118 R. T. BAKER AND H. G. SMITH. 



botanical characteristic of leaf venation it is very probable that 

 when distilled, pinene will be found to be an important constituent 

 of the oil and that phellandrene will be absent. 



The venation of the leaves belonging to those species next in 

 order is that which characterises the Eucalypts yielding eucalyptol 

 oils. Although tending somewhat towards the venation of that 

 group which give oils containing a predominance of pinene, yet 

 the parallel transverse venation, like that of a feather, which is 

 characteristic of the pinene group is not marked, and the venation 

 and reticulation are exceeding delicate, the spaces between the 

 principal veins are larger and a picture of the leaf has a much 

 more graceful and delicate appearance. If we examine the photo- 

 graphs of the leaves of E. Smithii, of E. globulus, of E. longifolia, 

 of E. goniocalyx, or of any other allied species which gives a first 

 class eucalyptol oil, it will be seen that a great similarity of 

 venation exists between them. The general appearance of the 

 venation of these leaves, however, shows greater affinity to those 

 species belonging to the pinene group than to those species having 

 the venation characteristic of the phellandrene-peppermint group, 

 and thus suggests a closer relationship to the pinene oil group. 



It has long been known that pinene was a constant constituent 

 in the oil of those Eucalypts rich in eucalyptol, and that phellan- 

 drene was generally quite absent. We think that the results we 

 have obtained offer a very good explanation for the occurrence of 

 pinene in these oils, and also suggest a reason for the varying 

 amounts of that constituent in the oils of the various species 

 belonging to this group. 



All the oils obtained from those species whose leaves show this 

 venation are characterised by the presence of pinene and of 

 eucalyptol, the predominance or otherwise of the former influencing 

 of course the amount of the latter, This group may very well be 

 styled the eucalyptol-pinene group. The majority of the oils in 

 this group do not contain phellandrene, but as the species branch 

 off into the peppermint group, this constituent makes its appear- 

 ance in increasing amount, but it is then seen that the principal 



