Chap. III.] STRUGaLE FOR EXISTENCE. 87 



is abounding in individuals, even on the extreme verge 

 of their range. For in such cases, we may believe, 

 that a plant could exist only where the conditions of 

 its life were so favourable that many could exist to- 

 gether, and thus save the species from utter destruction. 

 I should add that the good effects of intercrossing, 

 and the ill effects of close interbreeding, no doubt come 

 into play in many of these cases; but I will not here 

 enlarge on this subject. 



Complex Relations of all Animals and Plants to each 

 other in the Struggle for Existence. 



Many cases are on record showing how complex and 

 unexpected are the cheeks and relations between or- 

 ganic beings, which have to struggle together in the 

 same country. I will give only a single instance, which, 

 though a simple one, interested me. In Staffordshire, 

 on the estate of a relation, where I had ample means 

 of investigation, there was a large and extremely barren 

 heath, which had never been touched by the hand of 

 man; but several hundred acres of exactly the same 

 nature had been enclosed twenty-five years previously 

 and planted with Scotch fir. The change in the native 

 vegetation of the planted part of the heath was most 

 remarkable, more than is generally seen in passing from 

 one,j:wute different soil to another: not only the pro- 

 pojrtional numbers of the heath-plants were wholly 

 chianged, but twelve species of plants (not counting 

 grasses and earices) flourished in the plantations, which 

 could not be found on the heath. The effect on the 

 insects must have been still greater, for six insectivor- 

 ous birds were very common in the plantations, which 

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