ARID PORTIONS OF SOUTH AUSTRALIA. Ill 



At various places on the Murray Flats west of Blanchtown, farming 

 operations have been carried on for several years. It is not uncommon 

 to see the farm fences composed of the "roots" or "stumps" of the 

 mallees. These are piled loosely into long and low walls. I was in- 

 terested to note that there were no especially large roots in the fences. 

 This agreed with what I had seen in excavations by the roadside in 

 which mallee roots had been in part exposed. From other observa- 

 tions also it appeared that the stem bases of the mallees of the region 

 were usually not large. So far as the roots of the mallee of the region 

 are concerned, it seems probable that they are largely, but not exclu- 

 sively, superficially placed. They are not infrequently exposed in 

 part by the removal of the soil by erosion, and under such circumstances 

 the stem base appears as a flattened crown lying close to the level of 

 the ground, from which the superficial absorbing roots radiate like 

 spokes in a wheel. 



MORPHOLOGICAL ASPECTS OF THE XEROPHYTIC FLORA 

 OF SOUTH AUSTRALIA. 



LEAF-SIZE AND LEAF-FORM. 



One of the striking features of the vegetation of South Australia 

 is the xerophytic stamp that characterizes every shrub and tree. 

 This impression is given on every side — on the plains about Adelaide, 

 in the Mount Lofty Ranges, on the Murray River fiats, on the rolling 

 Central Highlands, about Quorn and Mount Remarkable, as well as 

 in the far north and in the southwestern districts. Very naturally 

 the xerophytic characters increase with an increase in the dryness of 

 the habitat. Where the rainfall is most favorable the plants on the 

 whole are relatively large as well as abundant and the leaves they bear 

 are not only numerous but relatively large. Thus the differences 

 noted are those of degree and not of quality. 



The range in the modifications, however, may be extreme, amounting, 

 in effect, upon the contrast of the extremes, to qualitative differences. 

 Thus aphylly is occasionally met with in genera with leaf-bearing or 

 phyllodia-bearing species. A condition of aphylly connotes the ab- 

 sence of leaves at all times and at all stages of development, save 

 possibly in seedlings. There are apparently no perennials with de- 

 ciduous habit through which the condition of aphylly becomes a re- 

 curring one. On the contrary, the foliar organs, of whatever nature, 

 can be said to be constant, used in a restricted sense, and thus 

 are exposed fully to the greatest range of intensity of the environmental 

 conditions where the species occurs. The adjustments to the environ- 

 ment take place along different fines and naturally affect the shoots 



