Greek pleuron – rib; thallos – a branch; an allusion to the many rib-like stems of most species.
Epiphytic, epilithic or rarely terrestrial herbs, sympodial, with short or long creeping rhizomes. Stems not thickened into pseudobulbs, tufted, usually short, erect, jointed, sheathed. Leaves apical, usually solitary, leathery to fleshy, stalkless or stalked. Inflorescences terminal or rarely lateral racemes, often 1-sided, erect or arching. Flowers resupinate, 1-many, small, variously coloured. Sepals similar, dorsal free or partly joined to laterals at base, laterals partly or entirely fused and concave at base. Petals smaller than sepals, sometimes clubbed at tip. Labellum small, entire or 3-lobed, clawed. Column short, often winged, with or without a short foot. Pollinia 2, waxy.a genus much in need of revision.
About 900 species from tropical and sub tropical N, C and S America.
Usually small tufted plants lacking pseudobulbs; small bright flowers often in 1-sided racemes.
Luer (1986).
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.