Tut’, Vkgetation op Western* Austijalia. 
XXVll. 
These eastern species and groups bear the same relationship to tliose 
of South-Western Australia that the groups in South Africa and SoutJi America 
bear to the Australian ingredients of the Antarctic Klement. 
Whether South-Western Australia w'as the cradle of the Australian Ele- 
ment, or whether it is here alone that it has maintained its floristic stability, 
is a ({uestion which has not yet been decided. Wlien we consider tlie liigh de- 
gree of endemism within the area, and its ec^ological stability, one is inclined 
to the foi-mer view, but, as Diels has pointed out, the occurrence of the \-ast 
epicontinental sea of Cretaceous times must hav(‘ caus('d a division of what may 
originally have been an ancient pan-Australian flora, and the present distri- 
bution of such genera as Borya, Petrophila , Jsopogon, Grevillea, and Banksia, 
to enumerate a few only, lends a.dehnite support for tlie tlumy of the previous 
existence of a pan-Australian Element. ]n any cas(‘, it is in South-Western 
Australia alone that the true Australian flora is today most richly developed 
within a climatic and geologically distinct entity, in an almost perfect state 
of efjuilibrium which is disturbed only by tlu' gradual process of climatic 
desiccation in operation everywhere. It is true that a disturbing influence 
has to some extent been at work since the ach-ent of settlement : agriculture, 
with grazing, fire, and the plough, has done much to bring about important 
local changes in the country’s physiognomy, but tlu* work of man, and the plants 
which he has brought wdth him, including those aliens which we regard as weeds, 
although of great importance in man’s particular economy have, in the main, 
proved quite ineffective as a permanent invading force when subjected to 
competition under natural conditions with the indigenous vegetation. 
III.—PHYSIOGRAPHY. 
Western Australia consists almost entirely of a low" plateau with an 
average elevation of between 1,000 and 1,500 feet. Between Point Culver 
and Eyre on the south coast, between the King Leopold Range and Van- 
sittart Bay in the Kimberley district, and in a few" other places, this plateau 
extends to the coast. In other places, e.cj., between Eyre and Eucia, and 
along the western coast betw'een the Moore and Vasse rivers, the plateau 
descends rather abruptly to a narrow littoral plain. In the north-west, be- 
tween the Murchison River and Broome, the plateau descends gradually to 
the coast, or the escarpment is far inland, exc^ept in the Pilbarra district, 
where the Hamersley massif extends almost to the coast at Vlaming Head, 
and again in the vicinity of Roebourne. While little is knowm of the contours 
in the vicinity of the Eighty-mile Beach, the Gascoyne, Ashburton, and Eortes- 
cue rivers in their lower courses flow* over broad alluvial flood-plains. 
The surface of the plateau is mostly flat or gently undulating. According 
to Jutson, the main plateau represents what is probably a vast uplifted pene- 
plain now in a state of arid erosion, bearing the residuals of a former higher 
plateau which has suffered very considerable erosion. There are no mountains 
in the sense of large folded and not much denuded systems, and the high 
points w"hich rise above the existing plateau are in the main either residuals 
of the former higher plateau erosion, or fault blocks. Tlie highest elevations 
are found in the Hamersley Range, w"hcre Mount Bruce attains 4,024 feet. 
In the Kimberley district, the King Leopold Range rises to nearly 2,000 feet. 
This range is the escarpment of the Hann ])lateau which extends almost everv- 
where to the coast to the north and west, and is boun{ted on the east by the 
Durack Range. It culmina,tes in Mount Hann (2,800 feet). In the south- 
west, the main physical features are tlie Stirling Range — a system of isolated 
peaks, of which Coyanarrup is the highest (3,(>40 feet) — while to the south 
is the Porongorup Range, and parallel with the soutli coast is a system of 
