85 



Plants of the Lake Eyre Basin. 



By Professor Ralph Tate, F.L.8., F.G.S.^ *i:c. 



In my address delivered before the Biological Section of the 

 Australasian Association for the Advancement of Science at its 

 meeting in August, I occupied myself with the large question of 

 the influence of climatological and geological changes on the 

 distribution of the constituents of the Australian Flora. In it I 

 gave summaries of facts rather than details, and among others 

 those relating to the plants of the Lake Eyre Basin. This flora 

 will have some special interest for us, and I venture to submit to 

 you those particulars of it which are wanting in my address. 



The flora of the Lake Eyre Basin was selected as best illustrat- 

 ing the characteristics of the botanical region which I had named 

 Eremian ; geographically it is only a small section of the region. 

 Lake Eyre is situated nearly in the centre of the continent, and 

 at or a little below sea level. It occupies the centre of the area 

 of normally high barometric pressure, and minimum rainfall in 

 Australia. The annual rainfall on the south and west does not 

 exceed five inches, though it is a little more on the east ; but the 

 whole area is subjected to protracted droughts. The area has 

 passed through extreme climatic vicissitudes, and it offers the very 

 best initial study on the nature and origin of the Eremian flora 

 as a whole. 



The basin is vast, but I restrict myself in this communication 

 to the depressed area around the lake — an area that probably 

 coincides with the former extension of the lacustrine waters (now 

 salt to saturation). The bounding more elevated lands on the 

 south, and the Peake ranges on its north-west, and hence to the 

 MacDonnell Range yield, as far as botanically known, the same 

 type of flora, though richer in genera and to some extent 

 specifically distinct. The floral type, which prevails, extends all 

 over the central region of the continent, from the west of the 

 Cordilleras of Eastern Australia to the western seaboard between 

 the Gascoyne and De Grey rivers. 



Phytographically, this region isolates the Autocldhonian (S.W, 

 Australia) from the Euronotian (S.E. Australia), the dry inter- 

 vening country presenting an effectual barrier to an interchange 

 of species. If, as I suppose, that the Lake Eyre basin, which is 

 now a sandy-saline waste, was once occupied by a vast inland 

 sea of fresh water, of which Lakes Blanche and Frome are out- 

 liers, whilst contemporaneously Lake Torrens and the system of 



