Herbs annual or, usually perennial, (Chinese species) rooting from nodes toward base of stem and with erect or ascending flowering shoots. Stems usually dwarf, fleshy; vascular bundles free, scattered. Prophylls absent. Leaves alternate, opposite, or whorled, main lateral veins all basal; reticulate veins inconspicuous. Flowers bisexual, very small, often within depressions in rachis, sessile. Inflorescence a spike, usually erect, terminal or axillary, rarely leaf-opposed, solitary, paired, or clustered; rachis as thick or slightly thicker than peduncle; bracts ± orbicular, peltate (sometimes oblong and/or not peltate). Stamens 2; filaments short, thecae ± globose, ellipsoid, or cylindric. Ovary 1-loculed; ovule 1; stigma 1, rarely 2-cleft, globose, apex obtuse or acute, beaked or brushlike, lateral or terminal. Fruit a very small, sticky nutlet, often partly enclosed in pit in rachis, sometimes distinctly curved.

About 1000 species: widely distributed in tropical and subtropical regions; seven species (two endemic, one introduced) in China, mostly growing on trees or moss-covered rocks.