ARID PORTIONS OF SOUTH AUSTRALIA. 93 



main been sufficiently characterized in different parts of this study. 

 It will be sufficient, therefore, to sketch briefly the habits of one not 

 hitherto met, namely, Cassia eremophila. This attractive shrub was 

 in flower at the time of my visit. An especially interesting feature 

 is the character of its leaves. It is one of the few species outside of 

 the acacias which has phyllodia. The leaf is compound, with leaflets 

 about 10 mm. in length. The leaf-stalk is broad, however, and upon 

 the falling of the leaflets it persists in carrying on the photosynthetic 

 function. This is exactly the occurrence in certain species of Acacia, 

 although in some the leaf-forming habit has been lost and phyllodia 

 only are organized. 



VEGETATION AND ENVIRONMENT AT PORT AUGUSTA. 



PHYSIOGRAPHY. 



Port Augusta is situated at the northern termination of Spencer's 

 Gulf. The topography of the region immediately about the place 

 is very diverse. Some of the most striking physiographical features 

 may be briefly described. The head of the gulf, here very narrow, 

 is surrounded by a belt of sandhills, usually of no great height. Back 

 of the dunes, more especially to the north, are depressions which do 

 not have adequate surface drainage, or none at all, and which carry 

 an excess of salts. These are the outlyers of the extensive "lake" 

 district, containing Lake Gairdner, Lake Torrens, and (among others) 

 Lake Lagoon, the latter extending about 200 miles north and west, 

 and somewhat less to the north. To the west and southwest and 

 beginning about 15 miles distant are flat-topped (pre-Cambrian) 

 "tent-hills," remnants of a formerly extensive higher land-level. 



The country immediately surrounding the table mountains is some- 

 what higher than the belt of dunes and salt spots nearer the gulf. 

 Turning to the east we find, beyond the lowlands, western members of 

 the Flinders Ranges extending in a generally north-south direction and 

 distant about 12 miles from the gulf. Between the foothills and the 

 dune-salt-spot region by the gulf are gently sloping plains or bajadas. 

 The mountains are sierras with sharply irregular sky-line, character- 

 istic of the mountains of arid regions. Of the highest peaks, the 

 most important are Mount Brown (altitude 3,500 feet) and Devil's 

 Peak, about as high. It will be seen, therefore, that the situation of 

 Port Augusta, in relation to the mountains and to the gulf, as well 

 as to the vast arid region to the north and west, is such as to give the 

 region climatic conditions, on the whole, unlike those of any of the 

 regions elsewhere met in the course of the present studies. There is 

 also not a little variation in plant conditions because of the differences 

 in altitude and those of aspect, soil, drainage, and moisture which 

 altitude differences entail. 



