48 R. H. CAMBAGE. 



the Coastal Area ; and so far as New South Wales is con- 

 cerned, is practically confined to those two divisions, the 

 form being absent from the Western Slopes and the Interior. 

 E. coriacea and stellulata are very pronounced examples 

 of this class of venation. 



A study of the distribution of this type of leaf in New 

 South Wales, Victoria, and Tasmania, leads to the conclusion 

 that it has been evolved largely if not wholly in response 

 to cool and moist conditions, and it is of interest to note 

 that the Eucalypt which ascends higher than any other in 

 Australia, viz.: — E. coriacea, and which reaches an altitude 

 of 6,500 feet, is one of the most typical of the parallel 

 veined forms in the genus. Everything seems to point to 

 the conclusion that the parallel veined leaf is the newest 

 type of Eucalyptus leaf in existence, that it was developed 

 in the south as an offshoot from the oblique venation, and 

 after the Kosciusko uplift, migrated north along the resul- 

 tant Main Divide throughout the entire length of New 

 South Wales. 



Geological formations selected by Eucalypts tvith vari- 

 ous leaf venations. — Species having the various types of 

 leaf venation appear to exercise some preference for differ- 

 ent classes of geological formations. Those having the 

 transverse venation generally select the acid rocks which 

 are composed of upwards of 70% silica, much of which is in 

 a free state. Species with the oblique venation are more 

 typical of the basic rocks and soils, although by no means 

 confined to that formation, some even growing on highly 

 siliceous rocks. The trees with the parallel veins, such as 

 E. dives, occupy chiefly the fairly siliceous formations or 

 those containing between 60 and 70% silica, but some of 

 them grow on basic formations, while dthers are on highly 



siliceous. 



Fossil Leaves. 



Of the fossil leaves which have been identified as 



Eucalypts in Miocene deposits in South Eastern Australia, 



