492 



ISLAND LIFE 



PAET II 



The actual Australian flora consists of two great 

 divisions — a temperate and a tropical, the temperate being 

 again divisible into an eastern and a western portion. 

 All that is most characteristic of the Australian flora 

 belongs to the temperate division (though these often over- 

 spread the whole continent), in which are found almost all 

 the remarkable Australian types of vegetation and the 

 numerous genera peculiar to this part of the world. 

 Contrary to what occurs in most other countries, the 

 tropical appears to be less rich in species and genera than 

 the temperate region, and what is still more remarkable 

 it contains fewer peculiar species, and very few peculiar 

 genera. Although the area of tropical Australia is about 

 equal to that of the temperate portions, and it has now been 

 pretty well explored botanically, it has probably not more 

 than half as many species.^ Nearly 500 of its species are 



^ Sir Joseph Hooker informs me that the number of tropical Australian 

 plants discovered within the last twenty years is very great, and that the 

 statement as above made may have to be modified. Looking, however, at 

 the enormous disproportion of the figures give in the ' ' Introductory 

 Essay" in 1859 (2,200 tropical to 5,800 temperate species) it seems hardly 

 possible that a great difference should not still exist, at all events as 

 regards species. In Baron von Miieller's latest summary of the Australian 

 Flora {Second Systematic Census of Australian Plants, 1889), he gives the 

 total species at 8,839, of which 3,560 occur in West Australia, and 3,251 in 

 New South Wales. On counting the species common to these two colonies 

 in fifty pages of the Census taken at random, I find them to be about 

 one-tenth of the total species in both. This would give the number of 

 distinct species in these areas as about 6,130. Adding to these the species 

 peculiar to Victoria and South Australia, we shall have a flora of near 

 6,500 in the temperate parts of Australia. It is true that West Australia 

 extends far into the tropics, but an overwhelming majority of the species 

 have been discovered in the south-western portion of the colony, while the 

 species that may be exclusively tropical will be more than balanced by those 

 of temperate Queensland, which have not been taken account of, as that 

 colony is half temperate and half tropical. It thus appears probable that 

 full three fourths of the species of Australian plants occur in the temperate 

 regions, and are mainly characteristic of it. Sir Joseph Hooker also 

 doubts the generally greater richness of tropical over temperate floras which 

 I have taken as almost an axiom. He says: "Taking similar areas to 

 Australia in the Western World, e.g., tropical Africa north of 20° S. Lat. as 

 against temperate Africa and Europe up to 47° — I suspect that the latter 

 would present more genera and species than the former." This, however, 

 appears to me to be hardly a case in point, because Europe is a distinct con- 

 tinent from Africa and has had a very different past history, audit is not a 

 fair comparison to take the tropical area in one continent while the temperate 

 is made up of widely separated areas in two continents. A closer parallel 

 may perhaps be found in equal areas of Brazil and south temperate America, 

 or of Mexico and the Southern United States, in both of which cases I 



