PRESIDENTIAL ADDRESS. 55 



constituent in what are regarded as the earliest forms of 

 Eucalypts now remaining, that constituent is likely to 

 occur in some varying quantity throughout the slowly 

 evolving genus. 



In seeking for some relationship between essential oils 

 and geological formations, it is found that those Eucalypts 

 typical of the class which produce pinene oils, prefer silice- 

 ous to basic formations, and select those of the former 

 where much of the silica is in a free state. 



Eucalyptol. — The species which contain a large propor- 

 tion of eucalyptol (cineol), appear to comprise the bulk of 

 the genus, and so far as New South Wales is concerned, 

 occur most in the Coastal Area and Interior as well as 

 lower Mountain Region, and are found least in the coldest 

 parts, E. amygdalina being an exception. This appears to 

 be the dominant constituent of the genus at the present 

 day, and as it appears to mark a transition from pinene of 

 the warm, to phellandrene of the cold climate, it should be 

 expected to diminish in quantity, even in the same species, 

 as an ascent is made into the colder altitudes. Eucalyptol- 

 yielding species usually occur on geological formations 

 varying from basic to fairly acid, and even occasionally 

 on very siliceous rocks, but of the three oil-yielding groups 

 this is perhaps the most typical of the basic formation and 

 may be found on the black soils of the Interior. 



Phellandrene. — The home of this constituent in its 

 greatest volume is in the Mountain Region, and in a 

 reducing quantity it occurs in the Coastal Area, Western 

 Slopes and the Interior, being rare in the last named 

 division. In none of these schemes of distribution is any 

 particular character or quality found to be confined pre- 

 cisely within any exact limits, nor is such a condition of 

 grouping to be expected in an evolving genus, but in out- 

 lining their distribution, characters are regarded as typical 



