Herbs, epiphytic or lithophytic, monopodial, small. Roots radiate, appressed to tree trunk or branch, green and photosynthetic in rainy season, whitish or grayish in dry season, flattened or terete, rather long and stout. Stems short, nearly invisible. Leaves absent or reduced to tiny brown scales. Inflorescences lateral, short; rachis slowly elongating, with flowers opening in succession 1 or 2 at a time; floral bracts persistent, alternate. Flowers usually lasting only a day, small. Sepals and petals free and widely spreading or connate at base or below middle into a tube. Lip entire or 3-lobed, attached to base of column, spurred or saccate, often with an apical reflexed tooth or bristle; spur globose to cylindric. Column short, stout, footless; rostellar projection variable; anther cap terminal, often beaked; pollinia 4, waxy, subglobose, equal, separate from each other, with a common stipe and an oblong or elliptic viscidium.

Between 120 and 180 species: tropical Africa through tropical Asia to Australia and the Pacific islands; three species (one endemic) in China.

(Authors: Chen Xinqi (陈心启 Chen Sing-chi); Jeffrey J. Wood)