390 NOTES ON NATIVE FLORA OF NEW SOUTH WALES, IV., 



speaking of the Italian flora says : — " He notes a change from a 

 central European to a Mediterranean flora independent of 

 climate. The occurrence of the Mediterranean flora he considers 

 to depend not so much upon the climate as upon the nature of 

 the surface rocks." 



In New South Wales alone we have innumerable instances 

 where the flora changes with a distinct line of cleavage, but in 

 most of such cases it is at the meeting of igneous and sedimentary 

 formations. In the locality under discussion we have sandstone 

 and shale, which are both sedimentary. But there are, at a 

 rough estimate, probably twenty to thirty per cent, of the plants 

 growing on the Hawkesbury Sandstone which do not occur on 

 the Wianamatta Shale, excepting around the fringe or where the 

 shale is shallow and the influence of the sandstone operates. 

 Two well known instances in the case of large trees may be 

 quoted, viz., Eucalyptus corymbosa Sm., the well known Blood- 

 wood, and Angophora lanceolata Cav., the smooth-barked Apple 

 or so-called Red Gum, both of which are common on the sand- 

 stone, but practically never on the deep shale. On the other 

 hand, the common Box around Parramatta and Penrith, Euca- 

 lyptus hemiphloia F.v.M., is abundant on the Wianamatta Shale, 

 but rarely, if ever, occurs on the Hawkesbury Sandstone. Some 

 of these species are probably as ancient as any of the genus 

 Eucalyptus, and have had thousands of years to spread only a 

 matter of a few yards on to the adjoining formation without 

 having done so. Further enlightenment in regard to plant food 

 may make the reason apparent. 



Tracts of isolated but similar vegetation are not uncommon, 

 and an examination of the surrounding country in many cases 

 discloses the fact that these particular floras are growing on the 

 same geological formation which was formerly more extensive, 

 but in intervening areas has been removed by denudation. The 

 presence of trees in distant situations may often be explained by 

 an investigation of former conditions and an imaginary recon- 

 struction of the old land-surface in the locality; or, in other 

 words, outliers may often be more satisfactorily accounted for as 

 ancient remnants than as recent extensions. 



