Habit and leaf form. Herbs (base pubescent); evergreen. Switch-plants; with the principal photosynthesizing function transferred to stems (culms). Leaves well developed, or much reduced (the blade being much reduced or absent). Perennial. Young stems 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 (persistent, appressed). 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’, or not in ‘spikelets’ (spikelet structure obvious in males or obscured by clustering in both males and females). Inflorescences scapiflorous, or not scapiflorous; terminal; male and female inflorescences similar or dissimilar, branched. Flowers bracteate; bracteolate, or ebracteolate; cyclic. Perigone tube absent. Perianth of ‘tepals’; members 4–6 (acute or acuminate, outer tepals keeled); 2 -whorled; isomerous, or anisomerous; sepaloid; hyaline or scarious. 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; 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 3 carpelled. The pistil 1 celled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious; superior. Ovary unilocular; 1 locular; sessile to stipitate. Gynoecium stylate. Styles 3; partially joined (basally). Ovules in the single cavity 1; funicled, or sessile; pendulous; non-arillate; orthotropous.
Fruit and seed features. Fruit non-fleshy; indehiscent; a nut (small, shed with enclosing glume, bract and persistent perianth, the fruiting perianth with ovate tepals less than 2 times as long as the fruit); 1 seeded. Seeds copiously endospermic. Embryo weakly differentiated. Testa smooth (with a pattern of subangular 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. Perianth of female flowers of ‘tepals’; 5–6 (tepals rigid). Stems densely pubescent (with appressed or spreading ‘fan-hairs’), or glabrous; simple (below the inflorescence). Male spikelets erect or pendulous. Not caespitose. Female spikelets compound (with small bracts between the flower and subtending glume) (with clusters (true spikelets) of 3–5 very small flowers each with 1 bract on the ‘flower stalk’ crowded into larger aggregations, the true spikelet acting as the dispersal unit). Male flowers with a globular swollen base. Pericarp thin-textured.