441 
The taxonomy of Xanthosia huegelii and closely 
related species (Apiaceae: Hydrocotyloideae) 
J.M. Hart 
Abstract 
J.M. Hart (John Ray Herbarium, School of Biological Sciences, Macleay Building M2, The University of 
Sydney, NSW 2006, Australia; e-mail: jmh@bio.usyd.edu.au). 2000. The taxonomy o/Xanthosia huegelii 
and closely related species (Apiaceae: Hydrocotyloideae). Telopea 8(4): 441-453. Recognition of the three 
species Xanthosia huegelii, X. pusilla and X. tasmanica has been inconsistent across their distribution 
in southern Australia. As part of a revision of the genus, the history of this group of species is 
reviewed and the position of the competing names clarified. Examination of the morphology of 
the species, both from living and herbarium material, resulted in only two taxa being recognised, 
X. huegelii and X. tasmanica. Both species are more widely distributed than previously thought, due 
mainly to the misapplication of the name X. pusilla. 
Introduction 
Xanthosia huegelii (Benth.) Steud., X. pusilla Bunge and X. tasmanica Domin are small 
herbaceous species, commonly occurring in eucalypt forest and heath communities in 
southern Australia. These species are distinguished from all other members of the 
genus by their trifoliolate leaves with entire segments. 
In the course of a revision of the genus, the delimitation of the currently recognised 
species was found to be inconsistent. There has been much confusion in distinguishing 
the three species from one another, particularly in the application of the competing 
names X. tasmanica and X. pusilla, considered as distinct taxa in some treatments 
(e.g. Eichler 1986) and a single species, X. pusilla, in others (e.g. Curtis 1963). 
This paper aims to clarify the application of the competing names based on field 
observations and herbarium material, including examination of the relevant type 
specimens. 
Taxonomic history 
Leucolaena huegelii was described by Bentham in 1837 from specimens collected in the 
Swan River and King Georges Sound areas in Western Australia. Bentham described 
the species as having trifoliolate leaves with linear segments, and pedunculate 
compound umbels with 3-5 rays and two flowers in each umbellule. Steudel (1841: 
790-791) transferred the species from the illegitimate genus Leucolaena R. Br. to 
Xanthosia Rudge. 
Bunge (1845) described two new species, X. pusilla and X. glabrata. Xanthosia pusilla 
was described as possessing oblong leaf segments and a sessile, simple umbel with 1-2 
flowers. Xanthosia glabrata was described as a glabrous herb with oblong-linear leaf 
segments and pedunculate simple umbels with 1-3 flowers. Both species were based 
on specimens from Western Australia. 
