Homalospermum Schauer

Scientific Description

Family Myrtaceae.

Habit and leaf form. Shrubs, or trees (rarely); evergreen; bearing essential oils. Plants with neither basal nor terminal concentrations of leaves. Young stems with stem flanges. To 8 m high. Leptocaul. Helophytic, or mesophytic. Leaves small to medium-sized; alternate; leathery; petiolate; gland-dotted; aromatic; edgewise to the stem, or with ‘normal’ orientation; simple; epulvinate. Leaf blades dorsiventral, or isobilateral, or centric; entire; flat, or rolled, or solid; terete, or semi-terete, or solid/angular; linear, or lanceolate, or oblong, or ovate; obovate; pinnately veined, or parallel-veined, or one-veined; cross-venulate, or without cross-venules. Leaves without stipules; without a persistent basal meristem. Stem anatomy. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite (and protandrous). Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous. Pollination mechanism unspecialized.

Inflorescence and flower features. Flowers solitary; axillary (on unmodified shoots); subsessile to sessile; bracteate, or ebracteate; (bi) bracteolate, or ebracteolate; small to medium-sized; regular; 5 merous; cyclic. Free hypanthium present (petals ‘inserted on the calyx’); campanulate. Hypogynous disk present. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; polysepalous; imbricate, or valvate; exceeded by the corolla. Corolla present; 5; 1 -whorled; polypetalous; imbricate; regular; white, or pink, or white and pink. Petals obovate. Androecial members indefinite in number. Androecium usually 30–35. Androecial members branched. Androecial sequence determinable, or not determinable. Androecial members maturing centripetally; free of the perianth; all equal, or markedly unequal; free of one another. Stamens 30–35; shorter than the petals; polystemonous; alternisepalous and oppositisepalous; both opposite and alternating with the corolla members; erect in bud, or inflexed in bud. Filaments with prominent oil glands; not geniculate; filiform. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; cells parallel; tetrasporangiate; appendaged (with a terminal gland and 2 abaxial ridges on each side of the connective), or unappendaged. The anther appendages apical. Gynoecium 3–5 carpelled. The pistil 3–5 celled. Gynoecium syncarpous; eu-syncarpous; inferior, or partly inferior. Ovary plurilocular; 3–5 locular. Ovary summit with radiating bands of hairs delimiting the cells. Epigynous disk present, or absent. Gynoecium stylate. Styles 1; simple; apical. Stigmas 1; peltate. Placentation axile. Ovules 50 per locule (i.e. ‘many’); pendulous to horizontal (on the peltate placenta); non-arillate; hemianatropous (and peltate).

Fruit and seed features. Fruit non-fleshy (woody); dehiscent; a capsule (3–5-valved). Capsules septicidal, or loculicidal, or denticidal, or circumscissile. Fruit few-seeded. Seeds non-endospermic; disc-shaped, with a central point of attachment; winged. Seed wings encircling body. Cotyledons 2.

Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia. South-West Botanical Province.