378 



First Edition, Plate 9. Second Edition, Plate II. 



Leaf of Eucalyptus dives Schau. 

 The venation indicates the presence of phellandrene in the oil. together with the 

 Peppermint ketone. Note the characteristic looping arrangement of the principal veins, 

 the commencement of which feature is first seen in the bending of the marginal vein in 

 the venation of the leaves belonging to the Encalyptol-(cineol in 2nd Edition)pinene 

 Group. 



Oils obtained from Eucalyptus species having this leaf venation are now exten- 

 sively used for the separation of metallic sulphides by a flotation process. 



[The secondary veins (according to the photo.) make an angle of 15 degrees with 

 the midrib.] 



Correlation of the leaf-venation and chemical constituents of the oils. 



The work of Messrs. Baker and Smith does not either in the 1st (1902) or 2nd 

 Edition (1920) of their " Research on the Eucalypts " refer to correlation in so many 

 words; the word " correlation " is used by them for the first time so far as I know in 

 a paper — " The botanical and chemical character of the Eucalypts and their correlation " 

 contributed to a symposium (British Association, 1915). At the same time, the 

 commencement of this work is their 1901 paper already abstracted, entitled " On the 

 relation between leaf-venation and the presence of certain chemical constituents in the 

 oils of the Eucalypts." 



Let us examine what this correlation is stated to be. 



The 1901 paper (see p. 367) makes three groups : — 



1. The Bloodwoods (corymbosa, intermedia, eximia, irachyphloia, terminalis); 

 Swamp Mahoganies (botryoides, robusta), Blue Gum (saligna), Moreton Bay (lessellaris), 

 " and a few others.'' 



They contain a preponderance of pinene. 



2. " Although tending somewhat towards the venation of that group which 

 gives 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 . . ." 

 They cite Smithii, globulus, longifolia, goniocalyx, " or of any other allied species which 

 gives a first-class Eucalyptol oil." Some other species are mentioned incidentally in 

 the paper. 



3. " All those species whose oils contain phellandrene and the ketone of pepper- 

 mint taste and colour.'' 



The species cited are inriacea, Sieberiana, vitrea, dives, radiata, amygdalina, 

 elegnh nsis. oreadeS ) and many others. 



