Australian Flowering Plants. 185 



To this epitome may be added a few notes on the topography 

 and climate of Australia as bearing directly on the development 

 of the local flora. 



In the Lower Cretaceous the sea transgressed a portion of 

 central Australia. 



The Upper Cretaceous sea covered nearly the whole of the 

 central portion of Australia and it is probable that this epi- 

 continental sea extended from the Malayan area in the north 

 to the Southern Ocean on the south. 



The Eocene sea was not large and was confined to small 

 areas in the north and south of the continent. Indeed the 

 continent as a whole appears to have been growing in size 

 subsequently to the close of the Cretaceous although a very 

 recent submergence, post-dating the Glacial Periods, appears 

 to have isolated New Guinea and Tasmania from the mainland. 



The land history of Australia in Cretaceous and post-Cre- 

 taceous times is full of interest and throws a considerable 

 amount of light on biological problems. It is as if there has 

 been a general tendency in Australasia and New Zealand to 

 move in a vertical direction in post-Cretaceous time, the move- 

 ment being subject to two great laws, namely: — 



First.- — That elevation, or vertical movement, of the land 

 was emphasized in an easterly direction, due allowance being 

 made for the lagging behind of the two great and relatively 

 heavy portions, namely, Central Australia and the sub-oceanic 

 mass between Australia and New Zealand. 



Second. — That the uplifts after the widespread peneplana- 

 tion of the Cretaceous Period did not proceed continuously, 

 but were saltatory in their action and, moreover, the periods 

 of time punctuating these uplifts became less as the present 

 time approached, but the amount of individual vertical uplift 

 became greater as the periods separating the uplifts became 

 less in duration. This has given rise to great "valley-in-valley" 

 structures owing to the interrupted work of the streams. 



Thus during the Cretaceous Period great peneplains were 1 

 formed and only the hardest rock structures remained to show 

 the existence of former plateaus or hills. In the various 

 Tertiary divisions of time the streams carved valleys with 

 widths so great as to appear as local peneplains, nevertheless 

 they are only very broad shallow valleys, in whose bases other 

 broad and shallow valleys have been excavated. The great uplifts 

 of the later Kosciusko Period allowed the streams to form pro- 

 found canyons receding along these older shallow valleys. In 

 other words the main Tertiary land history has consisted of 



