Description from Flora of China
Herbs, epiphytic or lithophytic. Stem erect, often pseudobulbous or fusiform, simple or superposed, with 1 to several leaves. Leaves conduplicate, often narrowly oblong or oblong, sheathing and articulate at base. Inflorescences terminal, racemose or paniculate, few to many flowered; peduncle often enclosed in scarious sheaths. Flowers not resupinate, small or sometimes medium-sized. Sepals connivent or spreading; dorsal sepal free; lateral sepals adnate to column foot forming a mentum. Petals smaller, usually linear; lip superior, entire or 3-lobed, base articulate with column foot, spurless; disk often farinaceous (pseudopollen). Column short, with conspicuous column foot; pollinia 4 (unequal in size, in 2 pairs) or 2 (each deeply cleft), waxy, with a small stipe and a viscidium.
About 200 species: centered in Africa, some species in tropical America, and one pantropical species widespread in Asia from Sri Lanka and India eastward to Sulawesi and the Philippines, including China.
(Authors: Chen Xinqi (陈心启 Chen Sing-chi); Jeffrey J. Wood)