(c) Venation. — Messrs. Baker and Smith, in Proc. Boy. Soc. of N.S.W., 1901, 

 have grouped certain Eucalyptus leaves into sections in regard to the disposition of 

 their veins, pointing out that the oil-content of the leaves can in a measure he 

 gauged from the venation. The suggestion is ingenious; hut as the venation is, 

 like other characters, variable within such large limits, the method will only he 

 practically useful in the hands of experts. 



(d) Young stems. — Some eucalypts have marked quadrangular stems, e.g., 

 globulus, Maideni, goniocalyx, quadrangulata, tetragona, and many others ; hut, as 

 a rule, this quadrangular appearance, often well marked at an early stage of growth, 

 passes away as growth proceeds. 



(<?) Essential oil. — The perfume of Eucalyptus leaves is owing to the presence 

 of an oil. It varies in different species in regard to both character and amount. In 

 young it is commonly more abundant than in mature foliage, the high proportion of 

 resinous matter in the former being, however, a drawback to distillation. In some 

 cases the perfume is not easy to define, but the crushing of the fresh or even dried 

 leaves in the warm hand has been used as a diagnostic character for many years. 

 It affords a rough but ready test, which is always available and really valuable in 

 skilled hands. Incidentally it may be mentioned that some few leaves, e.g., 

 corymbosa, contain a substance allied to caoutchouc in their tissues, especially in 

 their young state. 



Some years ago, when Superintendent of Technical Education, I determined 

 to ascertain whether this qualitative test of Eucalyptus odour was capable of leading 

 up to further results. Accordingly I obtained samples of commercial Eucalyptus 

 oils, and also watched their distillation in the country, but found, as a general rule, 

 that the various kinds of leaves were not rigidly kept apart. I therefore resolved, 

 with the advice of Dr. T. L. Bancroft, of Brisbane, and the active co-operation of 

 Mr. Owen Blackett, C.E., of the Technical College, to erect a model still capable of 

 holding large charges of leaves, and to distil only those leaves obtained by my own 

 collector or through agencies which permitted their origin to be precisely checked 

 from a botanical point of view. In this way, and in this way only, could Eucalyptus 

 oils of many species, absolutely true to name, be obtained for research. My transfer 

 to the Botanic Gardens removed me from this domain of botanical technology, and 

 the w r ork thus initiated has been continued and extended by my late assistants, 

 Messrs. Baker and Smith. 



(/) Stomata. — Mueller, in Eucalyptographia, under 1$. pachyphylla and E. 



phosnicea, has classified some of the eucalypts according to the number and 

 distribution of the stomata. lie styles the leaves — 



1. Eypogenous, according to the presence of stomata on the under surface 



only. 



2. Heterogenous, according to their presence on both surfaces, but less numerous 



above thau below. 



