Greek zygon – yoke; petalon – petal or sepal; the thickened callus at the base of the labellum appears to pull together or yoke the floral segments.
Epiphytic, epilithic or terrestrial herbs, sympodial, with short rhizomes. Stems thickened into ovoid to conical pseudobulbs, sheathed by leaf-bases. Leaves in 2 ranks, 2?5, thin, pleated, ribbed. Inflorescences basal racemes, short or long, erect or arching. Flowers resupinate, 1-many, small to large, waxy, white, yellow or green with reddish blotches, labellum paler. Sepals and petals similar, spreading, free or joined at base, lateral sepals joined to column foot forming a pouch. Labellum 3- lobed, side lobes often small, midlobe large with a prominent thickened variously ornamented callus at base. Column short, sometimes 2-winged at tip, with a short foot. Pollinia 4, waxy.
About 20 species from tropical S America.
Labellum with a large fleshy callus at base.
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.