The comparative constancy of specific characters, morphological and chemical, such as the constituents of the oils, dyes, tans, etc, amongst the

Eucalypts is perhaps only what one might expect to find, when it is assumed that this continent is one of, if not, the oldest on this planet, having evidently remained stationary during certain subsidences and upheavals of other parts of the earth, and so preserved the fauna and Mora of past geological times.

During the extensive period thus represented, the species have materially differentiated from the parent stock, and have so well established their individuality that the evidences here published show but a few species undergoing varietal evolution at the present time. That there are variations cannot be denied, but they are comparatively few when the extensive range of the genus is considered. With the exception of about half a dozen, all the Eucalypts enumerated in this work will be found to possess comparatively constant characters throughout their geographical distribution. On the whole, therefore, we think the Eucalypts may be regarded as fairly invariable. It must, of course, be admitted that herbarium material of Eucalyptus species can be so arranged as to show perfect gradations; but then all other physical characters are ignored.

Further, it is found that the constituents occurring in the oils of all those species about which there is no difference of opinion are always in agreement, and only differ in amount within the limits experienced with the oils of all the species at varying times of the year; it may also be that this rule applies to all those species about which little has been previously known. Several instances of this constancy of constituents will be found under the respective species in this work.

The late Baron von Mueller, who had a most extensive knowledge of the Eucalypts of Australia, recognised the assistance that might be rendered to the botanist in the discrimination of the different species by the chemical investigation of their several products. The following reference is from his "Eucalypto-graphia," Decade III, article Eucalyptus piperita, published in 1879 : "E. oblit/ua is distinguished from E. piperita by.....and perhaps by anatomic, histologic, and chemical peculiarities of the bark 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 of many of the species, and the results are of so satisfactory a nature in this connection, that it must be apparent that no investigation of the Eucalypts over any one portion of the continent can be considered complete or conclusive, without it embraces also the chemical investigation of their several products, and other physical characters. This is well illustrated by the several species that have previously been classified under the name of E. amygdalina.

In a paper by Dr. Gladstone on Essential Oils (Journ. Chem. Soc, 1864, p. 3), the oil of Eucalyptus amygdalina is stated to have a specific gravity of 0.8812 at 15.5° C., a rotation for a column having a length of 10 inches, of - 1360, or corrected for optical rotation aD - 53.54°, and refractive index for D= 1.4788. From what is shown in this work under E. phellandra, there seems little doubt but that this particular sample of oil was obtained from E. dives. If these figures are compared with those for this species distilled recently, it will be seen how closely they agree, so that the constancy of the products obtainable from this species of Eucalyptus is thus indicated.

The specific rotations given by Mr. \Y. Percy Wilkinson (Proc. Roy. Soc, Victoria, Vol. VI, p. 197), for various samples of supposed E. amygdalina oils, varying from -88.9° to -16.3°, show, when compared with our results, that these samples of 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 knowledge of Eucalyptus oils.

The differences in results recorded for the oil of E. amygdalina in various works on " Essential Oils " can be accounted for in the same way, and this is probably so in all cases where the oil of E. amygdalina is recorded as showing great variability.

It only requires to be mentioned that the constituents of the oil of E. globulus are practically constant from whatever locality the material is obtained, and the sample of oil from this species that we distilled from material collected at Jenolan, New South Wales, differed in no respect from the product of trees growing in Tasmania, or in Victoria. M. Voiry, in his paper, Gompt. Rendus, 1888, p. 1419, also expresses this constancy in the following paragraph: -"Cette propriete est commune a tous les echantillons d'essence d'Eucalyptus globulus de differentes provenances que j'ai pu examiner .

Messrs. Faulding & Co., of Adelaide, in 1901, kindly supplied us with the crude oil of E. cneorijolia. The oil of this species is usually laevo-rotatory, the laevo-rotation being caused by the aldehyde aromadendral; and not by phellan-drene, as that terpene does not occur in this oil. The oil had a rotation in a 100-mm. tube, for the crude oil, of -5.4°; that of the rectified oil being -3.0°; the specific gravity of the crude oil was 0.9287 at 15o C. An analysis made in 1891 by Mr. Robert H. Davies, of Apothecaries Hall, London, of the oil of E. cneorijolia for Messrs. W. dimming & Co., Adelaide, showed the sample to have a rotation in a-100-mm. tube of -3.53°, and a specific gravity at 6o° F. of 0.923.

A recent analysis of the oil of this species published in this work, also shows concordant results, so that with this species there is a remarkable agreement also, particularly as this is one of the heavy Eucalyptus oils.