PRESIDENTIAL ADDRESS. 57 



developing, possibly ever since late Cretaceous time, it is 

 to be expected that a considerable overlapping of evolu- 

 tionary characters exists, and such being found to be the 

 case, this tends to render the forming of definite conclusions 

 more difficult. 



The available evidence points to the conclusion that the 

 Eucalypts either invaded, or probably originated in the 

 northern or warm, rather than the southern or cold portion 

 of Australia. The anthers belonged to the section known 

 as parallelantherae, the leaves had the transverse venation, 

 and the chief constituent of the essential oils was pinene. 

 The type of Eucalypt containing the transverse venation 

 is absent from Tasmania, and in latitudes south of about 

 35° is confined to a comparatively narrow coastal strip in 

 New South. Wales and Victoria. As the genus evolved, its 

 characters continued to be modified in response to its 

 surroundings, largely it would seem through its invasion of 

 colder latitudes, and later by its ascent to greater eleva- 

 tions produced by earth movements along Eastern Australia 

 and probably from other causes not yet understood, amongst 

 which are likely to be its selection of different plant foods 

 owing to the class of geological formation which supported 

 its growth, and the amount of moisture present. A trans- 

 ition began to appear from the parallelantherae towards 

 the porantherse, a somewhat small section which avoids 

 the cold regions, and also in an opposite manner towards 

 the renantherse, a section which shuns hot and dry con- 

 ditions, but favours the cold and moist. The transverse 

 venation was also largely superseded by the oblique or 

 diagonal venation, and eucalyptol (cineol) became an 

 important constituent of the essential oil in the leaves. 



At the present day the home of the typical renantherse 

 is largely in the cool and moist regions, and with it may 

 be found the majority of those species whose leaves have 



