852 



OCCURRENCE OF A LIMESTONE-FLORA. AT GROSE VALE, 



itself, in so far as it does not operate physically, cannot be the 

 cause of differences in the flora, for not only can calcicolous 

 plants be cultivated in soil that is poor in lime, but silicicolous 

 plants, and even bog mosses, which are regarded as pre-eminently 

 calciphobous, can grow vigorously in pure lime-water, if the 

 aqueous solution be otherwise poor in dissolved salts. It has 

 been overlooked that nearly all lime-soils are rich in soluble 

 mineral substances, and this wealth excludes plants belonging to 

 poorer soils; beyond this, the important physical characters of 

 calcareous soils come into play."|| 



As to where the plants forming this flora came from, it seems 

 sufficient to regard them, like the plants of the Blue Mountain 

 gullies, as remnants of the old tropical flora, which at one time 

 extended as far south as Victoria. Superior conditions in 

 circumscribed localities have enabled these remnants to persist, 

 while the rest of the country has become occupied by the present, 

 dominant, hardy flora which the drier conditions of to-day have 

 evolved. 



The rainfall is good, about 33 inches.U Kurrajong Heights, 

 three miles away, and 1,000 feet higher, averages 50 inches per 

 annum. The moisture-capacity of the soil is equal to that of the 

 shale, but its capillarity is much greater. The less of water by 

 evaporation must, however, have been largely checked, before 

 any clearing had been carried out, by the dense shading of the 

 soil. The area certainly gains moisture by soakage from the 

 steep slopes above. The road remains moist after rain, long 



II Warming, E., " Ecology of Plants." 1909, p.58. 

 H Of late years there has been a general diminution of rainfall in this 

 district (see Balletin No. 2, Commonwealth Bureau of Meteorology, 1908). 



For the following figures I am indebted to Mr. W. S. Arnold, who lives 

 not far from the limestone-outcrop. 



Compare 

 Richmond 



1903. 



42 -24 

 3.3-32 



1904. 



37-96 

 33-95 



1905. 



26-18 

 22-84 



1906. 



25-17 



17-17 



1907. 1908. 



21-35 

 17-77 



29-48 

 25-06 



1909. 



25-98 

 23-07 



Average, 29 

 years = 29 -90 



