Section D.— BIOLOGY. 



1.— CLIMATIC AND GEOLOGICAL INFLUENCE ON THE 

 FLORA OF NEW SOUTH WALES. 



By R. H. GAME AGE, F.L.S. 



[With Map.] 



Of the various influences which affect the growth of plants two of 

 the most important are those of cUmate and geological formation. 

 Irrespective of these, the questions of rainfall, aspect, moisture, and 

 shelter operate largely in the regulation of plant life. 



Dealing first with geological considerations, it is found that, broadly 

 speaking, the rocks which produce distinct lines of cleavage in the flora 

 may be divided into two classes, viz., igneous and sedimentary ; although 

 the floras produced on fine and coarse forms of each section sometimes 

 show a marked divergence. Metamorphic schistose rocks seem to pro- 

 duce floras with affinities to those of sedimentary areas, rather than 

 typical igneous formations. An instructive paper by A. G. Hamilton (5) 

 gives the flora on the basalt of Mount Wilson and adjoining sandstone. 



Among the igneous rocks, a gradation exists in the floras found on 

 formations derived from fine basalts (basic) on the one hand to coarse 

 granites (acid) on the other. A somewhat similar gradation occurs among 

 sedimentary rocks, as exemplified by the changes between fine shales and 

 coarse sandstones. The points at which the floras of igneous and sedi- 

 mentary formations more nearly approach each other are between the 

 coarse granites and the sandstones. Nor is this remarkable, seeing that 

 the sandstone areas are merely redistributed disintegrated igneous rocks, 

 and are in many instances composed of quartz derived from coarse 

 granite, porphyry, &c. Should the granite contain a fair percentage of 

 hornblende, ferro-magnesian silicates, as when biotite, &c., are present, 

 the flora on such a formation departs from that of a sandstone area, 

 and, provided moisture is present, becomes more luxuriant. An in- 

 stance of this may be seen at Mount Dromedary, on the south coast, 

 from which locality the rock has been examined by Mr. G. W. Card, 

 A.R.S.M. (3). I recently drew attention (4) to the great similarity 

 between the flora of an area of decomposed granite near the Wombeyan 

 Caves and that of the Triassic sandstone around Sydney and on the 

 Blue Mountains, the features being accounted for by the suggested 

 common origin of both formations. 



Many plants, however, will not sharply discriminate between 

 geological formations, being probably affected by other factors, and 

 the subject becomes difficult when an attempt is made to enumerate 

 the species which it is thought may be confined to either an igneous 

 or sedimentary area. Although plants may in some localities be 



