G4 Dr A. MiiiTay on ihe Jiiflucncc of Rochs 



the more genial climate. Climate, indeed, may he called the 

 master regulator of vegetables. On this account, when impres- 

 sion of vegetables, with a tropical aspect, are met with in the 

 south of Scotland, their dissimilarity to the species found at the 

 present day in the same situation, is attributed, not to the dif- 

 ference of rock, but to the change which, in these latter times, 

 our climate must have undergone. Let any change of place be 

 made, short of that which is accompanied by a material al- 

 teration of climate, and the prevailing features of vegetable 

 nature do not undergo a change. Every thing around us may 

 have become different, while the native plants continue, in ge- 

 neral, the same ; and, more than any thing, bring back to me- 

 mory the region which we have left. On the other hand, let 

 us remove to a remote latitude, or even a different elevation, 

 and however similar may be the rocks before us, a different 

 creation of vegetables prevails. It is well known that the gra- 

 nite in the higher parts of the Alps is clothed with a vegetation 

 different from that which covers the same rock in Cornwall ; 

 and no one will deny, that the plants growing upon the trap of 

 St Kilda, are different from those which are found in a trap 

 district of Hindostan. 



In conclusion, it may be laid down as a general rule, that ve- 

 getable species are not limited and determined by the subjacent 

 rocks ; but to this there may be a few exceptions. Thus, it is 

 certain that plants must be affected by rocks which influence the 

 moisture of the soil ; and, considering the peculiar and energetic 

 properties of lime, it is not an improbable guess that it may be 

 eventually established that certain plants are confined to the 

 limestone rocks. 



The title of this paper has been limited to the supposed in- 

 fluence of roclx's upon native vegetables ; as it is not intended to 

 discuss, in any complete manner, the question as to relations 

 subsisting between soils and plants — a subject far more difficult 

 than the other to submit for examination, on account of the very 

 great variety of combinations which the ingredients of soil are 

 capable of forming. It may be permitted me, however, to say 

 briefly, that, in all probability, the native plants of any given 

 region will, when other circumstances are equal, grow and pros- 

 per in any soil, some exceptions being necessary, chiefly on the 

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