The oil of E. hemiphloia, in the work on " Volatile Oils," by Gildemeister and Hoffmann, published by Messrs. Schimmel & Co., is stated to contain cineol and a large amount of cuminic aldehyde (now shown to be laevo-rotatory aromadendral). Our results showed cineol to be present in good quantity, and aromadendral also. It was from the oil of E. hemiphloia that the aromadendral was prepared for the purpose of research. E. hemiphloia is a well-defined species, and but little error should arise in its determination, consequently results agree.

In this connection it might be well to refer to E. hcemastoma. This species was named by Dr. Smith, in 1797, from trees growing at Sydney, in which neighbourhood it still occurs, so that there is little doubt as to the particular tree referred to by him. But there is one species (now E. Wilkinsoniana, R.T.B.), which was for a long time thought to be a "Stringybark" form of E. hæmastoma. If someone had investigated the oil stated to have been distilled from this species and supplied under the name E. hæmastoma, different results would certainly have been obtained, the oil of E. Wilkinsoniana consisting very largely of lævo-pinene.

The "Red-flowering Ironbark" (Eucalyptus sideroxylon) is a species which extends over a large area of country, so that it was possible to obtain material from localities very widely separated. Throughout this area the morphological characters of the species are practically constant, and the nature of the bark and timber shows no variation in general characters-a remark which is also applicable to the other species enumerated in this work. Leaves were received from Liverpool, near Sydney, in December, 1900; from Condobolin in March, 1901; and from Narrabri in July, 1901. These localities are about 350 miles apart, and if connected would form almost an equilateral triangle. The crude oils were in all three cases practically identical, only differing in the amounts of constituents, as might be expected from trees belonging to identical species, whether growing only a few feet from each other or miles apart. The results here recorded are a good illustration of the constancy of chemical constituents in oils of the same species.

The low ester value, the absence of an excessive amount of volatile aldehydes, together with the large amount of cineol, are characteristic of the oil of this species. Perhaps E. obliqua is even a better illustration of this chemical agreement as can be seen under that species.

Many other instances might be mentioned in which this constancy of chemical constituents is demonstrated, not only from our own results, but also in connection with those obtained by previous observers, although unfortunately, precise data in this connection are often wanting; but those mentioned above are sufficient to show that, when no error has been made in the botanical diagnosis, and no mixing of the leaves has taken place, the chemical results will be unmistakable also.

If it is possible to show that this is so, then the corollary must be that the same species of Eucalyptus will give practically the same oil, and consequently the commercial aspect of the question is placed upon a sure foundation; not only from the commercial side of the question is this important, but this constancy of constituents must be taken into consideration in the diagnosis of doubtful species. Supposed allied forms that do not individually show chemical constituents in close agreement cannot consequently be the same species.

As an instance of how this confusing of species has appealed to other workers on Eucalyptus oils, the remarks of Gildemeister and Hoffmann, in the work above quoted, may be mentioned. Two oils supposed to be from E. dealbata, were under review, and they say, "that it is impossible for it" (the second sample) "to have come from the same plant" (as the first sample).

We have received much help towards settling doubtful botanical points since the discovery of this constancy in chemical constituents was made, the results assisting much towards demonstrating differences between the several species, which, otherwise, could not have been decided so satisfactorily. When these differences Have been detected, further research has shown well-marked morphological characters to be also present-in fact, so distinct that the species cannot again be confounded with others; or, in other words, we have learned its history and found its place in nature. The exceptions to this are very rare.

As a further evidence of the comparative constancy of Eucalyptus species, one need only look to their introduction into other countries, where they retain all their physical characters and morphology, as obtains in their native habitat.

The theory has often been advanced that the chemical constituents of the same species vary in different localities, but this idea is not verified by out experiences as regards the Eucalypts, as they do not show those differences in chemical constituents that might perhaps be expected from differences of soils or localities. The reverse may possibly be accounted for by the natural selective, ecological peculiarities shown in many instances by the species themselves, as it is remarkable how a certain species will flourish on a particular geological formation and become singular to like formations, while at the same time objecting to those entirely different. However that may be, those influences do not appear to act detrimentally, or to interfere in any way with the practical constancy of results.