VI. 
Charles Austin Gardner. 
it extends almost uninterruptedly through and around the Hamersley Range 
and dominates the northern part of the Eremean Province between the Mulga 
Bush formation and the savannah formations of the north. In some places 
it intrudes into the Mulga Bush country w'here the red sand provides the 
necessar^^ environment, but here it loses much of its character by reason of 
the presence of the mulga trees and other shrubs. In its typical form, the 
Triodia Steppe is either entirely devoid of trees and shrubs, or there may be 
a fe-w isolated trees, such as Acacia pryifolia near the north-west coast, or 
scattered Eucalyptus trees in the interior, or some admixture of Eremophila 
and Cassia. There are large areas to the north-east of Wiluna, and east of 
the Carnarvon Range, where, as far as the eye can see there is nothing but 
Triodia^ unrelieved by any shrub or tree. It is only under the more favourable 
conditions of higher rainfall towards the Northern Province, that trees become 
relatively important, and the steppe formation merges into the savannah, and 
other grasses compete with Triodia, e.g., Eulalia, Chrysopogon, and Eriachne. 
Before reaching the Fitzroy River it merges into the Pindan country, in whicli 
Acacia becomes predominant. 
Just as to the north it takes on something of the characteristics of the 
savannah and the Pindan, so to the south, in the Mulga formation, the in- 
fluence of the winter rainfall causes some local alteration to the physiognomy 
of the steppe by the addition of shrubs and trees, and the formation receives 
to some degree the addition of the ephemeral winter flora wJiich characterises 
the Mulga country. The steppe formation remains, however, a formation 
restricted to the Nullagine rocks and the red sand, and nowliere is it found 
away from this soil type, neither does it flourish in the absence of summer, 
precipitations. Tlie drier the conditions, so much more does Triodia become 
dominant, until it enters into the true desert. 
(f) THE DESERT. 
While, as its name would imply, the whole of the Eremea conforms with 
the broader deflnition of what ecologists term desert, there is an area close 
to the centre of Australia which complies with desert in its more limited 
sense. The extreme aridity of the country, the absence of any permanent 
surface water, the high annual mean temperature, and the extreme diurnal 
range, as well as the paucity of the vegetation, are all conditions characteristic 
of deserts in other parts of the wmrld. This tract, in Western Australia, lies 
betv-een the latitudes of 20° and 25°, and extends eastwards of longitude 122^^ 
as far as longitude 132°. 
For our accounts of this country we have to rely largely on the published 
descriptions of the few intrepid explorers who have penetrated the region. 
These accounts differ to some extent ; some state that there is no desert in 
Australia, meaning that there are no large areas of bare sand ; others speak 
of it in unmistakable terms. The fact that no botanical investigations ha^’e 
been made, renders a true conception somewhat difficult. 
In general, the region consists of large areas of sand ; sandstone cliffs 
mark the escarpments of plateaux which are either sand or gibber-plains, 
while there are depressions of sandy loamy soil. But it is the red sand that 
prevails, either in the form of undulating country, or heaped into long ridges 
or dunes which have in general a meridional trend, or bear in a N.N.M .-b.S.E. 
direction. These dunes or ridges are either quite devoid of vegetation, or are 
populated by sj arse Triodia and a few harsh xerophytic shrubs, while in the 
trough-like depressions between tlie ridges there are sparse dwarfed trees and 
shrubs ; on the other liand there are extensive undulating areas of bare wind- 
