A reappraisal of Ptilotus aristatus and P. blackii (Amaranthaceae)

The taxonomy of Ptilotus aristatus Benl and the related P. blackii Benl is revised and their relationship to one another clarified. Ptilotus aristatus is here treated as comprising two subspecies, P. aristatus subsp. aristatus and P. aristatus subsp. micranthus Albr. & Lally, nom. et stat. nov. Ptilotus aristatus var. eichlerianus (Benl) Benl is synonymised under P. aristatus subsp. aristatus, and P. aristatus var. exilis Benl and P. aristatus var. stenophyllus Benl are synonymised under P. aristatus subsp. micranthus Albr. & Lally. The original circumscription of P. blackii is shown to be a mixed concept (including P. aristatus subsp. aristatus), and this taxon is redescribed. Keys to P. blackii and P. aristatus, and to the subspecies of P. aristatus are provided. Distribution maps of all recognised taxa are presented. Key word: Amaranthaceae, Ptilotus, taxonomy, nomenclature.