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formations, collating them is a matter requiring the attention of men of mature 
judgment, who alone can interpret the results or submit tentative interpretations of 
value. 
Mr. E. C. Andrews, 13.A., Geological Surveyor, Sydney, himself an earnest 
worker on the subject, has favoured me with the following observations:— 
In New South Wales, it would appear that climate is the chief controller of plant growths, and 
the climate in turn is mainly controlled by the topography. The wild and tumultuous profiles of the 
eastern aspects of the north and south ranges near the coastal area are composed of all types of siliceous 
and ferro-magnesian rocks ; nevertheless, in the gorges of this well-watered area, jungle growths may be 
found alike on granites, slates, and basalts. The dense sandstones, however, even in this tract appear to 
have their own distinct flora. 
In proportion as shelter and moisture decrease, so does the factor of soil composition come ever 
more prominently into play. 
One of the generalisations made in the study of the greater problems of Australian botany, is that 
of Mr. R. H. Cambage, namely, that in rocks and soils of great porosity the character of the vegetation is 
most marked. 
This great porosity is found in excessively sandy soils, such as those derived from the acid sand¬ 
stones, quartzites, and granites of various geological ages. 
It is not so much a question of excessive silica percentage in the soil—as may be proved by an 
examination of acid rhyolite soils—as it is a question of the presence of abundant fi’ee silica. The plant 
facies of a rock or soil possessing such an abundant free quartz content is so remarkably distinct as to 
come with the force of a revelation to workers accustomed only to clay soils. 
It is, of course, possible that sandy soils may contain potash as derived from granites, but this can 
scarcely obtain on our sandy coastal plains, where the potash would be leached out; nevertheless the plant 
facies is distinct and the vegetation rich in species. 
It is to Mr. Cambage again that we are indebted for our knowledge of the relative paucity of species 
on rich clay soils. This appears to be due in great measure to the lack of porosity in such soils, as 
capillary attraction is at a minimum in such rocks, but at a maximum in sandy soils. 
The great trees which grow on rich soils break up the clays themselves, and thus gain access to the 
rich stores of magnesia, iron, lime, potash, and soda foods therein, while the luxuriant grasses on such soils 
simply depend for nutriment on the surface food, and perish so soon as the precipitation ceases. Grasses 
for this reason thrive but poorly on porous sandy soils. But plants with long roots may grope easily 
through the porous soils, but these again are stunted because of the relative absence of rich plant-foods. 
Prostanthera Leichhardtii is a remarkable example of a plant which, in the writer’s experience, is 
absolutely confined to one type of dense pre-Silurian sandstone ridge. The spinifex and Acacia triplera, 
also of the Shuttleton-Mount Hope district, are strictly delimited by the sandy and sandstone wastes in 
that region. 
Following are some notes taken from a paper on the silvicultural conditions 
of New South Wales native trees, which was published by me in the Agricultural 
Gazette of New South Wales in January, 1906 :— 
The differentiation of the earth’s vegetation is controlled by three factors— 
(а) Heat (see an Isothermal map). 
(б) Atmospheric precipitation (including winds). (See the Observatory Rain Map.) 
(c) Soil (see the Geological Map of the Geological Survey, which is very suggestive in this 
connection). 
“ Heat determines the flora, climatic humidity the vegetation ; the soil as a rule merely picks out 
and blends the material supplied by these two climatic factors, and on its own account adds a few 
details.”—(Schimper.) 
We have various kinds of climate, which have considerable influence on the vegetation, c.g .— 
1. The salt-laden air of the coast, often accompanied by winds. 
2. The forcing steamy atmosphere of the “ brushes.” 
3. The cold, bracing atmosphere of the table-lands. 
4. The dry atmosphere of the western plains. 
99341—C 
