liv. 
Charles Austin Gardner. 
and tlie violet and white of Calotis, Brachycome, and Erodiophyllum, while 
the masses of the vetch-like Swainsonas intermingled with the whole provide 
a herbaceous floral wealth unexcelled in any other formation. This brief 
pageantry continues only for a few weeks ; two months later there remain only 
the withered remains of stalks as evidence of this. 
On the other hand, the summer rains call into being an almost equal rich- 
ness of grasses and Trichinium, the former consisting mainly of short-lived 
annuals such as Aristida and Chloris, Brachiaria, Setaria and a few others, 
at the same time reviving the dormant stocks of the perennial species such as 
Eragrostis, Neurachne, Triodia, Plectrachne, and Eriachne. Stipa, the prin- 
cipal representative of the sclerophyllous woodland, is entirely absent, and 
Amphipogon does not extend far into the formation from the south. The 
mulga-bush formation exhibits this biannual succession to a degree not ob- 
served in any other formation in Western Australia. In both cases it is 
short-lived, without a sufficient rainfall it does not occur, and for years no 
annual species may appear. 
The true mulga (Acacia aneura) is the most common species in the mulga 
bush, and its range extends throughout the formation,, or practically so. 
It is most typically developed in those soils with a hard subsoil close to the 
surface ; in the lighter deeper soils it becomes scarce or entirely disappears, 
and its place is taken by Acacia linophylla in the area between the Minilya 
and Murchison districts near the coast, while farther north, between the 
Minilya and Fortescue Rivers, Acacia xiphophylla assumes a dominant role, 
but even here, in the hard-pan soils, or in clay depressions, Acacia aneura 
reappears, and once more becomes dominant to the east of Mount Bruce 
in the upper Fortescue watershed. 
Over very large areas of fiat or undulating country the Acacia species which 
dominate the formation provide a uniformity of contour and physiognomy 
to which the formation owes its name. The various species so closely resemble 
each other even when in flower, that it is often impossible to determine ac- 
curately the component species, unless pods and seeds are available. The 
species are so plastic, that it is probable that ultimate research will disclose 
fewer species than those already described, since the so-called species appear 
to merge into each other. The landscape resembles a flat or rolling sea of a 
dull grey-green, relieved only by the rocky eminences, and the scattered 
salt-lakes which glisten in the sun. 
The stony hills and ‘ ‘ breaka-ways ’ ’ provide some relief from this monotony, 
for here we find a more varied flora. Here we find the bright green masses of 
Dodonaea filifolia covered with crimson hop-like fruits, the green-leaved Plec- 
tronia, Santalu7ni Hibiscus, Eriostemon^ Grevillea extorris, an occasional Melaleuca 
or Tliryptomene, and the green-leaved Acacia quadrimarginea, mixed up with 
brilliant masses of Eremophila, and the large-spiked Trichinimn rotundifolium, 
•with several herbaceous species of the same genus, together with the dense 
Cupressus-like masses of dull green Callitris glauca. The white corky barked 
Trihulus platypterus, with its pale pinnate leaves and yellow star-like flowers 
adds a bizarre note to this strange assembly in an environment so poor in forms. 
(d) THE HALOPHYTIC FORMATIONS. 
Throughout the Eremea, salt-pans, clay-pans, and the remains of former 
ancient river systems are scattered. They form perhaps the most striking 
physiographic feature of the landscape, appearing i ntensely bright because of 
the reflected light of the salt crystals of their dry surfaces, because of the 
remarkable mirage, and lastly because of the distinctive grey vegetation which 
