ARID PORTIONS OF SOUTH AUSTRALIA. 105 



the Loranthaceae are not nearly so conmion here or elsewhere about 

 Quom as at Copley. 



Near the Port Augusta road and about 2 miles west of Quom are 

 other mallee scrubs in which there appear to be fewer species than in 

 the scrub just described. Low ridges, extending from the higher hills 

 and mountains to the Willochra Plain (plate 28a), are covered with 

 Evxidlyptvs oleosa and E. odorata as the dominant species. Here were 

 also found Dodonoea bursarifoUa and Pholidia santalina (syn. Ere- 

 mophild) (plate 23a). 



Where the valley ascends to Pichi Richi Pass, on either side of the 

 road are hills a portion of which, as just described, bear mallee scrub; 

 but some of the hills bear scattered low shrubs and are heavily covered 

 with grass. Of the shrubs. Acacia continua (plate 23c) is possibly the 

 most common, although it occurs but sparingly. Widely scattered 

 specimens of Casuarina sp. also occur, but the grasses Triodia irritans, 

 the porcupine grass or Spinifex, and Trichinium spathulatum are the 

 dominant species. 



Somewhat higher ia the valley the mallee and other species of Etica- 

 lyptus come to the valley floor and here the grass is absent. It seems 

 possible, although this will require verification, that the mallee-covered 

 ridges above referred to are shale, while the grassy hills are quartzite. 

 In the vicinity of Quom, so far as my observation went, it appeared 

 that bunch-grass and Casuarina were both found where there was an 

 outcropping of the latter. As an example of this, the vegetation of 

 the quartzite ridge east of the Mount Arden road dnd about 3 miles 

 north of Quom may be given. 



Vegetation of Low Hills. 



Mention has already been made that the low ridges which extend 

 in a generally easterly direction to the Willochra Plain from the higher 

 hills and mountains are in part at least covered with mallee and that 

 certain of the hills near the Pichi Richi Pass, on the Port Augusta 

 road, are grass hills on which there are scattering woody perennials. 

 The vegetation of three other hills or ridges should be mentioned. 

 Of these, the ridge last referred to as being along the eastem side of 

 Mount Arden road has vegetational features of interest. On the 

 western slope is a heavy covering of bunch-grass growing very thickly, 

 Triodia irritans and Trichinium spathulatum, with a few and scattering 

 specimens of "mallee" and Xanthorrhaea semiplana (plate 28c). Near 

 the summit of the ridge the grass becomes more scattering and Xanthor- 

 rhoea semiplana occurs in considerable numbers. On the top, mallee 

 dominates the woody perennials, although Callistemon teretifolius also 

 occurs (plate 23b). Somewhat lower on the ridge and on the southern 

 slope mallee ceases and Casuarina stricta is met. Whether, as may be 

 possible, the distribution of the mallee is coincident with the change 

 from quartzite to shale was not determined. 



