ARID PORTIONS OF SOUTH AUSTRALIA. 89 



TRANSITION FROM THE SANDHILLS TO THE NULLARBOR PLAIN. 



Along the eastern edge of the great plain there is at Ooldea a scat- 

 tered vegetation in which elements from the two physiographic areas 

 mingle to a certain extent. The soil conditions appear to differ from 

 those of the plain in the greater depth of soil brought about probably 

 by drifting of the sand from the adjacent sandhills. Because of this 

 condition the water relations of the transition are somewhat better 

 than they are for the plain as a whole. Here occur, among other 

 species, Kochia sedifolia, which possibly is most numerous ; Eremophila 

 alternifolia and possibly other species of Eremophila, Acacia kempeana, 

 A . aneura, and A . tetragonophylla. A few specimens of Casuarina lepido- 

 phloia were seen along the road to Fowler's Bay and Cassia sp. in 

 fairly large numbers. In places rather large areas were covered with 

 dead shrubs which had not been able to withstand the drought of some 

 preceding year; these appeared to be cassias. Finally, there were 

 remains of grasses, species not determined, and among other herba- 

 ceous forms, here and there appeared the cheerful flowers of Calan- 

 drinia balonensis with its odd fleshy and bright-green leaves. 



LEAF-FORM AND LEAF-SIZE. 



All of the perennials of the Ooldea region have pronounced xerophy- 

 tic characters, as would be expected from the nature of the environ- 

 ment to which the vegetation is exposed. Without taking up this 

 feature further at this time, attention may be called to the relatively 

 narrow leaves, or phyllodia, of the species. Indeed, it may be said 

 that all species which are not aphyllous bear leaves of this character. 

 The length of the leaves, or phyllodia, averages approximately 20 

 times the width. 



VEGETATION AND ENVIRONMENT AT TARCOOLA. 



PHYSIOGRAPHY. 



Tarcoola is the center of a gold-field of secondary importance and 

 is connected with Wilgena Run, a "station" of about 3,000 square 

 miles, formerly owned by A. J. Cocks esq., of Adelaide, whose knowl- 

 edge of the region has been generously placed at my disposal and who 

 in various ways very kindly forwarded my studies of the region im- 

 mediately around the village. 



Tarcoola is 257 miles west of Port Augusta and lies 392 feet above 

 the sea. Like Ooldea, it lies on the south edge of the western plateau. 

 The village is about 100 miles, as the crow flies, from the Bight. 

 Between it and Ooldea the country is undulating and about Tarcoola 

 it is hilly. To the east the general level sinks and the flat salt-lakes 

 region begins. At Tarcoola itself the plains between the hills con- 

 stitute the largest percentage of the surface. The Tarcoola hills, in 

 part at least, are granitic, of pre-Cambrian age, related to the out- 



