This Genus was first named Aromadendron by Dr. William Anderson, the surgeon of Captain Cook's second and third expeditions, when collecting with Captain Furneaux in Tasmania, where Hobart now stands. According to Mueller, the first species named was a "Stringybark," now known as E. obliqiia.

The name Eucalyptus was bestowed by L'Heritier in 1788 (Sert. Angl., 18, t. 20), the word being derived from the Greek " well," and ' I cover," in allusion to the operculum or lid which covers the calyx until the stamens are fully developed.

Robert Brown gave the not inappropriate appellation of Eudesmia to the genus in 1814; but, of course, this name is synonymised by the rule of priority.

Still later another name was proposed, i.e., that of Symphyomyrtus, by Schauer, in 1844.

The trees are evergreen, either tall and of enormous height, or dwarfed shrubs, when they are known as "Mallees."

The bark is variable in its nature and texture, being either rough, furrowed, or smooth, features which are more fully described under each bark illustration.

The leaves, as a general rule, are larger on young trees, or adventitious shoots, than on mature trees, whilst in some species they are first opposite and sessile, and then alternate and petiolate. The usual shape is lanceolate, falcate, and, being fixed vertically instead of horizontally, give less shade from the sun's rays than most trees. They also possess the power of twisting on the petiole, probably for the purpose of exposing the thicker cuticle of the leaf to the sun, and thus minimising the volatilisation of oil.

Oil glands are present in the leaves of almost every species, being very pronounced in those of some groups.

The inflorescence is either axillary or terminal.

The flowers have no petals, and the stamens, which with one or two exceptions, are white, inflexed in the bud, and expand when nature removes the operculum.

The fruit consists of a variously enlarged, indurated, truncated calyx tube or capsule, three- to six-celled.

The seeds are small and very numerous, the sterile ones predominating.

The Genus Eucalyptus is of immense importance, whether considered in reference to the timber, essential oils, dyes, perfumes, or kinos. Its trees probably form three-quarters of the whole vegetation of this continent, but the number of species, about 300 odd, can hardly be considered large with such a wide geographical range, the area of Australia being over 3,000,000 square miles.

Systematic Classification here adopted.

WHEW this research was first commenced it was intended to follow the usual morphological systematic classification of previous botanists ; but, as the work progressed, it was found that nothing definite could be arrived at if such a course were followed.

By working on morphological grounds alone, it was found that many of the so-called individual species possessed different barks, timbers, oils, dyes, etc.- a state of things which quite differed from our definition of a species. Such an artificial system (as this research appeared, to prove it) had to be discarded, and what is, apparently, a more real or natural system of classification had to be adopted, viz., founding a species, not on morphological characters of dried material alone, but on -

1. A field knowledge of the trees;

2. The nature and character of their barks;

3. The nature and character of their timbers;

4. Morphology of their fruits, leaves, buds, etc.;

5. Chemical properties and physical characters of the oils, dyes, kinos, etc,

and the utilisation of any other evidence, such as histology, physiology, etc., that might assist in establishing differences or affinities of species.

Our experience, extending now over a period of thirty years, shows that a species founded on the above system as laid down in our first edition is found after these years, to be practically constant in specific characters, however great the range of distribution may be, and many evidences of this fact will be noticed throughout the work. In the very few exceptions to this rule, reasons for the divergence seem to be clear.

Necessarily a classification of species on such a broad basis has not always led us to coincide with the opinions and decisions of previous, as well as contemporaneous, botanical workers on the genus. Our experience verifies the remarks of the late Dr. Woolls, who states :-

"Many of the trees which differ very widely in the texture of their bark and the specific gravity of their wood, and to all intents and purposes are perfectly distinct from each other, yet agree very nearly with ordinary characters by which species are regulated, so that a written description, especially from dried specimens, may be applied to half-a-dozen different kinds of "Gum." Indeed, this has frequently been the case, and even amongst men of scientific attainments, as might be easily shown by referring to the various works which have been written on the subject." (Flora of Aust., p. 213.)

By the method of classification here advocated and adopted, no such confusion of trees is possible.

This research does not in the least favour the uniting of species, and several of those that have been synonymised in the past are here restored to their original specific rank. It was found that the old morphological classification was untenable in particular cases, so also was it recognised that descriptions and original material of some species were made to include, under the one name, trees which were evidently distinct from each other, and these are separated in this work; for instance, under E. Stuartiana, were included in descriptions and original herbarium material of Mueller, the "Victorian Apple," the "But But" of Gippsland, and the "Apple" of New South Wales. These two latter represent the same species, possess distinctive characters from the former, and have been given the name of E. Bridgesiana.

On the same grounds, from E. polvanthciiios, Sch., have been separated E. Fletcheri, Rit.B., E. ovalijolia, R.T.B., and E. Dawsoni, R.T.B., which are all good and distinct species, based on a natural classification. Several similar cases may also be noted in this work.

We have placed little value upon supposed varieties of Eucalypts morphologically determined, because at the best they can only be varieties of varieties, and are thus likely to cause confusion. After all, the difference between a variety and a species is only one of degree, and much must be left to one's judgment as to how far the division or subdivision is advisable.

Whatever differences of opinion may be held in regard to the nomenclature of the species as we now submit them, there can be no doubt as to the particular trees from which the material has been obtained for the research, and this, of course, will be found of the greatest importance both scientifically and economically.

It is evident that the main object of naming the species is for the purpose of recognition, and any simplification in this direction should certainly be considered advantageous.

As the result of this research it can now be stated what are the special yields of oil and their chemical compositions, and because of the practical constancy of constituents in the oils obtained from identical species, it is also now known what the prospective value of such an oil may be, and it can also be stated with some certainty what is its comparative value.

The uniformity of results and the regularity of specific characters has enabled some order to be evolved, which is altogether most satisfactory.

This investigation embraces nearly the whole of the known species in New South Wales, Victoria, Tasmania, and South Australia; a few from Queensland, and about a dozen from Western Australia. It will thus be seen that the oils of most of those species peculiar to the north and north-western portion of the continent yet remain to be determined.

The botanical systematic portion of this work, the figures and other data illustrating the species, are given because of the importance to be attached to the combined botanical and chemical results, thus leading to a more accurate foundation or scientific basis, upon which to establish this important essential oil industry.

The investigation of vegetable products on more than the botanical side is becoming characteristic now of workers in many parts of the world, and we think, that future work on the economics of the Australian flora, should be also conducted by the united efforts of botanist, chemist, physicist, and other workers in cognate sciences, for thus only can be attained a complete knowledge of any plant and its products. One sees the same line of action being pursued to-day in other fields of natural science, for instance the co-ordination of physics and chemistry, with the result that physical chemistry has ultimately emerged as a definite branch of natural knowledge, and similar instances will readily occur to the reader.

Botanical material of all the species from which oil has been extracted is preserved for future reference, should any doubt arise as to the specific origin of any of the essential oils.