GREY GUM AND ITS ESSENTIAL OIL. 263 
The time has arrived when it is imperative that the percentage 
of eucalyptol in an oil must be of the highest. It is usually con- 
sidered that the therapeutically active agent of eucalyptus oil is 
eucalyptol, and commercially eucalyptol is the constituent required, 
and the value of eucalyptus oil is determined on the amount of 
that body present. Besides, the demand for pure eucalyptol is 
increasing considerably, and everything points to the fact that 
the inferior eucalyptus oils, or those consisting principally of 
terpenes, will become less and less in demand where the oils are 
' judged on scientific principles and in an open market. We hope 
that the distillation of these inferior oils for medicinal purposes 
will cease. By these researches we hope to be able to direct 
attention to those trees from which good oils can be obtained, 
and to point out those species that are to be avoided. 
We think that this is the first attempt to obtain an oil from 
the leaves of the “grey gum,” E. pwnctata. It is perhaps 
remarkable that this species should have escaped so long, but 
although much has been done in regard to the oil obtained from 
some of the eucalypts, #. globulus, FE. amygdalina, etc., yet, but 
comparatively few species have been touched. Our researches 
justify us in stating that other trees besides #. punctata will 
prove of value as oil yielders. The yield of oil is good, but we 
have made no attempt to treat leaves only, but have taken the 
leaves with terminal branchlets, as described in our previous 
paper on £. piperita. 
The amount of work that has been undertaken in the investiga- 
tion of the essential oils obtained from the eucalypts is very great, 
and the literature on the subject is enormous. Mr. J. H. Maiden, 
F.L.8., has brought together references to most of this in his 
Bibliography of Economic Botany,! so that it will be unnecessary 
for us to reproduce it here. The severe remarks often made 
respecting eucalyptus oils should be seriously considered. Schimmel 
and Co., in their semi-annual reports, write strongly on this 
1 Government Printer, Sydney, 1892. 
