Greek bi – two; frenum – a strap; an allusion to the paired strap-like stipes joining the pollinia to the viscidium.
Epiphytic, epilithic or terrestrial herbs, sympodial, with long creeping simple or branched rhizomes. Stems thickened into ovoid to conical pseudobulbs, somewhat compressed, well spaced, glossy green or yellow, often with an apical black collar. Leaves apical, solitary, leathery, shortly stalked. Inflorescences basal racemes, short, erect or arching. Flowers resupinate, 1-5, large, showy, fragrant, variously coloured. Sepals similar, dorsal free, laterals joined to column foot producing a short spur, spreading. Petals smaller than sepals, free. Labellum 3-lobed, hinged, side lobes embracing column, tip curved under. Column long, 2-winged at tip, with a short foot. Pollinia 4, in 2 pairs, with 2 stipes.
About 16 species from tropical S America.
Well spaced glossy green or yellow pseudobulbs often with a black apical collar; lateral sepals joined to column foot producing a short spur.
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.