Habit and leaf form. Trees, or shrubs (covered with small scurfy scales). Plants unarmed. To 8–25 m high. Mesophytic. Not heterophyllous. Leaves medium-sized; alternate; spiral; leathery; non-sheathing; simple. Leaf blades dorsiventral; entire; ovate, or oblong; pinnately veined, or palmately veined. Mature leaf blades adaxially scaly (peltate); abaxially scaly (peltate). Leaf anatomy. Hairs absent; complex hairs absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers solitary; axillary; medium-sized to large; regular; 5 merous; tetracyclic. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed; lobulate (5-lobed); valvate; exceeded by the corolla; regular. Calyx lobes triangular. Epicalyx present (of connate caducous bracteoles). Corolla present; 5; 1 -whorled; polypetalous (adnate to the base of the staminal column); hairy abaxially (slightly); glabrous adaxially; pink, or purple (i.e. pale pink to mauve). Androecium present. Androecial members indefinite in number. Androecium 50–100 (1.e. ‘many’). Androecial members adnate; all equal; coherent (connate; the filaments fused in a column surrounding the style); 1 - adelphous (the tube attached to the petals); 1 -whorled. Androecium exclusively of fertile stamens (or rather, half-stamens, each having only a half anther). Stamens 50–100. Anthers dehiscing via longitudinal slits; introrse; unilocular. Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 5 locular. Gynoecium stylate. Styles 1; more than 4-branched (5-branched); apical. Stigmas 5. Placentation axile. Ovules 5–10 per locule (i.e. ‘several’).
Fruit and seed features. Fruit 20–30 mm long; non-fleshy; hairy; dehiscent; a capsule (ovoid, covered with spicules). Capsules loculicidal. Dispersal unit the seed. Seeds endospermic (copious); medium sized; not conspicuously hairy. Testa more or less soft and fleshy.
Geography, cytology, number of species. World distribution: Australia. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Queensland, and New South Wales. South-West Botanical Province. A genus of 1 species; 1 species in Western Australia; 0 endemic to Western Australia.
Etymology. From Lagunaea, the name of a related genus in which the only species was once placed.