Greek physa – bellows; siphon – tube; the tube formed by the fused sepals is inflated at the base.
Epiphytic or epilithic herbs, sympodial, with creeping rhizomes. Stems not thickened into pseudobulbs, tufted, slender, erect or ascending, sheathed. Leaves apical, solitary, leathery to fleshy, stalkless or stalked. Inflorescences terminal racemes, often 1-sided, erect or arching. Flowers resupinate, many, small, variously coloured. Sepals similar, usually fused for more than half their length into a tube, inflated at base, free part spreading. Petals very small, concealed in sepal-tube. Labellum small, entire or 3-lobed, fleshy, channelled, concealed in sepal tube. Column short, erect, 3-lobed. Pollinia 2, waxy.
This genus is often included in Pleurothallis R. Br., from which it differs by the tubular basal part to the sepals.
About 20 species from Mexico, C and S America.
Sepals joined for more than half their length, forming an inflated tube.
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.
