STRUGGLE FOR EXISTENCE U75 



its preservation. Thus we can easily raise plenty of 

 corn and rape-seed, etc., in our fields, because the 

 seeds are in great excess compared with the number 

 of birds which feed on them; nor can the birds, 

 though having a superabundance of food at this one 

 season, increase in number proportionally to the 

 supply of seed, as their numbers are checked during 

 winter; but any one who has tried knows how 

 troublesome it is to get seed from a few wheat or 

 other such plants in a garden : I have in this case lost 

 every single seed. This view of the necessity of a 

 large stock of the same species for its preservation 

 explains, I believe, some singular facts in nature, 

 such as that of very rare plants being sometimes ex- 

 tremely abundant, in the few spots where they do 

 exist; and that of some social plants being social, that 

 is abounding in individuals, even on the extreme 

 verge of their range. For in such cases we may be- 

 lieve that a plant could exist only where the condi- 

 tions of its life were so favorable that many could 

 exist together, and thus save the species from utter 

 destruction. I should add that the good effects of 

 intercrossing, and the ill effects of close interbreed- 

 ing, no doubt come into play in many of these cases. 

 Many cases are on record showing how complex 

 and unexpected are the checks and relations between 

 organic 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 T 

 had ample means of investigation, there was a large 

 and extremely barren heath, which had never been 



