Perennials. Rhizome present, in caespitose forms often very short-noded. Stem with several basal cataphylls, i.e. leaves inserted at abbreviated basal nodes, mostly reduced to sheath with no or tiny blade; uppermost cataphylls rarely with well developed blade. Lower inflorescence bract erect, forming an apparent prolongation of the stem, inflorescence therefore pseudolateral. Stem and leaves of mature plants terete, consisting of a parenchymatous cylinder with a pith of specialized, usually conspicuously aerenchymatic tissue. Each flower with bract and one bracteole at base of pedicel, and two bracteoles at base of the flower.