INTRODUCTORY ESSAY. iii 
variety in its Flora; of the differences in the vegetation of its several parts; and of the peculiarity 
both of its Fauna and Flora, as compared with those of other countries. I accordingly prepared a 
classified catalogue of all the Australian species in the Herbarium, with their ranges in longitude, 
1 latitude, and elevation, as far as I could ascertain them, and added what further information I 
could obtain from books. At the same time I made a careful study of the affinities and distri- 
bution of all the Tasmanian species, and of all those Australian ones which I believed to be found 
in other countries. I also determined as accurately as I could the genera of the remainder, and 
especially of those belonging to genera which are found in other countries, and I distinguished 
the species from one another in those genera which had not been previously arranged. In this 
manner I have brought together evidence of nearly 8000 flowering plants having been collected 
or observed in Australia, of which I have seen and catalogued upwards of 7000. About two- 
thirds of these are ascertained specifically with tolerable accuracy, and the remainder are distin- 
guished from one another, and referred to genera with less certainty, being either undescribed, 
or described under several names, whilst some are members of such variable groups that I was 
left in doubt how to dispose of them. 
To many who occupy themselves with smaller and better worked botanical districts, such results 
as may be deduced from the skeleton Flora I have compiled for Australia may seem too crude and 
imperfect to form data from which to determine its relations. But it is not from a consideration 
of specific details that such problems as those of the relations of Floras and the origin and distribu- 
tion of organic forms will ever be solved, though we must eventually look to these details for proofs 
of the solutions we propose. The limits of the majority of species are so undefinablc that few natu- 
ralists are agreed upon them;* to a great extent they are matters of opinion, even amongst those per- 
sons who believe that species are original and immutable creations ; and as our knowledge of the 
forms and allies of each increases, bo do these differences of opinion j the progress of systematic science 
being, in short, obviously unfavourable to the view that most species are limitable by descriptions or 
characters, unless large allowances are made for variation. On the other hand, when dealing with 
genera, or other combinations of species, all that is required is that these be classified in natural 
groups; and that such groups are true exponents of affinities settled by Nature is abundantly capable 
of demonstration. It is to an investigation of the extent, relations, and proportions of these natural 
combinations of species, then, that we must look for the means of obtaining and expressing the 
features of a Flora; and if in this instance the exotic species are well ascertained, it matters little 
whether or not the endemic are in all cases accurately distinguished from one another. Further, in 
a Flora so large as that of Australia, if the species are limited and estimated by one mind and eye, 
the errors made under each genus will so far counteract one another, that the mean results for the 
genera and orders will scarcely be affected. As it is, the method adopted has absorbed many weeks 
of labour during the last five years, and a much greater degree of accuracy could only have been ob- 
tained by a disproportionately greater outlay of time, whilst it would not have materially affected the 
general results. 
With regard to my own views on the subjects of the variability of existing species and the 
fallacy of supposing we can ascertain anything through these alone of their ancestry or of originally 
created types, they are, in so far as they are liable to influence my estimate of the value of the facts 
collected for the analysis of the Australian Flora, unaltered from those which I maintained in the 
* The most conspicuous evidence of this lies in the fact, that the number of known species of flowering plants 
is by some assumed to be under 80,000, and by others over 150,000. 
b2 
