Habit and leaf form. Herbs; non-laticiferous and without coloured juice. Annual, or perennial; plants with a basal concentration of leaves; rhizomatous and tuberous (rhizomes often thick, woody, bearing simple roots which terminate in storage tubers), or bulbaceous (T. bulbosum). Hydrophytic, or helophytic; when hydrophytic, rooted. Leaves emergent, or submerged (rarely); medium-sized to very large; alternate; spiral, or spiral to distichous (‘spirodistichous’); sessile; sheathing. Leaf sheaths with free margins. Leaves edgewise to the stem, or with ‘normal’ orientation; simple; epulvinate. Leaf blades entire; more or less flat (and strap-like, often thickened and spongy basally), or solid (then terete, rarely); linear; parallel-veined. Leaves eligulate, or ligulate (T. striatum); with stipules, or without stipules. Axillary scales present. Leaves with a persistent basal meristem, and basipetal development. Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male, or functionally female. Unisexual flowers present, or absent. Plants hermaphrodite (protogynous), or dioecious. Anemophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence few-flowered to many-flowered. Flowers in racemes. The terminal inflorescence unit racemose. Inflorescences scapiflorous; terminal; usually dense and spike-like. Flowers pedicellate; ebracteate; small; regular; 3 merous; cyclic. Perigone tube absent. Perianth of ‘tepals’; 3, or 6 (each segment incurved over an anther), or 1 (rarely); 2 -whorled (usually), or 1 -whorled; isomerous; free; sepaloid; without spots; similar in the two whorls; usually pink to red (at least in distal part); deciduous. Fertile stamens present, or absent (female flowers). Androecium 6 (usually), or 3 (when the inner whorl missing), or 1 (rarely). Androecial members adnate (to the base of the perianth segments); free of one another; 1 -whorled, or 2 -whorled (then 3 + 3). Androecium exclusively of fertile stamens. Stamens 6, or 3, or 1; isomerous with the perianth, or diplostemonous; filantherous, or with sessile anthers. Anthers dehiscing via longitudinal slits; extrorse; tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium (2–)3–6(–8) carpelled (usually 3 fertile carpels alternating with 3 sterile carpels). Carpels isomerous with the perianth. Gynoecium apocarpous to syncarpous; eu-apocarpous to semicarpous, or synovarious; superior. Carpel when apocarpous, stylate; apically stigmatic; 1 ovuled. Placentation basal. Ovary when syncarpous, plurilocular. Gynoecium stylate. Stigmas dry type; papillate; Group II type. Placentation basal to axile. Ovules when syncarpous, 1 per locule; ascending; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; an aggregate (when apocarpous or semicarpous), or not an aggregate (when syncarpous). The fruiting carpel dehiscent, or indehiscent; an achene (follicle-like, often with hooks, spurs, keels or wings, each 1-seeded, all separating and falling at maturity). Fruit of syncarpous gynoecium a schizocarp. Mericarps comprising achenes, or comprising follicles. Seeds narrowly elliptic; non-endospermic; with starch. Cotyledons 1. Embryo straight. Seedling. Hypocotyl internode absent. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling non-macropodous. Seedling cataphylls absent. First leaf centric. Primary root ephemeral.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. Northern Botanical Province, Eremaean Botanical Province, and South-West Botanical Province.