Family Orchidaceae Subfamily Apostasioideae
Apostasioideae Garay in Bot. Mus. Leafl. 19: 86 (1960). Type species: Apostasia odorata Blume.
Small to large terrestrial herbs. Rhizome with scale leaves or rhizome absent. Roots usually partly aerial and stilt-like, penetrating the base of the lower leaves or rhizome-scales (where present) or both, usually pressed against the lower part of the stem or rhizome, terete, longitudinally grooved or ribbed; subterranean portion branched , sometimes with root hairs, in Apostasia with small swollen tuber-like thickenings. Stems erect or ascending, branched or simple, terete to irregularly angular or ribbed. Leaves spirally arranged, convolute, not articulate, linear, oblong to ovate-oblong, narrowly elliptic or ovate-elliptic, in Neuwiedia plicate; apex acuminate; glabrous or with scattered hairs; underside with prominent nerves; herbaceous to papyraceous. Inflorescences erect, terminal, simple or branched; rachis glabrous or hirsute; with peduncle; floral bracts leafy, persistent, glabrous or hirsute. Flowers resupinate or not, only slightly zygomorphic, small to medium size; pedicel and ovary cylindrical or ellipsoid, 3-angled to terete, not twisted, 3-celled, with axillary placentation. Sepals 3, free; median sepal very similar to the lateral ones; midrib forming a thick ridge terminating in a subulate cusp overtopping the incurved apical margin. Petals 2, free, sometimes attenuate towards the base; midrib forming a thick, fleshy, projecting keel on the outside separated from the underlying tissue by a constriction and terminating in a free subulate cusp overtopping the incurved apical margin. Lip very similar to the other petals but sometimes broader, without further ornamentation. Column straight to strongly curved , formed by the fusion of the lower portion of the style, the base of the filaments, and the staminode (in some species of Apostasia), smooth, glabrous; stamens 2 (Apostasia) or 3 (Neuwiedia), the filaments apically partly free from the style, the anthers with 2 equal or unequal thecae, 2-locular, dorsifix or sub-basifix, introrse; staminode (in some species of Apostasia) median, adnate to the style; pollen in monads, powdery; free style portion terete, cylindrical, fleshy; stigma terminal, slightly swollen, rounded or pyramid-shaped, sometimes 2- to 3-lobed, the apex flattened. Fruit 3-locular, thin- walled or rarely fleshy, disintegrating or (in one species) opening with three valves; seeds rather numerous, not dust-like, ovoid to elliptic, usually on a shorter or longer stalk, in Neuwiedia apically provided with a minute appendage, which (in 2 species) is very long or thick; testa in Apostasia dark brown when ripe, usually alveolate or reticulate, sticky when dry.
(after Wood 1999)