Epiphytic herbs. Pseudobulbs fleshy, fusiform, or subconic; roots often with many secondary, slender, erect, spinous rootlets which form dense mats about the base of the plants. Leaves plicate, strongly nerved, the blades deciduous; the per-sistent imbricating bases closely enveloping the pseudobulbs, armed at the apex with short, sharp spines. Inflorescences arching or pendulous racemes from the base of the pseudobulbs. Flowers few or many, often large and showy, unisexual or perfect. Sepals aud petals in all forms free, subequal, fleshy or membranaceous, part or all of them spreading or reflexed and connivent at the base. The genus is divided by Mansfeld into two distinct sections. In CLOWESIA: flowers perfect (containing both a functional stigmatic surface and a fertile anther); column without elongate antenna-like processes; lip membranaceous or fleshy. In ORTHOCATASETUM: flowers unisexual, the staminate and pistillate forms strikingly dissimilar and usually produced on separate scapes; staminate flowers (those most frequently seen) usually many, often conspicuously colored, on an arching or pendent raceme; lip membranaceous, fleshy, spreading, concave or galeate, the margins entire, lobulate, emarginate, crenate, fimbriate or dentate; column erect, footless, the under-side usually with two elongate antenna-like processes which are extremely sensitive when touched, ejecting the pollinia with considerable force. Anther terminal, operculate, incumbent, convex, 1-celled or imperfectly 2-celled; pollinia 4, waxy, in 2 pairs, or 2-lobed or 2-sulcate. Pistillate flowers less frequently produced, usually few, on short, erect or arching racemes. Lip usually very fleshy and galeate, with or without a thickened margin. Column short and stout, without antennae; functional stigmatic surface present.
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