Habit and leaf form. Aquatic herbs; laticiferous. Annual, or perennial; rhizomatous, or tuberous (sometimes). Hydrophytic; rooted. Cladodes thick-textured. Leaves emergent, or floating; medium-sized to very large; alternate; spiral; petiolate; simple; peltate, or not peltate. Leaf blades entire; basically palmately veined; cross-venulate; strongly cordate, or sagittate (or cleft at the base). Leaves with stipules (the stipules median-axillary), or without stipules. Leaf blade margins entire (to sinuate), or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent. Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers solitary; large (usually emergent, showy); often fragrant; regular; partially acyclic. The perianth acyclic and the androecium acyclic. Free hypanthium absent. Perianth with distinct calyx and corolla; (9–)10–54(–55); free. Calyx (3–)4(–5) (hypogynous); polysepalous; imbricate. Corolla c. 6–50 (hypogynous or epigynous); inserted irregularly or more or less in whorls; polypetalous; imbricate. Androecium 20–750. Androecial members maturing centripetally; free of the perianth; free of one another; spiralled. Androecium exclusively of fertile stamens. Stamens 20–750. Staminal insertion at various levels up the sides of the receptacle which appears to surround the ovary, the stamens often curving over the stigmas. Stamens petaloid (outermost), or filantherous (innermost). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; bilocular; tetrasporangiate; appendaged (formed by extension of the connective), or unappendaged. Pollen shed as single grains. Gynoecium 5–35 carpelled. The pistil 5–35 celled. Gynoecium syncarpous; semicarpous, or eu-syncarpous; superior to partly inferior. Ovary plurilocular; 5–35 locular. Stigmas 5–35 (radiating from the floral axis, together forming a broad, circular, somewhat depressed stigmatic disc across the ovary summit; floral axis projecting from the centre of the disc). Placentation more or less parietal (or ovules more or less scattered). Ovules 10–100 per locule (i.e. ‘many’); arillate; anatropous.
Fruit and seed features. Fruit fleshy (spongy); irregularly dehiscent; a berry (capped by the stigmatic disc, retracted and ripening underwater); enclosed in the fleshy receptacle; numerous-seeded. Seeds endospermic. Perisperm present. Seeds arillate (aril mucilaginous, buoyant). Cotyledons 1, or 2. Embryo chlorophyllous; straight. Seedling. Germination cryptocotylar.
Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, Queensland, and New South Wales. Northern Botanical Province, Eremaean Botanical Province, and South-West Botanical Province.
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