Friends and Foes 301 



in a small plot of ground, Mr. Darwin found that 295 

 were destroyed, mainly by slugs and insects. 



From the point of view of the destroyed — the victims 

 — these creatures were undoubtedly foes ; but from that 

 of the survivors they were as certainly friends, for the 

 latter would grow up all the more vigorous for having 

 plenty of space. 



But if slugs and insects were allowed to multiply 

 without check, they would become foes and nothing 

 else, and would end by eating up every green thing. 

 There are checks upon their increase, however ; and 

 besides this, many plants are to some extent protected 

 against them, as otherwise certain species might be 

 exterminated altogether. 



Plants like the grasses, which bear vast quantities of 

 seed, are protected by their very numbers, and can 

 well afford to be eaten, if but a small proportion be 

 allowed to perfect and disperse their seed ; but others, 

 less prolific, are guarded in various ways, being made 

 either disagreeable or difficult of approach. 



The whole of the Gentian order, for example, are so 

 extremely bitter, that they are seldom touched even 

 by caterpillars ; and the Eschscholtzia, which is of 

 another order, is also so intensely bitter as to be more 

 avoided by slugs and the like than any other plant, it 

 is said. Even Eschscholtzias are, however, a good 

 deal bitten at times, probably by earwigs, but this may 

 be owing to drought and consequent scarcity of vege- 

 table matter, as it is not a common occurrence. It is 

 at least something to be proof against certain classes 

 of enemies; and no plants are defended against all, 

 since they are intended to be eaten, though not 

 exterminated. 



