Habit and leaf form. Herbs (the 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 cylindrical (striate); not breaking easily at the nodes. Stem internodes 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’. Inflorescences scapiflorous, or not scapiflorous; terminal, or axillary; male and female inflorescences similar, of large erect spikelets terminal or 2 or 3 at upper nodes, the spikelets with several sterile glumes toward both base and apex; glumes rigid, dark brown or black, obtuse or with a short rigid acute tip. Flowers bracteate; bracteolate, or ebracteolate; cyclic. Perigone tube absent. Perianth of ‘tepals’; members 6 (2 outer tepals keeled and with dense red-brown hairs along the keel toward the apex, inner tepals flat); 2 -whorled; isomerous; 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; 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 2 carpelled, or 3 carpelled. The pistil 2 celled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious; superior. Ovary plurilocular; 2 locular; sessile to stipitate. Gynoecium stylate. Styles 2; partially joined. Placentation axile to apical. Ovules 1 per locule; funicled, or sessile; pendulous; non-arillate; orthotropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 2 seeded. Seeds copiously endospermic. Embryo weakly differentiated. 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’; 6. Perianth of female flowers of ‘tepals’; 6. Stems glabrous; simple, or branched (occasionally, 1 or 2 branches only); not dimorphic. Male spikelets many-flowered (10–20-flowered). Female spikelets many-flowered (10–20-flowered). Caespitose. Spikelets more than 10 mm long.