ofS.E. $ 8.W. Australia.'] 



INTRODUCTORY ESSAY. 



liii 









Speciea. 



Sp. found in S.E. 



*Adenanthoa .... 15 







*Beaufortia 







14 







*Agonia . . 







14 







Phebalium . . 







13 



1 



*Hypocalymna 







13 







Tracbymene 







13 







Podolepis . . 







13 



1 



*Anarthria . . 







13 







Opercularia 







12 







Myoporuin . . 







12 







Atriplex . . 







12 



3 



Cassytha . . 







12 



1 



Tbelyraitra 







12 



5 





Species. 



Sp. found 



*Sphaerolobium 



11 







*Eutaxia . . . 



11 







Haloragis . . . 



11 



2 



*Astartea . . . 



11 







Xanthosia . . . 



11 







Helichrysum . . 



11 



3 



*Halgania . . . 



11 







*Microcorys . . 



11 







Ebagodia . . . 



11 



2 



*Synapliea . . . 



11 







Casuarina . . . 



11 



1 



*Virninaria . . . 



11 







This instructive table puts the most important differential features of south-eastern and south- 

 western Australia prominently before the eye, and I would point out : — 1. How greatly larger the 

 genera of the south-western Flora are, there being 80 genera with upwards of 10 species in its 

 column, and only 55 in the south-eastern. 2. That the 55 genera of the south-eastern Flora contain 

 about 1,260 species, and the 55 highest of the south-western 1,727 species. 3. That of these 55 south- 

 western genera 36 do not appear at all in the south-eastern list, and 17 (marked with a*) are 

 absolutely confined to the south-west, or almost so. 



Altogether, I find the proportion of genera to species in the south-western Flora to be 1 : 6, and 

 in the south-eastern 1 : 4. This increased number of genera in south-eastern Australia over the 

 south-western is mainly due to the presence of more Antarctic, European, New Zealand, and Poly- 

 nesian genera in the south-east, to which I shall hereafter allude. 



The proportion of species belonging to peculiar or endemic genera in the south-west is about 

 one- third of the whole, and in the south-east one- sixth. 



The proportion of species common to other countries in the south-west is about one-tenth 

 of the Flora, and in the south-east one-sixth. 



There are about 180 genera, out of about 600, in south-western Australia that are either not 

 found at all in south-eastern, or that are represented there by a very few species only, and these 180 

 genera include nearly 1,100 species. 



Of generally diffused Australian genera that are absent in the south-west, I find Viola, Pohjgala, 

 Epacris, Lycopus, Ajuga, Smilax, and EriocauJon ; and of European genera which occur in that 

 quarter, but which I have not seen from elsewhere in Australia, are Echinospermiim, Eritrichium. 

 Orobanche, Althenia, and Lepturus, several of which I suppose to be introduced, and, if so, will 

 soon be found in other colonies. 



This curious case of great differences in the genera and species of the two quarters of a small 

 continent, accompanied by an increased number of species in the smaller and more isolated quarter 

 of the continent, which is, further, by far the most uniform in physical conditions, will no doubt 

 eventually be found to offer the best means of testing whatever theory of creation and distribution 

 may be established. In the meantime, the theories which I have sketched in the early pages of this 

 Essay cannot, in the present state of our geological knowledge of Australia, be brought to bear 

 fully upon it. That no Natural Order, but that many genera, and a whole Flora of species, should 



