During the extensive period thus represented, the species have materially 

 differentiated from the parent stock, and have so well established theii 

 individuality that the evidences here published show bul .1 few species iindei 

 going varietal evolution at the presenl tim rhal there are variations cannol be 

 denied, but the) are comparatively few when the extensive range oi the genus 

 onsidered. With the exception ol about halJ .1 dozen, all the Eu< dypts 

 enumerated in this work will be found to possess comparatively 

 characters throughout their geographical distribution. On the whole, therefore, 

 we think the Eucalypts may be regarded as fairl) invariable. It must, of 

 course, be admitted that herbarium material ot Eucalyptus species can be so 

 arranged as to show peri d gradations; but then all al charai 



are ignored. 



hurt Iht, it is found that the constituents occurring in the oils ot all those 

 species about which there is no difference ot opinion arc always in agreement, 

 and only differ in amount within the limits experienced with the oils ot all the 

 species at varying times oi the year; it may also be that this rule applies to all 

 those species about which little has been previously known. Several instances 

 ot this constanc) ot 1 onstituents will he found under the respective species in this 

 work. 



The late Baron von Mueller, who had a most extensive knowledge ot the 

 Eucalypts ot Australia, recognised the assistance that might be rendered to the 

 botanist in the discrimination of the different species In the chemical investi- 

 gation of thrir several products. The following reference is from his " Eucalypto 

 graphia," Decade 111, article Eucalyptus piperita, published in 1879 : " E. obln/ua 



is distinguished from E. piperita by and perhaps bj anatomic, 



histologic, and ch mica! peculiarities of the hark and wood, which characteristics 

 remain yet more comprehensively to be studied." 



Since the time the above was written much has been done in determining 

 the chemical characteristics ot many of the species, and the results are ot so 

 satisfactory a nature in this connection, that it must be apparent that no investi- 

 gation of the Eucalypts over am one portion ot the continent can he considered 

 complete or conclusive, without it embraces also the chemical investigation of 

 their several products, and other physical characters. This i> well illustrated 

 by the several species that have previously been classified under the name ol 

 E. amygdalina. 



In a paper by Dr. Gladstone on Essential (his {Journ. Chem. Sue, 1864, 



the oil oi Eucalyptus amygdalina is stated to have a specific gravity of 

 0*88l2 at 15-5 ('., a rotation for a column having a length ot to inches, ot 

 1 ;'. . or corrected for optical rotation </„ ,V>'54 ■ ;ui1 ' refractive index for 

 d = 1 -47SS. From what is shown in this work under /•.. phellandra, there seems 

 little doubt but thai this particular sample of oil was obtained from /:'. <// If 



these figures are compared with those for this species distilled recently, it will 

 be -cen how closel) they agree, so that the constancy ot the products obtainable 

 from this species oi Eucalyptus is thus indicated. 



The specifii rotations given 1>\ Mr. W. Percy Wilkinson (Proc. Roy. Soc, 

 Victoria, Vol. VI, |>. 197), lor various samples of supposed E. amygdalina oils, 

 varying from 88-9 to [6-3 . show, when compared with our results, 

 that these samples ot oil had been obtained from more than one species. 

 The specific gravities given in the paper also suggest the same conclusion. This 

 grouping of the species on a morphological basis illustrates the difficulties under 

 which Mr. Wilkinson laboured in his commendable attempt at that time to 

 extend our kriowledge of Eucalyptus oils. 



