478 PROCEEDINGS OF SECTION D. 



interest to note that tlie turpentine is not typical of tlie pure Hawkes- 

 bury sandstone, but flourishes best where the sandstone is mixed with 

 the shale, or in the sindy gullies, and is probably affected by some 

 condition of drainage or moisture. 



A well known locality where the feature can be studied is at Spring- 

 wood, on the Western Railway line. This is a point on the margin of 

 the shales, which are shallow in consequence, but it would seem that 

 had their denudation been completed, this locality would be without 

 its turpentines, which at present contribute so much to the beauty of 

 the local landscape. 



Apart from geological considerations, Syncarpia laurifoUa seems to 

 be much restricted in its westerly course by climatic conditions, and in 

 no instance is it able to reach the vicinity of the great dividing range, 

 but, south of the Hunter, is usually confined to that part of the sheltered 

 coastal belt below an altitude of about 2,000ft. 



Eucalyptus hemipholia F. v. M., the common box of the Sydney 

 district, exhibits exactly opposite geological tastes to Si/ncarpia lauri- 

 foUa, for it is one of the commonest trees to be found growing on the 

 deep Wianamatta shale, and is practically absent from the Hawkesbury 

 sandstone. Some instances of its occurrence on this latter formation, 

 however, have been noticed on the Macdonald River, a tributary of the 

 Hawkesbury. In this locality the grouping of various species was 

 found to be most unusual and puzzling. One example was that Eu- 

 calyptus hemipholia was found growing beside Angophora lanceolata, 

 Cav., a so-called red gum of Port Jackson, on a formation which, from 

 its horizon, could only be Hawkesbury sandstone. Now, A. lanceolata 

 is never found on the deep shales, but in the Sydney district is restricted 

 to the sandstone, and is therefore rarely associated with the box, except 

 at the points of contact between the two formations. The occurrence 

 of the unusual associations in the locality named was found on further 

 examination to be due to the introduction of some volcanic soil, probably 

 as the result of a local lava flow in Tertiary time, evidence of which was 

 found on some basalt-capped hills near. The addition of a slight per- 

 centage of volcanic soil was sufficient to sustain the box trees, but not 

 to prevent the growth of Angophora lanceolata. 



A striking example of the regulating influence of geological forma- 

 tion on the flora in the same district is given by A. C. Barwick (2), where 

 he points out that the small isolated basaltic areas are known as clears, 

 in contrast to the much more dense growths on the surrounding sand- 

 stone. They are sometimes spoken of as box clears, owing to the 

 quantity of Eucalyptus hemipholia growing thereon. 



Although Angophora lanceolata is typical of the Hawkesbury sand- 

 stone around Sydney, it seems unable to withstand the cold of the Blue 

 Mountains above an altitude of about 3,000ft., which provides another 

 instance of the dominating influence of climate. As an equally interest- 

 ing example of geological influence, it is pointed out that A. lanceolata 

 crosses to the west of the main range through a low part of the Liverpool 

 Range, and is flourishing on a somewhat similar sedimentarv formation 

 along the northern part of the western slopes ; thus showing that the 

 question of aspect is not of paramount importance to this species. 



