LEAF VENATION AND CHEMICAL CONSTITUENTS OF EUCALYPTS. 121 



•evidence. We are now able to demonstrate most fully that of all 

 the numerous peculiarities of the Eucalypts not one is of greater 

 value in indicating differences in the several species or that is 

 more conclusive in its results, than is the practical constancy of 

 chemical constituents in identical species, a fact of the greatest 

 scientific and economic importance. 



It is thus possible to suggest in the majority of instances and 

 ■with some degree of certainty, what the general constituents of an 

 Eucalyptus oil will be, by the simple investigation of the venation 

 of the leaves. By the reverse process, we ought to be able to form 

 a very good idea of any species by the investigation of its products 

 chemically. It has already been stated that a remarkable constancy 

 is found in the chemical constituents of the oil of any particular 

 species wherever grown, even if obtained from material collected 

 irom localities 300 or 400 miles apart. We have numerous instances 

 of this constancy. Some time back we called attention to the fact 

 that the oil obtained from a mallee (a shrubby form of Eucalypt) 

 growing on the Blue Mountains at Lawson, Katoomba, etc., and 

 known as E. stricta was different from that obtained from the 

 supposed E. stricta growing around Berrima and Mittagong, but 

 it was not possible to separate them on any known botanical 

 characters, as no morphological differences could be detected, but 

 the fact remained that the oils were different and always so, 

 because to test this we obtained material from Berrima and 

 Mittagong at different times of the year. The leaves of both 

 species are thick and fleshy, so that the venation is externally 

 quite indistinct, but if the leaves are boiled for some time in a 

 dilute solution of potash and the cuticle on one side of the leaf 

 then removed, it will be seen that E. stricta from Lawson has the 

 venation characteristic of eucalyptol-pinene oils, inclining to the 

 aromadendral group (eucalyptol being the principal constituent 

 of this oil) while the leaves of the species from Berrima has the 

 venation characteristic of E. dives and of the oils belonging to the 

 phellandrene-peppermint group. The peppermint constituent has 

 been found to be a constant constituent of the oil of this Eucalypt, 



