Greek oncos – swelling, tumour; an allusion to the warty calli on the labellum of many species.
Epiphytic, epilithic or terrestrial herbs, sympodial, with creeping rhizomes. Stems usually thickened into variously-shaped pseudobulbs, subtended by bracts, green. Leaves basal and/or apical, 1-4, fleshy or leathery, flat or cylindrical. Inflorescences usually basal racemes or panicles, erect to pendent. Flowers usually resupinate, few-many, small to large, variously coloured but often yellow or brown. Sepals similar, dorsal free, laterals free or variously fused. Petals similar to dorsal sepal or sometimes larger, free. Labellum entire or 3-lobed, fused to base of column, midlobe often 2-lobed, with fleshy calli. Column short, stout, winged or lobed on each side. Pollinia 2, waxy, with stipe.
About 750 species from N, C and S America.
The often yellow and brownish flowers with labellum midlobe often 2-lobed.
Garay & Stacy (1974).
Source: (2005). Orchidaceae. In: . Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.