190 THE BUILDING OF EASTERN AUSTRALIA 



with the casuarinae, but the others are almost certainljr 

 invaders from the west. 



The plants which they drove back were largely lauracese,, 

 as is well demonstrated by the fossil leaves of the older 

 deep leads and the trachytic tuffs of the Warrumbungles. 



The grasses now dominant in Eastern Australia pro- 

 bably also originated in the west, especially those of the 

 interior. 



The wet climate of the Middle Tertiary drove the arid 

 climate plants, which had established themselves over 

 the raised Cretaceous basin, into the Eastern coastal regions, 

 while tuft grasses, similar to those of the Plains of Promise^ 

 took possession of the drier parts of the interior. 



The re-elevation of the coastal rim, with the restoration 

 of arid conditions on the inland plains, brought victory 

 to the saltbush and similar orders, and caused a return 

 to some extent of the eastern flora. 



Messrs. R. H. Cambage, F.L.S., andE. C. Andrews, B.A., 

 F.G.S., are at present carrying on the interesting and im- 

 portant work of tracing the descent of Australian forest- 

 timbers, and investigating what geologic and physio- 

 graphic causes brought about the specific differences now 

 obtaining between the trees of different parts. 



Late Pliocene uplift led to the creation of three climates.. 

 (1) coastal, moist and warm ; (2) tableland, cool and moder^ 

 ately dry ; (3) inland plains, dry and with seasonal 

 extremes of temperature. This movement, according to 

 Cambage and Andrews, caused a differentiation of our 

 trees into three groups. Each genus developed species suited 

 for each of these climatic zones. Pleistocene faulting^ 

 according to the same authors, separated still further 

 members of the same group in such a way that further 

 specific differences arose. In other cases faulting allowed 

 an intermingling of coastal and inland types, as was the case 

 on the Cassilis geocol [33], where the western flora mingles 

 with that typical of the Hunter River Valley. 



The work of Mr. Cambage promises to cast considerable 

 illumination on obscure problems of Tertiary geology, 

 thus he shows, from the distribution of the Casuarinse, 

 that a portion of south-eastern Australia must have been, 

 lost by faulting in post-Tertiary times. 



