This section is from the book "A Research On The Eucalypts Especially In Regard To Their Essential Oils", by Richard T. Baker, Henry G. Smith. Also available from Amazon: A Research On The Eucalypts And Their Essential Oils.
The scheme of evolution of the Eucalypts formulated in the following article is further supported by following out the geographical distribution of the species.
Thus on the assumption that those Eucalypts known as the "Bloodwoods" and their affinities are the oldest group of these trees, and that Western Australia is the oldest portion of the continent, one would naturally expect to find them well represented in that part of the continent, and such is the case. The " Bloodwoods," and red-timbered Eucalypts especially, are the distinguishing features of the forest trees belonging to the Genus in Western and North-western Australia, and trees with these characters extend through the Northern Territory down Eastern Queensland, and Eastern New South Wales, discontinuing in the north-east corner of Victoria, there being no representative of this group in Tasmania, where only pale coloured timbers occur.
The closely allied Genus Angophora accompanies the red-timbered Eucalypts in Queensland, down through New South Wales, finishing with one species, Angophora intermedia, on the Grampians, in Victoria. No Angophora species has been recorded from Tasmania, and no red wood Eucalyptus, either, for the matter of that - a pale timber feature that extends well into Victoria. Pale-coloured timbers also extend north, far into New South Wales. In this latter State we find in addition to the red woods, the groups of "Peppermints," "Stringybarks," and "Gums," gradually increase in number and importance as one travels south to Victoria, until in Tasmania they are the only representatives of the genus-the red woods and "Bloodwoods" being quite absent.
Branching off at different intervals from the main line of species are the "Ironbarks," "Gums," "Boxes," "Mallees," "Stringybarks," and "Peppermints." The "Ironbarks" are an interesting group, and evidently are closely connected with the members which yield oils richest in cineol.
Not only do we thus find an evolutionary agreement with the geology and botany, but this is further confirmed by the chemistry, for according to the above reasoning the more recent of the species shown at the end of our table, are found to yield phellandrene-bearing oils, while with the most ancient species occurring at the beginning of the table the terpene is pinene.
Thus applying the table of evolution to a contour map of Australia in the order of geological age, the head or primary species (the red woods) are found in the western portion of the continent, and then travelling north and south, complete the range with the pale-coloured timbers in Tasmania and Southern Victoria.