Abstract

Within Boronia Sm. section Valvatae (Benth.) Engl. the B. grandisepala F.Muell. species group is characterised by a calyx as large or larger than the corolla, simple leaves, and multiangular stellate hairs. The group includes B. grandisepala, a related complex of species, and six newly described species: B. amplectens Duretto, B. quadrilata Duretto, B. suberosa Duretto, B. verecunda Duretto, B. viridiflora Duretto and B. xanthastrum Duretto. All taxa are endemic to the Northern Territory. A phenetic analysis using clustering techniques and multidimensional scaling was used to define taxa within the B. grandisepala species complex. Four taxa were recognised in the complex and three, B. grandisepala subsp. acanthophida Duretto, B. laxa Duretto, and B. prolixa Duretto, are described here. Boronia grandisepala is lectotypified. A key to the species is provided. High levels of diversity and endemism in the flora of the western portion of the Arnhem Land plateau are discussed.