; r 
a? 
24 H. G. SMITH. 
conditions of soil and climate in the same way that 
Hucalyptus had, and this is illustrated by the fact that the 
leaf oils of the Angophoras are all practically identical in 
composition, while the exudations of the species are also 
similar. The principal terpene in these oils is pinene, and 
this has an identical specific rotation in all the species, a 
constancy so very different from that found in Eucalyptus. 
The ester is geranyl-acetate and this also occurs in very 
many species of Hucalyptus, reaching a maximum in H, 
Macarthuri. | 
These results taken together seem to indicate that the 
constituents of the oils of the earlier members of the genus 
Eucalyptus had their origin in those of the genus Angophora 
if not in a still older one. 
From the Corymbosece group the genus Eucalyptus 
evolved in various directions, and to enable the conditions 
adverse to distribution to be overcome, both the botanical 
features and chemical characters underwent considerable 
changes. The mature lanceolate leaves altered consider- 
ably the disposition of their veins, denoting eventually the 
presence of eucalyptol (cineol) in their oils, or of that of 
the terpene phellandrene in those of the more recent species. 
The form and structure of their anthers and of their seed- 
lings changed in agreement. The appearance of their 
barks became more diverse, and distinct groups were 
established considered on a cortical classification; while 
the texture, hardness and general characters of the woods 
of the several groups varied considerably. The tannins 
and astringent exudations are also shown to have been 
correspondingly under the influences of the factors which 
were instrumental in bringing about changes in the genus; 
constituents characteristic of the exudations of earlier 
members continue for a time and then are found no more, 
while even the tannin in the members of the later STOUps 
is not the same substance as that in the earlier. 
