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THE VARIABLE CHARACTER OF THE VEGETATION 

 ON BASALT SOILS. 



By H. I. Jensen, D.Sc. 



In my papers to the Society on the Glass House Mountains, 

 and the East Moreton District of Queensland, I emphasised the 

 point that, in these parts, the basalts were invariably covered 

 with dense scrubs, whereas the sandstones and trachytes sup- 

 ported only a forest-flora. In my paper on the Geology of Mt. 

 Flinders and the Fassifern District, I pointed out that, around 

 Engelsburg, the trachytes were covered with scrubs, whereas the 

 basalts in all the vicinity could boast only a sparing amount of 

 forest. 



Still more recently, Mr. R. H. Cambage, F.L.S., in the Proceed- 

 ings, has called attention to the want of forest-vegetation on the 

 basic rocks of the Monaro Plains, while the more acidic granites 

 and porphyries, in that same district, support a fair amount of 

 forest. 



An observer acquainted only with the barren basaltic outcrops 

 which occur isolated on the Western Plains, and in the Murrum- 

 bidgee basin, might well look upon basalt as a curse from an 

 agricultural point of view; while it is hard to dissuade the man 

 who has traversed the Darling Downs of Queensland from look- 

 ing upon basalt as the source of our richest agricultural lands. 



It is the object of the present note to explain why so many 

 types of vegetation occur on basalt in different parts. 



The character of the vegetation on any geological formation 

 depends essentially on three factors — (1) the mechanical and 

 chemical composition of the soil; (2) the character of the subsoil, 

 and (3) the climate and climatology. 

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