PRESIDENTIAL ADDRESS. 53 



It is pointed out that the Eucalypts which belong to 

 the porantherae section rather favour the basic than the 

 siliceous formations, and it seems not improbable that an 

 extended study of that phase of development which results 

 from response to certain plant food, may largely help to 

 elucidate some of the mysteries of evolution in the genus. 



Renantherce. — Turning now to the renantherae, we find 

 that it is practically confined to South Eastern Australia, 

 and is the principal form occurring in the higher Mountain 

 Region, and also that nearly all those Eucalypts haviog 

 leaves with the parallel venation possess the kidney-shaped 

 anther. Next to the mountains it is most common in the 

 Coastal Area, but on the drier Western Slopes is rare 

 indeed, while in the still drier Interior of New South Wales 

 this form of anther does not occur at all. 



Considering this general distribution of the last named 

 two types of anther, there seem reasonable grounds for 

 assuming that one necessary condition for the development 

 of the former is warmth, while the latter is largely the 

 result of moist and cool surroundings. 



There are anomalous members of the section renantherae, 

 which in an evolving genus is not a matter for surprise, 

 examples being found in such species as E. Smithli and 

 microcorys. 



When writing of E. pauci flora (coriacea) in the Eucalyp- 

 tographia, Baron von Mueller refers to the relationship 

 which exists between the renantherae type of anther and 

 the leaves with parallel venation. 



Essential Oils. 

 In their " Research on the Eucalypts," Messrs Baker 

 and Smith record that three of the important constituents 

 of the essential oils obtained from the leaves are : — pinene, 

 eucalyptol (cineol) and phellandrene. At least one of these 

 constituents has been obtained from almost every Eucalypt 



