60 PLANT HABITS AND HABITATS IN THE 



south base of O'Halloran's Mount may be found E. negleda (plate 5b). 

 In the same situation a few examples of an undetermined half-shrub and 

 several annuals, also undetermined, were seen. 



Although the species mentioned in the preceding paragraph are 

 to be found very sparingly on both the upper and the lower plains, 

 the former was especially in mind when writing the description; 

 and, so far as one can judge, the vegetation of this plain, at least in the 

 vicinity of Oodnadatta, has been Uttle affected by the presence of man. 

 No trees occur on it and the shrubs of the plain are apparently not 

 found useful either by man or beast. On the lower plain, however, 

 there are indications that formerly the number of individuals may 

 have been greater than now. Dried remains of salt bushes are to be 

 found here and there, and persons familiar with the region say that 

 such forms were formerly fairly abundant on this plain. It seems prob- 

 able, also, that after heavy rains, which occur at widely separated 

 intervals, the face of the lower plain may be clothed with annuals, 

 including grasses, and that they may be of such size and abundance 

 as to completely hide the surface of the ground; and, although there 

 are no trees on this plain, they may be found along water-courses con- 

 necting it with the upper plain — ^for example, Acacia cambadgei occurs 

 sparingly in such a drainage channel leading from the upper to the 

 lower plain at a place about 4 miles to the west of Oodnadatta (plate 3a) . 

 Eremophila neglecta and E. latrobei also occur in such situations. 



VEGETATION OF AND ABOUT THE SANDHILLS. 



Across the lower plain and about 3 miles to the east or southeast of 

 Oodnadatta is an area where sandhills and clay-pans are the most 

 characteristic features of the physiography. On the way to the hUls 

 the plain is found to sustain a sparse population of saltbushes of various 

 kinds which were not studied particularly, and viewed from the plain 

 the distant sand ridges appear to be fairly well covered with vegetation. 

 Upon drawing near the hills a comparatively large number of small 

 trees and shrubs are also to be seen. But the near view of the sandhills 

 reveals the fact that the vegetation is very diffuse and composed 

 almost exclusively of a single form. The clay-pans which lie between 

 or by the sandhills were found to be devoid of vegetation, although 

 when flooded such a form as the "nardoos," Marsilia spp., may be found. 

 On the rims of the clay-pans saltbushes occur, but not in abundance. 



The characteristic species of the sandhills is the sandhill mulga. 

 Acacia linophylla. On the dunes the species has the habit of a large 

 shrub, but occasionally a central stem is formed. It is about 5 meters 

 in height. The habit of the species is shown in plate 4b. The leaves, 

 or rather phyllodia, are relatively few in number (plate 5a), about 

 15 cm. in length and about 2 mm. wide. They are fairly rigid and 

 have an attenuated but not a spiny tip. At the time of my visit, 



