Habit and leaf form. Shrubs. Young stems cylindrical, or tetragonal. Leaves opposite; petiolate; simple. Leaf blades entire; pinnately veined; cross-venulate. Leaves with stipules (leaf-like), or without stipules (the stipules reduced, then represented by a ‘stipular line’ linking the opposing leaf bases). Stipules interpetiolar. Leaf blade margins entire, or serrate, or dentate. Leaf anatomy. Hairs present; glandular hairs present, or absent; complex hairs present. Complex hairs stellate. Stem anatomy. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence many-flowered. Flowers in panicles. The terminal inflorescence unit cymose. Inflorescences panicle often long, sometimes with additional panicles in subterminal leaf axils. Flowers bracteate. Bracts linear. Flowers bracteolate; fragrant; regular; 4 merous; cyclic; tetracyclic. Hypogynous disk small or absent. Perianth with distinct calyx and corolla; 8; 2 -whorled; isomerous. Calyx 4; 1 -whorled; gamosepalous; 4 lobed; hairy (densely hairy outside); imbricate; regular. Corolla 4; 1 -whorled; gamopetalous; 4 lobed; imbricate; with straight or curved tube, often rather slender; regular; yellow to orange (in B. madagascariensis). Androecium 4. Androecial members adnate (epipetalous); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4; isomerous with the perianth; oppositisepalous; all alternating with the corolla members; filantherous, or with sessile anthers (subsessile). Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 2 locular. Gynoecium median. Styles 1; attenuate from the ovary; apical. Stigmas 1; 1 - lobed; clavate (or conic). Placentation axile. Ovules 20–50 per locule (or more); pendulous, or ascending; hemianatropous.
Fruit and seed features. Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule (2-valved), or a berry. Capsules loculicidal. Fruit numerous-seeded. Seeds endospermic; winged, or wingless. Cotyledons 2. Embryo straight.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Queensland, New South Wales, and Victoria. South-West Botanical Province.