CHAPTER XX 



FRIENDS AND FOES 



From one point of view all animals, with the exception 

 of a few insects, may be looked upon as enemies of the 

 plant-world, since they either themselves feed upon plants, 

 or live on others who do. But this would be a very 

 partial view of the matter, even where the destruction is 

 complete; for it is a positive benefit to the race that the 

 greater number of seedlings, as well as seeds, should be 

 devoured, or otherwise removed, since without this thin- 

 ning of their numbers none could come to perfection. 



Linnaeus calculated that any one annual which pro- 

 duced but two perfect seeds — its descendants doing the 

 same every year — would have increased to a million in the 

 course of twenty years. Now all annuals do considerably 

 more than this as a rule; and as they do not increase at 

 an alarming rate, it is evident that their existence must in 

 many instances be cut short, at one time or other of their 

 career. 



Plants have many and various enemies which attack 

 them at different stages of their lives, but it is chiefly 

 while they are seedlings that they are altogether extermi- 

 nated, as they often are wholesale. Out of three hundred 

 and fifty-seven seedling weeds growing together without 

 any crowding in a small plot of ground, Mr. Darwin 

 found that two hundred and ninety-five were destroyed, 

 mainly by slugs and insects. 



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