278 SPENCER MOORE [octobek 



have failed when it encountered a region which, except for some fresh- 

 water lakes, interposed no bar to its advance. Moreover, Professor 

 Tate's generalisation is the more unsatisfactory, inasmuch as we know 

 nothing about the tertiary flora of Western Australia. 



The idea that the primitive tertiary flora was an immigrant one, so 

 far as concerns Australia, must therefore be regarded as exceedingly 

 problematical. The wide distribution of that flora seems to show that, 

 no doubt with local variations, all the countries inhabited by it enjoyed 

 an approximately similar climate, and it is surely no extravagant 

 hypothesis that Australia played a commensurate part with other 

 countries in the evolution of the flora. Certain forms were of extra- 

 Australian origin, doubtless ; but we are not justified in assuming that 

 one part of the great area peopled by that curious flora was shut out 

 from the drama of evolution and condemned to be a passive recipient 

 of forms generated elsewhere. 



The key to the problem before us seems to be in the recognition 

 of the fact of there being two main elements in the Australian flora, 

 one xerophilous, the other hygrophilous, and by applying the same 

 classification to fossil floras, and rea-ardino; the bulk of the forms having 

 a typical Australian facies as xerophilous forms ; the disappearance 

 from countries outside Australia of natural orders and genera now 

 confined to or characteristic of it can be accounted for without assum- 

 ing the possession of some natural superiority by one flora over 

 another. Let us take the case of Europe, which, during Miocene and 

 still more during earlier tertiary times, had a climate considerably 

 warmer than it has to-day. Now if, under these circumstances, the 

 country were open and included stretches of desert (and this is pre- 

 cisely the character Mr. Wallace 1 considers it had during the Miocene 

 age), here would be conditions exactly parallel in some parts of 

 Australia, particularly Queensland, to-day. And what do we find 

 there ? In the drier parts typical Australian species flourish, while 

 species of Indo-Malayan facies predominate elsewhere. It is therefore 

 probable that the species of European tertiary floras referred to 

 Australian genera were, for the most part, dwellers in the desert 

 patches, while the moister places were occupied, to a large extent, by 

 forms adapted to the conditions there obtaining. That the climate of 

 Europe gradually changed during tertiary times we know, not only 

 because the floras indicate decreasing warmth until the cold Pliocene 

 age arrived, but because the great upheavals during the mountain- 

 making epochs must undoubtedly have affected, in a marked degree, the 

 near annual temperature of the upraised districts and of the countries 

 in their neighbourhood. The diminution of its temperature would 

 have the effect of rendering Europe better fitted to herbaceous vegeta- 

 tion ; it would, in fact, change it from what I have previously called a 

 dendritic to a herbaceous zone, and thus would be set up a tendency 



1 " Geog. Diet, of Animals," vol. i. p. 117. 



