Lophostemon Schott

Scientific Description

Family Myrtaceae.

Habit and leaf form. Trees, or shrubs (occasionally); evergreen; laticiferous (oil ducts in the petioles and young stems yielding a milky exudate); bearing essential oils. Plants with neither basal nor terminal concentrations of leaves; to 3–18 m high. Leptocaul. Helophytic to xerophytic. Leaves small to large; alternate (pseudoverticillate at the ends of branchlets); leathery; petiolate; gland-dotted; aromatic; edgewise to the stem, or with ‘normal’ orientation; simple; epulvinate. Leaf blades dorsiventral, or isobilateral, or centric; entire; flat; linear, or lanceolate, or oblong, or ovate; ovate, or obovate, or elliptic; pinnately veined, or parallel-veined, or one-veined; cross-venulate, or without cross-venules. Mature leaf blades adaxially glabrous, or pubescent, or villous; abaxially glabrous, or pubescent, or villous. Leaves without stipules; without a persistent basal meristem. Leaf anatomy. Hairs present, or absent. Stem anatomy. 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 aggregated in ‘inflorescences’; in cymes. Inflorescences simple, or compound. The terminal inflorescence unit cymose. Inflorescences axillary. Flowers pedicellate; (bi) bracteolate. Bracteoles deciduous (free). Flowers small to medium-sized; regular; 5 merous; cyclic. Free hypanthium present (petals ‘inserted on the calyx’); campanulate to turbinate; hardly extending beyond ovary. 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; regular; persistent (usually), or not persistent (in L. confertus). Sepals ovate (to semicircular). Corolla present; 5; 1 -whorled; polypetalous; imbricate; regular; white to cream. Petals orbicular. Androecial members indefinite in number. Androecium 60–450. Androecial members branched. Androecial sequence determinable, or not determinable. Androecial members if ‘many’, maturing centripetally; free of the perianth; all equal, or markedly unequal; coherent; 5 - adelphous (bundled). The androecial groups opposite the petals. Stamens 60–450; attached on the rim of the hypanthium; becoming exserted (equalling petals); polystemonous; alternisepalous; all opposite the corolla members; erect in bud, or inflexed in bud. Filaments inflexed to decumbent. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged (with connective gland), or unappendaged. Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium syncarpous; eu-syncarpous; partly inferior. Ovary plurilocular; 3 locular. Ovary summit glabrous. Epigynous disk absent. Gynoecium stylate. Styles 1; apical. Stigmas 1; capitate. Placentation axile (in L. confertus and L. suaveolens), or parietal (or pseudoaxile in other species). Ovules 50 per locule (‘many’); ascending; randomly arranged on placentas; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 3 celled. Seeds non-endospermic; linear-cuneate; minute to small; winged, or wingless. Cotyledons 2; obvolute. Embryo straight.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, Queensland, and New South Wales. Northern Botanical Province.