Habit and leaf form. Small trees, or shrubs; evergreen; leptocaul, or pachycaul. Helophytic to xerophytic. Leaves minute to small; alternate; spiral, or four-ranked; erect to spreading, ‘herbaceous’, or leathery; imbricate; petiolate to sessile; non-sheathing; simple. Leaf blades entire; flat, or rolled; palmately veined, or parallel-veined (in M. ‘B’); 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, or functionally male, or functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or polygamomonoecious, or gynodioecious (in M. linifolia). Entomophilous, or ornithophilous. Pollination mechanism unspecialized.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary. Inflorescence few-flowered. Flowers in spikes, or in racemes. Inflorescences terminal, or axillary. Flowers bracteate, or ebracteate (in M. elliptica); bi- bracteolate. Bracteoles persistent, or deciduous. Flowers small; fragrant, or odourless; regular; 4–5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal; of separate members, or annular (and lobed or toothed). Perianth with distinct calyx and corolla; 9, or 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; polysepalous; imbricate; exceeded by the corolla; regular; persistent. Corolla 5 (usually), or 4; 1 -whorled; gamopetalous; lobed (lobes glabrous, spreading in male flowers, more erect in female flowers); valvate; usually campanulate; regular; more or less glabrous abaxially, or hairy abaxially (in M. tamariscina); more or less glabrous adaxially; white to cream; persistent, or deciduous. Fertile stamens present, or absent (from female flowers). Androecium 5. Androecial members adnate (to the corolla); all equal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion in the throat of the corolla tube. Stamens becoming exserted (partially), or remaining included; isomerous with the perianth; oppositisepalous; all alternating with the corolla members. Filaments glabrous; short. Anthers basifixed, or adnate; 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. Fertile gynoecium present, or absent (from male flowers). Gynoecium 2(–4) carpelled. The pistil 1–2(–4) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary unilocular, or plurilocular; 1–2(–4) locular. Gynoecium stylate. Styles 1; short; attenuate from the ovary; apical. Stigmas 1; lobed; truncate, or clavate, or capitate. Placentation apical. Ovules 1 per locule; pendulous; non-arillate; anatropous.
Fruit and seed features. Fruit somewhat fleshy; indehiscent; a drupe. The drupes with one stone. 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, Queensland, New South Wales, Victoria, and Tasmania.
Additional characters Prophylls few.