Habit and leaf form. Low, erect or prostrate, much-branched shrubs; evergreen; leptocaul, or pachycaul. Helophytic to xerophytic. Leaves minute to medium-sized; alternate; spiral, or four-ranked; ‘herbaceous’, or leathery; imbricate, or not imbricate; shortly petiolate to sessile; non-sheathing; simple. Leaf blades entire; flat, or rolled; palmately veined; cross-venulate, or without cross-venules. Leaves without stipules. Leaf blade margins flat, or revolute. Stem anatomy. Nodes unilacunar. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous. Pollination mechanism unspecialized.
Inflorescence and flower features. Flowers solitary; axillary; pedicellate to sessile; bracteate; bracteolate (the several bracts passing gradually into bracteoles and sepals); small to medium-sized; fragrant, or odourless; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal; annular (or cup-shaped, truncate or lobed). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; polysepalous; imbricate; exceeded by the corolla to more or less equalling the corolla; regular; persistent. Corolla 5; 1 -whorled; gamopetalous; lobed. Corolla lobes markedly shorter than the tube (usually erect or spreading, or distinctly revolute in A. stomarrhena). Corolla valvate; tubular (elongated and cylindric); regular; hairy adaxially (with 5 tufts or a ring of hairs towards the base; lobes usually bearded but sometimes only bearded at the base), or glabrous adaxially (in A. ciliatum and A. foliosum); white, or cream, or red, or pink, or purple; persistent, or deciduous. Corolla lobes narrowly triangular (erect at the base and spreading towards the apex). Androecium 5. Androecial members adnate (to the corolla); all equal; free of one another (usually), or coherent; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion in the throat of the corolla tube. Stamens becoming exserted, or remaining included; isomerous with the perianth; oppositisepalous; all alternating with the corolla members. Filaments glabrous, or hairy (in A. stomarrhena); long or short, flattened to terete. Anthers separate from one another, or connivent to cohering (slightly, around the style, in A. stomarrhena); all alike (narrowly oblong to linear); attached above the middle or near the top; becoming inverted during development, their morphological bases ostensibly apical in the mature stamens; non-versatile; dehiscing via longitudinal slits (by a single median slit); finally introrse (inverting during development); unilocular, or bilocular; bisporangiate; unappendaged. Pollen shed as single grains; without viscin strands. Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 5 locular. Gynoecium stylate. Styles 1; filiform; attenuate from the ovary; apical; as long as or longer than the corolla tube. Stigmas 1; capitate. Placentation apical. Ovules 1 per locule; pendulous; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy, or fleshy (when mesocarp slightly pulpy); indehiscent; a drupe. The drupes with separable pyrenes, or with one stone. Endocarp hard, bony. Seeds endospermic. Endosperm oily. Seeds wingless. Embryo well differentiated. Cotyledons 2. Embryo straight. Seedling. Germination phanerocotylar.
Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, New South Wales, Victoria, and Tasmania. South-West Botanical Province.
Additional characters Prophylls few, or numerous (in A. pinifolium).