PROCEEDINGS OF SECTTOX D. 477 



examination of the locality, however, discloses the fact that the southern 

 margin of this Syncarpia practically coincides with the southern edge 

 of the great Permo-Carboniferous coal basin which extends roughly 

 from the Clyde River northerly to the Hunter. The turpentine con- 

 tinues north of the Hunter, and may be found at intervals throughout 

 the north coast of New South Wales, extending also into Queensland. 



Now much of this northern formation is carboniferous, which, 

 geologically, is slightly older than the Permo-Carboniferous. but which 

 produces a flora somewhat similar. From the fossils which have been 

 collected on the country immediately south of the turpentine area the 

 formation appears to be Devonian — again older than the Carboniferous 

 — and it undoubtedly looks as if the geological formation has had all 

 to do with regulating the distribution of the species in this locaUty. 



Coming up along the south coast we find, at Milton, a group of 

 igneous rocks, including basalt and allied forms, and embracing an 

 area of about 15 to 20 square miles (6). Surrounding this is the sedi- 

 mentary formation of Permo-Carboniferous age, and it is remarkable 

 how the turpentine approaches the margin of the igneous area and 

 then stops abruptly. Some years ago I noticed an acre or so of sand- 

 stone, only slightly exposed, in a clear field near the centre of the 

 igneous formation, and, on drawing the attention of a local resident to 

 the fact, he at once pointed to a few turpentine trees about a quarter 

 of a mile distant, and expressed the opinion that the rock under them 

 was also sandstone, though none were visible. The incident demon- 

 strated that the turpentine was regarded as typical of the sandy area 

 in this district. 



As an evidence of the important influence of geological formation 

 on vegetation and the productiveness of the soil, it may here be noted 

 that if these volcanic rocks had not been exposed in the locahty the 

 district known as Milton would not exist, but in its place would be an 

 unbroken tract of uninviting sandstone country. 



Just westward of Sydney the Hawkesbury sandstone is covered 

 by the fine Wianamatta shale formation, which embraces a district 

 with its boundary just outside of Parramatta, Richmond, Penrith, 

 and Picton. Now. here again, we have a most interesting example of 

 geological influence on plant life ; for, on leaving the sandstone for the 

 shale, we step practically from one flora to another. Some species are 

 common to both formations, but numerically the sandstone is by far 

 the richer, and the general facies of the two floras is quite dissimilar. 

 Once more we find the Syncarpia vigilant in regard to any change in 

 geological formation, but here it compromises shghtly, and appears to 

 thrive best where the sandstone has a thin coating of shale. 



As the Wianamatta shales were originally deposited in a broad 

 basin it can readily be seen that near their margin they become shallow. 

 The result is that the turpentine in places extends some distance on 

 to the shale, and to the casual observer may be regarded as typical of 

 that formation ; but an examination of this particular district discloses 

 the fact that Syncarpia laurifolia forms a sort of fringe around it, and 

 its progress is arrested by the increasing depth of the original basin, 

 which places the influence of the sandstone beyond reach. It is of 



