Habit and leaf form. Herbs; evergreen. Switch-plants; with the principal photosynthesizing function transferred to stems (culms). Leaves well developed, or much reduced (the blade being much reduced). Perennial. Young stems cylindrical (striate); not breaking easily at the nodes. Stem internodes solid, or hollow. Rhizomatous. Leaves alternate; distichous, or spiral; leathery, or membranous; sessile; sheathing (and more or less reduced to the sheaths). Leaf sheaths with free margins (appressed, persistent). Leaves simple; with a persistent basal meristem, and basipetal development. Vegetative anatomy. Plants with silica bodies. Leaf anatomy. Leaf blade epidermis conspicuously differentiated into ‘long’ and ‘short’ cells, or without differentiation into ‘long’ and ‘short’ cells. Guard-cells not ‘grass type’, or ‘grass type’. Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Unisexual flowers present. Plants dioecious. Female flowers with staminodes, or without staminodes. Male flowers with pistillodes, or without pistillodes. Floral nectaries absent (nectaries absent). Anemophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in ‘spikelets’. Inflorescences scapiflorous, or not scapiflorous; terminal and axillary; mostly much branched, with several or many spikelets terminal and axillary at upper nodes of a usually branched inflorescence. Flowers bracteate; bracteolate, or ebracteolate; cyclic. Perigone tube absent. Perianth of ‘tepals’; members 4–6; 2 -whorled; isomerous, or anisomerous; sepaloid. Fertile stamens present, or absent (when female). Androecium 3. Androecial members free of the perianth; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 3; becoming exserted; reduced in number relative to the adjacent perianth, or isomerous with the perianth; oppositiperianthial (opposite the inner perianth members). Anthers dorsifixed; versatile, or non-versatile; dehiscing via longitudinal slits; introrse, or latrorse; bisporangiate, or tetrasporangiate; appendaged, or unappendaged. Pollen shed as single grains. Fertile gynoecium present, or absent (male flowers). Gynoecium 1–3 carpelled. The pistil 1–2 celled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious; superior. Ovary unilocular, or plurilocular; 1–2 locular; sessile to stipitate. Gynoecium stylate. Styles 1, or 2; when 2, partially joined (basally). Placentation when plurilocular, axile to apical. Ovules in the single cavity (when unilocular) 1; (when plurilocular) 1 per locule; funicled, or sessile; pendulous; non-arillate; orthotropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule (woody, broadest near the apex, heart-shaped if 2 carpels develop, obconical if only 1 carpel develops, with prominent stylar beak). Capsules loculicidal. Fruit 1–2 seeded. Seeds oblong, with a longitudinal furrow encircling the seed or on one side only; copiously endospermic. Embryo weakly differentiated. Testa surface with slightly convex, lobed cells. Seedling. Hypocotyl internode absent. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling cataphylls absent. First leaf centric. Primary root ephemeral.
Additional characters Perianth of male flowers of ‘tepals’; 4–6 (tepals membranous, outer tepals keeled, inner tepals flat). Perianth of female flowers of ‘tepals’; 4. Stems glabrous, or pubescent; branched (usually), or simple; dimorphic (fertile culms taller and less branched than the shorter, much branched and strongly flexuose vegetative culms). Male spikelets many-flowered. Female spikelets 1-flowered to several-flowered (spikelets 1–3-flowered, mostly terminal). Not caespitose.