base of the blade sometimes petiole-like. Inflorescences lateral or terminal on the stem, or from the rhizome, racemose, paniculate or spicate, 1- to many-flowered. Flowers bisexual or rarely unisexual, rarely polymorphic, small to large; zygomorphic but occasionally almost actinomorphic, distichous or subumbellate, erect to pendent, showy or not; with pedicel, rarely sessile, usually tuned around 180° (resupinate), sometimes not resupinate, or turned around 360°. or turned backwards 180°. Pedicel and ovary not separated by a node; ovary inferior, 1-locular with parietal placentation or rarely 3-locular with axillary placentation, smooth or with ribs or keels. Sepals 3, usually free, occasionally connate; median sepal zygomorphic, its margin entire or variously ornamented; lateral sepals in most cases asymmetric with the facing sides wider, their margin entire or variously ornamented, sometimes attached on a column foot forming a saccate, conical or spur-like mentum. Petals 3, free; median petal usually differently shaped, named lip or labellum; sometimes the lateral petals adnate to the sepals or rarely inserted on the basal part of the column. Lip not lobed or often 3-lobed, with or without calli, ridges, hair cushions, or keels, with or without a spur or nectary; margins entire or variously ornamented. Column short to long, composed by fusion of a style and (a) filament(s), with or without a column foot, with or without wings or lobes or arms; anther 1 (Epidendroideae Orchidoideae and Vanilloideae), 2 (Cypripedioideae 2) or 2 or 3 (Apostasioideae), terminal or lateral, when 1 erect, leaning backwards or bent forwards, often cap-like, opening by longitudinal slits; pollen not cohering, mealy or paste- like, not united in pollinia (Apostasioideae, Cypripedioideae and Vanilloideae) , or pollen in monads or tetrads , cohering into specifically shaped bodies named pollinia (Epidendroideae Orchidoideae); pollinia 2, 4, 6 or 8, mealy, waxy or horny, soft to hard, sectile or not, separate and then either or not attached to caudicles, or attached to 1 or 2 stipes, tegulas or hamuli to 1 or 2 sticky viscidia forming 1 or 2 pollinaria; stigma 3-lobed, on the front of the column below the anther, the lobes often not pronounced, the midlobe often modified into a rostellum, the other lobes either sunken or with a raised margin. Fruit a capsule, composed of 3 valves and 3 (usually narrow) jugae, usually opening by separation of the jugae from the valvae, rarely berry-like (Apostasioideae); seeds numerous, dust-like, lacking endosperm, sometimes markedly winged; rarely with limited number of seeds with a hard seed coat (Apostasioideae).
(after Cribb 1999)