A taxonomic treatment is presented for all Polygala L. species of northern Australia (north of 26°S). In total, 45 species are treated, of which 44 are native and 36 are endemic to Australia. Twenty-six new species and four new varieties are described. A key to all 50 Australian species is provided, including six introduced species (five of which are restricted to southern states of Australia and are not treated here in detail). Lectotypes are here designated for five names. Nomenclatural issues regarding P. linariifolia Willd., P. glaucoides L. and P. triflora L. are discussed.

Stylidium petiolare Sond. and allies (Stylidiaceae) are a group of diminutive triggerplants from southern Western Australia that have evolved small corms capable of significant desiccation during summer dormancy. A taxonomic review of these microgeophytes has identified 14 taxa, of which S. cornuatum Wege, S. scintillans Wege and S. xanthellum Wege are newly described and S. asteroideum F.L.Erickson & J.H.Willis and S. rubricalyx F.L.Erickson & J.H.Willis are reinstated. S. emarginatum subsp. exappendiculatum Lowrie & Carlquist and S. emarginatum subsp. decipiens Carlquist are elevated to species level and their respective distributions significantly expanded following the assessment of herbarium specimens and field survey. Revised descriptions are provided for S. emarginatum Sond., S. insensitivum Carlquist, S. obtusatum Sond., S. periscelianthum F.L.Erickson & J.H.Willis, S. petiolare Sond., S. pulchellum Sond. and S. udusicola Lowrie & Kenneally. S. bolgartense F.L.Erickson & J.H.Willis is retained as a synonym of a broadly defined S. obtusatum, and S. petiolare var. paucifoliatum Sond. is newly placed into synonymy under S. xanthellum. Lectotypes are selected for S. asteroideum, S. emarginatum, S. petiolare, S. petiolare var. paucifoliatum, S. pulchellum and S. obtusatum. S. emarginatum var. macranthum E.Pritz. is newly placed into synonymy under S. emarginatum, with a neotype designated. S. scintillans, discovered during surveys of mining leases in the Yalgoo region, is considered Threatened in Western Australia, whereas S. asteroideum, S. cornuatum, S. exappendiculatum (Lowrie & Carlquist) Wege, S. periscelianthum and S. rubricalyx are all listed as being of conservation concern. Further field survey and collections of the microgeophytic triggerplants are required to refine the taxonomy presented herein and to better understand the distribution and conservation status of these taxa.