24 R. H. CAMBAGE. 



distinct forms of nutriment, should exercise some important 

 influence in the evolution of species. 



Climate. — Undoubtedly the dominating influence in regu- 

 lating the distribution of any flora over a large area, is 

 climatic, and this in itself is determined by the latitude, 

 elevation, rainfall and aspect. The whole of the Eucalypts 

 in Australia and Tasmania occur approximately between 

 the latitudes of 11° and 44°, while those on the mainland of 

 Australia extend from about the latitude of 11° to 39°. So 

 far, therefore, as the mainland is concerned, if we can in 

 imagination reconstruct it as a peneplain only a few hundred 

 feet above sea level, as geologists believe was the case in 

 early Tertiary, we can see that the climate under present 

 day conditions would have been a mild to a warm one. We 

 have evidence from the remains found of large, somewhat 

 unweildy, animals such as the Diprotodon, which from their 

 structure must have lived on level marshy country, that 

 the climate was then a fairly damp one. It is well also to 

 remember that at this early period Tasmania formed part 

 of the mainland. From available evidence it would appear 

 that Eucalypts north of latitude 35°, which to day are 

 restricted to elevations above 2,000 feet, could have had 

 no existence in New South Wales north of that latitude, in 

 their present form, under Eocene and perhaps Miocene 

 conditions. Examples of such Eucalypts are supplied in 

 E. coriacea, stellulata, dives, vitrea, and amygdalina. 



The final uplift towards the close of the Tertiary, the 

 Kosciusko Epoch, changed all this. The resultant Main 

 Divide not only separated the original uniform climate into 

 three, but with its fairly steep eastern face presented to 

 the ocean, it created moister conditions over the coastal 

 area, and with its mountain elevations, which reach up to 

 7,300 feet, it provided the cool conditions necessary for the 

 growth of Eucalypts which previously may not have existed 



