Baeckea L.

Scientific Description

Common name. Baeckeas. Family Myrtaceae.

Habit and leaf form. Shrubs; evergreen; bearing essential oils. Plants with neither basal nor terminal concentrations of leaves; to 0.1–2.5 m high. Leptocaul. Helophytic to xerophytic. Leaves minute to small; opposite (or in opposite bundles); decussate; ‘herbaceous’, or leathery; petiolate to sessile; gland-dotted; aromatic; edgewise to the stem, or with ‘normal’ orientation; simple; epulvinate. Leaf blades dorsiventral, or isobilateral, or centric; entire; flat, or solid; terete, or semi-terete, or solid/angular; linear, or lanceolate, or oblong, or ovate; linear, or ovate, or obovate, or oblong, or elliptic; pinnately veined, or parallel-veined, or one-veined; cross-venulate, or without cross-venules. Mature leaf blades adaxially glabrous, or pubescent; abaxially glabrous, or pubescent. 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 conspicuously specialized, or unspecialized.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’ (apparently); axillary; in cymes, or in racemes, or in umbels. Inflorescences simple, or compound. The terminal inflorescence unit cymose. Inflorescences axillary. Flowers pedicellate to sessile; bracteolate (bracteoles 2 or 3). Bracteoles persistent, or deciduous. Flowers minute to medium-sized; regular; 5 merous; cyclic. Free hypanthium present (petals ‘inserted on the calyx’); campanulate, or obconic. Hypogynous disk present. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; polysepalous, or gamosepalous (depending on interpretation). Calyx segments entire. Calyx imbricate, or valvate; exceeded by the corolla; regular; persistent. Sepals elliptic, or triangular (to semi-circular). Corolla present; 5; 1 -whorled; polypetalous; imbricate; regular; white, or pink, or purple. Petals obovate, or orbicular. Androecial members definite in number, or indefinite in number. Androecium 5–12. Androecial members unbranched. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; all equal, or markedly unequal; free of one another; when ‘definite’, 1 -whorled. Stamens 5–12; attached on the rim of the hypanthium; remaining included (exceeded by petals); isomerous with the perianth to diplostemonous; oppositisepalous; all alternating with the corolla members; erect in bud, or inflexed in bud. Filaments not geniculate. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged, or unappendaged. Gynoecium 2(–3) carpelled. The pistil 2(–3) celled. Gynoecium syncarpous; eu-syncarpous; partly inferior. Ovary plurilocular; 2(–3) locular. Epigynous disk absent. Gynoecium stylate. Styles 1; simple; from a depression at the top of the ovary; apical; hairless. Stigmas 1; capitate. Placentation axile. Ovules 6–12 per locule; ascending; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds angular; non-endospermic; straight-sided, discoid to cuboid; non-arillate. Cotyledons 2. Embryo curved.

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

Etymology. After Abraham Baeck (1713–95), Swedish naturalist and physician, Linnaeus's most intimate friend.