Habit and leaf form. Herbs. Annual, or perennial. Leaves basal, or cauline. Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves (rarely). Helophytic, or hydrophytic (E. setaceum). Leaves of aquatic species submerged; alternate; spiral, or distichous; sessile; sheathing (but at the base only). Leaf sheaths with free margins. Leaves simple; epulvinate. Leaf blades entire; linear (grasslike); parallel-veined (often fenestrate); without cross-venules. Leaves eligulate. Leaf blade margins entire. Leaf anatomy. Guard-cells ‘grass type’. Hairs absent, or present (rarely, at base). Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Fertile flowers functionally male and functionally female. Unisexual flowers present. Plants monoecious. Male flowers with pistillodes. Floral nectaries present (black gland at apex of androphore), or absent (sometimes). Nectar secretion from the perianth (from the mouth or the inside of the perigone tube). Anemophilous, or entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in heads; not in ‘spikelets’. The terminal inflorescence unit racemose. Inflorescences scapiflorous (scape erect, usually longer than leaves, rarely poorly developed); terminal; with involucral bracts (flowers not exceeding the imbricate bracts); pseudanthial. Flowers bracteate; minute, or small; regular to very irregular; when irregular, zygomorphic. The floral asymmetry when present, involving the perianth and involving the androecium. Flowers (1–)2 merous, or 3 merous; cyclic. Floral receptacle developing an androphore. Perigone tube present. Hypogynous disk absent. Perianth with distinct calyx and corolla, or sepaline, or petaline, or of ‘tepals’, or absent; 2–6; 2 -whorled, or 1 -whorled; isomerous, or anisomerous; different in the two whorls. Calyx (if the outer whorl so interpreted) (1–)2–3; 1 -whorled; polysepalous, or gamosepalous (with a basal tube or spathaceous in male flowers); unequal but not bilabiate, or regular. Corolla (if the inner whorl so interpreted) 2, or 3; 1 -whorled; polypetalous; regular, or unequal but not bilabiate (the members sometimes dimorphic). Fertile stamens present, or absent (female flowers). Androecium 4, or 6 (twice the number of inner perianth segments). Androecial members adnate (to the corolla); free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens. Stamens 4, or 6; diplostemonous; alternisepalous, or oppositisepalous (when reduced to one whorl), or alternisepalous and oppositisepalous. Anthers basifixed; dehiscing via longitudinal slits; introrse; bisporangiate, or tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 2 carpelled, or 3 carpelled. The pistil 2 celled, or 3 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary plurilocular; 2 locular, or 3 locular; sessile to stipitate. Styles 1; with 2 or 3 simple or bifid stigmatic branches, without stylar appendages; apical. Stigmas 2, or 3; dry type; non-papillate; Group II type. Placentation basal. Ovules 1 per locule; pendulous; non-arillate; orthotropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds ellipsoid; copiously endospermic. Endosperm not oily. Seeds with starch. Embryo rudimentary at the time of seed release; lenticular. Testa variously hairy or sculptured. Seedling. Hypocotyl internode absent. Mesocotyl absent. Cotyledon hyperphyll compact; non-assimilatory. Coleoptile absent. First leaf dorsiventral. Primary root ephemeral.
Additional characters Perianth of male flowers with distinct calyx and corolla (the inner whorl may be somewhat obscure), or of ‘tepals’ (the 2 whorls separated by the androphore); 4–6. Perianth of female flowers with distinct calyx and corolla, or sepaline, or petaline, or of ‘tepals’ (the 2 whorls separated by the floral axis), or absent (in E. australasicum); 3–6 (when 2-whorled), or 2–3 (when only inner or outer whorl present).