284 SPENCER MOORE [october 



also only to consider the hygrophilous element in the two floras, since 

 the Indo-Malayan climate is not suited to xerophilous ones. While, 

 therefore, the considerable areas in Northern and North -Eastern 

 Australia * favourable to hygrophilous species have been open to the 

 incursions of the whole of the rich Indo-Malayan flora, only those 

 Australian forms adapted to hygrophilous have had a chance of 

 penetrating into Indo- Malaya. It is submitted, therefore, that a 

 preponderant migration from the north is only what ought to be 

 expected on the doctrine of chances, and that there is no need to 

 import into the discussion notions as to relative superiority and 

 inferiority. We thus stand here upon precisely the same ground as 

 that taken up in considering the supposed aggressive power of the 

 Scandinavian flora. 



The case is different with the Antarctic element of the Australian 

 flora. This comprises forms suited to the lower grades of temperature, 

 and all available evidence teaches us that colder conditions have been, 

 of course in a geological sense, temporary only in Australia. But 

 bearing in mind that glacial effects must have lasted a very long time, 

 as contrasted with the span of human life, we may suppose that 

 species of which the ancestors were received from the south may have 

 been differentiated within the wide area in Australia suited to Antarctic 

 forms during glacial times and times immediately preceding and 

 following them, and that some at least of such species, accompanied by 

 native ones which had become adapted to colder conditions, would 

 migrate south when glacial conditions passed away, and so add a new, 

 if small, element of Australian origin to the Antarctic flora. In any 

 event, the Antarctic element seems to be an immigrant one. 2 I do not 

 remember any attempt to prove from the presence of Antarctic forms 

 the possession of " aggressive power " by the Antarctic flora, though, 

 as the evidence for migration is so much stronger in this case, the 

 omission, to say the least of it, is somewhat strange. 



But Professor Tate tells us that a flora of exotic origin is in the 

 act of displacing its indigenous vegetation from Central Australia. 

 Let us see upon what evidence this conclusion reposes. Most of the 

 truly Australian forms, he says, 3 usually grow gregariously or in 

 isolated colonies from a few square yards to several square miles in 

 area. But in a country like Australia, where good patches of soil 

 alternate with bad ones, this gregarious habit scarcely implies want of 

 adaptation. I saw precisely the same thing in Western Australia, and 

 the inference I drew from it was directly contrary to Professor Tate's, 

 namely, that the large numbers of a species monopolising or almost 

 monopolising considerable portions of ground argued success in their 



1 And to a somewhat more limited extent the North-West too. 



2 Some of the herbaceous genera now characteristic of northern lands represented in 

 Australia may have been introduced from the south during the glacial period. 



3 "Report of the Horn Expedition " (Botauy), p. 120. 



