549 



edaphic conditions within a short distance of each other, 

 because the climatic factor of rainfall has varied as a result 

 of some fortuitous circumstances, e.g., a local thunderstorm. 

 A further factor affecting this variability is interference by 

 man, which has been not inconsiderable in some places. This 

 interference is partly caused by the aborigines, who cut down 

 and uproot trees and shrubs around their camps in an aston- 

 ishingly reckless manner, and partly to the demand for wood 

 during the eonstruction of the railway line. 



The sand ridges have a rather varied flora, among- the 

 most prominent and generally distributed plants on the ridges 

 are Acacia linophyllfi , known as the "sandhill mulga" ; A. ligii- 

 lata, Dodonaea attenuata, and, rather less generally distri- 

 buted, Leptosiiermum laevigatum, var. minus. These, with 

 locally some quantity of Hakea leucoptera, Grevillea steno- 

 hotrya, Grevillea juncifolia, and Bossiaea JValkeri, mark the 

 earlier stages in the stabilization of the sand. Frequently 

 communities of these plants occupy the crest of the ridge while 

 the sides of it have others which represent the result of a 

 more stable condition. The most prominent of these are 

 mallee forms of Eucalyptus. The most common are E. oleosa, 

 E. leptophylla, and E. sp. ajfin. oleosa, while E. transconti- 

 neiitalis is rather more local. Other plants here are Acacia 

 Randelliana, A. Oswaldii, A. aneura, Eremophila alterni- 

 folia, and Cassia eremophila. In some parts Callitris verru- 

 cosa, Grevillea netatophylla, and Hakea midtilineata occur in 

 this situation. These last three species were all seen at 

 Immama, 20 miles east of Ooldea, but not in the immediate 

 vicinity. 



On some of the sand ridges near the margin of the plain 

 Casuarina lepidophloia occurred both on the sides and even 

 extending on to the crests of the ridge, but this was not 

 general. When the sandhills had become more stabilized the 

 mallee and its associated plants extended over almost the 

 whole, occupying both sides and crests. Indeed, the notable 

 Eucalyptus pyriformis seemed only on crests of ridges. 

 Whether the covering consists of Acacias and Leptosperm,um> 

 or mallees the canopy is not continuous, considerable spaces 

 being left between most of the plants. A marked feature, 

 and one most obvious with the plants on the crests, is the 

 presence of large quantities of dead branches and wood. 



Beneath the trees and bushes a moderate amount of 

 undergrowth occurred in some places, though in parts the 

 sand was practically bare. Of perennials, on the crests there 

 occurred Fiinelea microcephala , Rhagodia PreissH, while on 

 the slopes the ''porcupine grass" Triodia irritans was locally 

 very abundant, forming what appeared at a distance to be a 

 continuous cover; associated with it was Bassia echinopsila. 



