XVI International Botanical Congess

Drude's 1898 classification of the Apiaceae, still the most commonly followed, places the genera Xanthosia, Pentapeltis, Schoenolaena and Actinotus in the subtribe Xanthosiinae within the Hydrocotyleae, based on their shared possession of well-developed, often petaloid calyces. This classification, however, excludes several potential sister genera which share inflorescence, flower and fruit characteristics, but which lack a calyx, whilst accommodating the enigmatic genus Actinotus. Morphological homology hypotheses are reviewed for all candidate genera. A phylogenetic analysis of selected genera from the Xanthosiinae and Hydrocotylinae is presented. The Xanthosiinae sensu Drude is paraphyletic by the exclusion of a number of asepalate genera.