HORN EXPF.DITION^NARRATIVE. 13 



Cretaceous rocks were not ca2:)ped with the hard clialcedonized Desert Sandstone, 

 and where, therefore, no gibbers have been formed. 



Sliortly after leaving Oodnadatta the track passes away from the telegraph 

 line, leaving the latter some miles to the west. We crossed two or three smaller 

 creeks, such as the Opossum and Storm Creek along which a few water-holes still 

 remained, and after three or four days came into the broad valley of the Macuml)a, 

 which during the winter montiis simply forms a succession of diy sandy beds 

 running parallel to one another with muddy water-holes here and there, which 

 after a few months of drought dry up completely. The approach to a water-hole can 

 always be told, not only by the greener patches of scrub and trees immediately 

 surrounding the water, Ijut by the twittering of innumeral)lf^ chestnut-e.-ii'ed 

 finches ( Tccniitpyiiia castaiwtis). The twittering of these pretty little birds may 

 always be taken as an indication that water is not far away : from the side of a 

 water-hole flocks rise as you approach, and their little grass nests are vei'y connnon, 

 as many as nine being seen on one occasion on one small shrub. They fall an easy 

 prey to such birds as the falcons, which will swoop down upon a flock and usually 

 carry oflf a little finch each time. Judging by their' numbers they must be prolific 

 breeders. 



There is not, however, much life as a general rule about these water-holes, ;i,nd 

 a yard away from them everything is as dry and parched as possible. In the dry 

 season the only moist place in Central Australia is actually in a water-hole. 



The lines of the water-courses are marked by belts of gum trees and acacias 

 — Eucalyptus ?-osfrafa, the river gum ; Eucalyptus niicrothcca, the swamp gum ; 

 Acacia ancura, the mulga ; Acacia cypcfop/iyi/a, the red mulga, a very local tree 

 extending across a narrow belt of country from east to west, a little w.ay to the 

 north of the old Macumba Station, and the stinking acacia, A. honialopliylla. On 

 the loamy flats, and even gibber plains, the most noticeable plant is Salsola kali, 

 ))opularly known as the Rolly-polly. It is, wlicn mature, one of the characteristic 

 prickly plants of the Lower Steppes, and forms great spherical masses perhaps a 

 yard or more in diameter. It is a constant feature of the Cretaceous nrea, and 

 gradually disappeared as we passed northwards into the Silurian district. 



The thin, poor scrub is made up largely of Cassias, Eremoplulas, Ilakeas, 

 and Crevilleas, all thinly scattered about, and with haid, spiny or coriaceous 

 leaves. Now and again, especially on the upland stony plains, were patches of 

 salt-bush {Atrip/ex rha_Q;odioidcs), the foliage of which has the characteristic and 

 well-known blue-grey tint, caused by the presence of a "mealy " secretion on the 



