Shrubs or undershrubs, rarely trees. Leaves opposite, rarely in whorls of 3. Flowers appearing axillary, subtended by leaves or leaf-like bracts, or in racemose or paniculate inflorescences subtended by reduced bracts; bracteoles 2. Calyx 2-lipped; corolla 2-lipped, tube usually expanded in throat; abaxial lip consisting of a median lobe which is usually spreading, emarginate or 2-lobed, and 2 lateral lobes; adaxial lip consisting of a median lobe-pair which is erect, emarginate or 2-lobed; stamens 4, anthers 2-locular, with connective often elongated into an appendage; ovary 4-lobed, style terminal, but inserted between ovary-lobes, stigma 2-fid.
About 100 species, all endemic in Australia.
This genus consists of several species complexes that remain unresolved. Putative natural hybrids occur between several species and most species appear to be capable of hybridizing when in cultivation.