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 de- 

 struction 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 thinning 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 ex- 

 terminated, and this they are wholesale. Out of 357 

 seedling-weeds growing together without any crowding 



