Annual or perennial; tufted, rhizomatous or stoloniferous. Leaves in basal, vegetative shoots and inserted distichously along stems (culms); blade usually ± linear; sheath open or closed, with a commonly membranous ligule at junction with base of blade. culms herbaceous or woody, jointed, internodes usually hollow. fruit an indehiscent grain (caryopsis), pericarp sometimes free, ocassionally fleshy.