22 R. H. CAMBAGE. 



proportion in the more basic rocks, nor that it prefers 

 something which is only formed in the highly siliceous, but 

 rather that the porous state of the soil allows the moisture 

 to reach the plant, and so enables it to avail itself of the 

 particular food it requires. 1 



It is unquestionable that primarily the soil of any par- 

 ticular area is largely the product of the decomposing 

 geological formation in the locality, and the constituents 

 of the rock may be ascertained by analysis of sound freshly 

 fractured portions of it. By constantly observing the class 

 of rock selected by certain species, some of which show 

 very distinct preferences, information may be obtained 

 which would be of the greatest value in the selection of 

 sites for fresh plantations, and species which favour either 

 basic or siliceous rock-types could be planted in the form- 

 ations which during the test of ages in Nature's laboratory 

 they have found to be congenial. 



The soils produced from similar geological formations in 

 separate localities have not always the same effect upon 

 the local flora, the diversity being caused by the differences 

 in climate, rainfall, and aspect; but in areas where these 

 conditions remain the same, certain Eucalypts are typical 

 of particular geological formations. Examples in the 

 Sydney district may be seen in the distinct preference 

 shown for the siliceous Hawkesbury Sandstone formation 

 by Eucalyptus corymbosa, hcemastoma, capitellata, 

 Sieberiana, piperita, etc., and in E. hemiphloia and 

 tereticornis for the Wianamatta Shale, which contains 

 a much lower percentage of free silica. In the mountain 

 areas the same discrimination is exercised by various 

 Eucalypts in the selection of formations. The presence of 

 E. Andrewsi and Bancrofti may be taken as evidence 



1 See " (Ecology of Plants/' by Eug. Warming, ph.d., p. 70 (English 

 Edition) 1909, 



