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



On the RELATION BETWEEN LEAF VENATION and- 

 the PRESENCE of CERTAIN CHEMICAL CON- 

 STITUENTS in the OILS of the EUCALYPTS. 



By R. T. Baker, f.l.s., Curator, and Henry G. Smith, f.c.s., 

 Assistant Curator, Technological Museum, Sydney. 



[Read before the Royal Society of N. S. Wales, October 2, 1901.~] 



One of the results of our research on the Eucalypts of New South 

 Wales, is, that we are able to show that there is a marked agree- 

 ment between the chemical constituents occurring in the oils and 

 the venation of the mature lanceolate leaves of the several species, 

 thus forming the genus into fairly well marked groups. It was 

 not until the investigation of the greater portion of these oils had 

 been completed that this fact began to develope. The direct bear- 

 ing of the leaf venation in the several species of Eucalypts had 

 not previously been demonstrated, although it has been customary 

 to incidently refer to it in the original descriptions. We think 

 that it has now become necessary to more fully describe this 

 venation in the future if accuracy of specific characters is desired. 



The reproduction of the venation can be carried out very well 

 by photography alone, so that it is unnecessary to diminish the 

 accuracy of detail by drawing, If the quite fresh leaves be 

 photographed directly upon the paper, using the leaf as a negative, 

 and placing in strong sunlight, an excellent reproduction of the 

 venation is obtained, and the most delicate reticulation, together 

 with the oil-glands (in those species where they are prominent) is 

 well seen. This detail can be reproduced by well known photo- 

 graphic methods. 



The venation of Eucalyptus leaves that has perhaps the most 

 scientific importance is that which is characteristic of the "Blood 

 woods," viz., E. corymbosa, E. intermedia, E. eximia, E. trachy- 

 phloia and E. terminalis; of the "Swamp Mahoganies" E. botryoides 



