PRESIDENTIAL ADDRESS. 39 



between the horizontal and vertical forms, and in a col- 

 lection of leaves some of the foliage may be noticed with 

 the underside pale which proves the horizontal disposition 

 of the leaf. 



Judging by results, it would seem to have been almost a 

 necessity at some particular stage of Eucalyptus develop- 

 ment that some adjustment of leaf arrangement should 

 have been made to conform to some altered climatic con- 

 dition, and ensure the further progress of the genus. The 

 simplest method for those species to adopt which had 

 already developed petiolate leaves, was to gradually twist 

 the leafstalk and so change the position of the blade from 

 horizontal to vertical. It is instructive to enquire into 

 the condition of one or two species which appear to have 

 been unable to do this. 



One of the most interesting Eucalypts in this connection 

 is E. pulverulenta (E. pulvigera) which is growing in the 

 Mountain Region at Cox's River, at Bathurst and near 

 Cooma. This tree appears to have been unable to develop 

 any lanceolate leaves at all, or to substitute the alternate 

 for the juvenile opposite arrangement, the whole of its 

 foliage being either orbicular or broadly ovate, and being 

 sessile, the cordate leaves remain clasping the stem at 

 right angles, and therefore present their full surface to the 

 sun. It is now that we see the potentialities of the 

 Eucalypt to adapt itself to its surroundings, and the method 

 selected in this instance has beeu to cover the leaves with 

 a glaucous powder or vegetable wax which reduces the 

 effect of the sun's rays and therefore lessens the evapor- 

 ation, while it also serves to keep out the cold in winter. 

 It would seem however, that this provision has not been so 

 successful as the twisting of the leaf-stalk, for this species 

 is a weakling and rarely seems able to grow more than 20 

 feet high, and although in the past it appears to have had 



