Habit and leaf form. Herbs; bearing essential oils, or without essential oils (?); resinous, or not resinous (?). Annual, or perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Helophytic, or mesophytic. Leaves minute to medium-sized; alternate (usually), or whorled (in A. glomeratus); ‘herbaceous’; petiolate, or sessile; more or less sheathing. Leaf sheaths with free margins. Leaves gland-dotted, or not gland-dotted (?); aromatic, or foetid, or without marked odour (?); simple; peltate, or not peltate (?); pulvinate, or epulvinate (?). Leaf blades dissected; lobed, or ternately divided into linear segments which may be further divided into 2 or 3 oblong lobes; pinnately veined, or palmately veined, or parallel-veined (?). Leaves without stipules; without a persistent basal meristem. Leaf anatomy. Hairs present, or absent. Stem anatomy. Nodes multilacunar, or tri-lacunar (?). Secondary thickening developing from a conventional cambial ring, or anomalous (?); from a single cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite, or hermaphrodite and functionally male, or functionally male and functionally female. Unisexual flowers present (together with bisexual or female flowers in the same inflorescence), or absent (apparently, when ‘almost all’ flowers bisexual). Plants andromonoecious (mostly), or monoecious (in A. forsythii), or hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in umbels, or in heads (formed by contraction of the simple umbel). The terminal inflorescence unit cymose, or racemose (?). Inflorescences terminal; sessile or pedunculate; with involucral bracts. Involucral bracts varying from densely woolly to glabrous. Inflorescences pseudanthial. Flowers pedicellate, or sessile; bracteate; small; regular; 5 merous (except for the gynoecium); cyclic; tetracyclic, or tricyclic (when corolla absent). Free hypanthium absent. Perianth with distinct calyx and corolla, or sepaline; 5, or 10; 2 -whorled, or 1 -whorled; isomerous; white to cream, or green, or pink. Calyx present; 5; 1 -whorled; gamosepalous; shortly 5- lobed, or entire; persistent; with the median member posterior. Corolla present, or absent; when present, 5; 1 -whorled; polypetalous; valvate; regular. Fertile stamens present, or absent (female flowers). Androecium 5. Androecial members free of the perianth; all equal to markedly unequal (?); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; inflexed in bud. Filaments filiform. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 2 carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious; inferior. Ovary unilocular; 1 locular. Gynoecium median. Epigynous disk present. Gynoecium stylate. Styles 2; free (their bases thickened, forming a prominent, gland-like stylopodium crowning the ovary); apical. Stigmas wet type; non-papillate; Group IV type. Ovules pendulous; epitropous; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; indehiscent; a single ovoid carpel. Seeds endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous; straight. Seedling. Germination phanerocotylar.
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, New South Wales, Victoria, Australian Capital Territory, and Tasmania.