Habit and leaf form. Shrubs (with leafy stems); deciduous (the caducous leaves leaving annular scars). Plants with neither basal nor terminal concentrations of leaves. Helophytic, or mesophytic, or xerophytic. Leaves alternate; spiral; leathery; petiolate. Petioles winged (and stem-clasping). Leaves sheathing, or non-sheathing; gland-dotted; simple; epulvinate. Leaf blades entire; parallel-veined. Leaves with stipules, or without stipules; without a persistent basal meristem. Leaf anatomy. Hairs absent. Stem anatomy. Nodes tri-lacunar. Secondary thickening anomalous; via concentric cambia.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous. Entomophilous; via hymenoptera, via lepidoptera, and via diptera.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in racemes. The terminal inflorescence unit cymose. Inflorescences scapiflorous, or not scapiflorous; terminal, often branched and arranged in leafy panicles. Flowers uni- bracteate; bi- bracteolate; small; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous (forming a 5 ribbed tube). Calyx lobes markedly shorter than the tube. Calyx erect; glabrous; plicate in bud; exceeded by the corolla; regular; coriaceous; persistent. Corolla 5; 1 -whorled; gamopetalous (basally into a very short tube, each member above with a long claw and spreading limb); imbricate, or contorted; regular; white; not fleshy (leathery); deciduous above and persistent below. Androecium 5. Androecial members adnate (to the corolla); coherent (forming a persistent tube); 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion near the base of the corolla tube. Stamens isomerous with the perianth; alternisepalous; all opposite the corolla members. Anthers narrowly oblong, sagittate at the base; basifixed; versatile, or non-versatile; dehiscing via longitudinal slits; latrorse; tetrasporangiate. Gynoecium 5 carpelled. The pistil 1 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; synovarious; superior. Ovary unilocular; 1 locular. Styles 5; free; apical. Stigmas 5; 1 - lobed; capitate; dry type; papillate; Group II type. Placentation basal. Ovules in the single cavity 1; pendulous (from a long, basally attached funicle); anatropous (or circinnotropous).
Fruit and seed features. Fruit with spongy mesocarp; dehiscent; a capsule (narrowly cylindric, surrounded at the base by the persistent calyx). Capsules dehiscing along the 5 angles. Seeds endospermic, or non-endospermic; winged. Embryo well differentiated. Cotyledons 2. Embryo straight. Seedling. Germination phanerocotylar.
Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.
Special features. Mangroves (although pneumatophores absent in A. annulata).
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province and Eremaean Botanical Province.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/