45. Pleurothallis R. Brown, Hortus Kew. 5: 211. 1813.
[Greek pleuron, rib, and thallos, branch, referring to cespitose, slender, aerial shoots]
C. A. Luer
Herbs epiphytic. Roots fibrous. Stems erect, stout; sheaths tubular, variously enclosing stems. Leaves 1, erect, sessile or petiolate; blade leathery. Inflorescences terminal [axillary], 1–several lax or clustered racemes [solitary flower]. Flowers sometimes distichous, resupinate, opening simultaneously; sepals distinct [variously connate], subequal, membranous [thickly fleshy], pubescent [smooth or verrucose]; petals glabrous [verrucose, papillose, pubescent, ciliate, or fringed]; lip simple [2–5-lobed], membranous [thickly fleshy], callous, base loosely articulate to base of column or apex of column foot [sometimes inflexibly adnate]; column semiterete, stout [slender], winged [wingless], with or without column foot, apex with anther exposed or hooded; anther apical or adaxial; ovary articulate between ovary and minute curved pedicel; pollinia 2, pyriform with viscidium [spheric without viscidium] and caudicles [naked, with or without viscidium]; stigma adaxial [apical], 1–2-lobed; rostellum apical or adaxial. Fruits capsules, deciduous at pedicel (ca. 1 mm), ellipsoid, 3-valved.
Species ca. 2500 (1 in the flora): tropics, s Florida, s Mexico, West Indies, Central America, South America.
Pleurothallis is the largest genus in the subtribe Pleurothallidinae, and perhaps in the Orchidaceae.