Apr., 1923] 
CAMPBELL-AUSTRALASIAN BOTANICAL NOTES 
185 
A very large majority of the 4,000 species of West Australia are confined 
to that state, and there are many endemic genera as well as species. A 
notable feature of the flora is the remarkable number of species within a 
genus. 3 Drosera has 45 species, Candollea 84, Boronia 44, Goodenia 48, 
Grevillea 70. 
Wallace (Island Life, 2d edition, p. 494) believes that Southwest Aus¬ 
tralia represents the remnant of an ancient, more extensive, isolated land 
area within which were developed the ancestors of the present autochtho¬ 
nous Australian flora, and this view seems to have much probability. There 
is strong evidence, as has already been stated, that in Cretaceous times 
Western Australia was completely separated from the eastern part of the 
continent, the western portion of which was probably united with New 
Guinea. The flora of North Queensland and coastal New South Wales 
still retains a large Malayan element, the “scrubs” of Queensland being 
predominantly Malayan in their flora. 
It is highly probable that in early Tertiary times, before the Union of 
East and West Australia, the former region was occupied by a flora of ex¬ 
clusively Malayan character, while in the western continent the ancestors 
of the modern Myrtiaceae, Proteaceae, and other characteristic Australian 
types were completely segregated. 
It is not unlikely that this western continent, owing to the intrusion of 
the sea in Cretaceous times, had a more uniform and less arid climate than 
now prevails in most of West Australia. It may have been like that now 
found in the extreme southwest, where a great majority of the existing 
species occur. 
With the establishment of the connection between east and west, the 
existing climatic conditions were developed within the great arid central 
regions which occupy so much of the present continent. 
With the increasing aridity in Western Australia is to be associated 
the evolution of the predominant xerophytic habit found in most of the typ¬ 
ical Australian plants. These xerophytic forms apparently migrated east 
and north and took possession of most of the eastern territory. At the 
present time, all that is left of the ancient flora of northeastern Australia 
is probably the “scrub,” confined to the narrow coastal belt of Queensland 
and New South Wales. This scrub is not continuous, but is surrounded by 
much larger areas of xerophytic Eucalyptus forest. 
A few species of Eucalyptus and the allied genera, Tristania and Ango- 
phora, grow in some of the rain forests, and it may be that the few Proteaceae 
which occur in the rain forests, like Grevillea robusta , Macadamia, and Sten- 
ocarpus, are descendants of Western immigrants which have become 
adapted to the changed environment. 
If the assumption is correct that the autochthonous Australian vegeta¬ 
tion originated in Western Australia, the question then arises as to the origin 
of the ancestral forms from which this flora descended. 
s Maiden, loc. cit., pp. 183-199. 
