A BED OF NETTLES. 115 



However, the sting itself, viewed philo- 

 sophically, is not without decided interest of 

 its own. It is one, and perhaps the most 

 highly developed, among the devices by which 

 plants guard themselves against the attacks 

 of animals. Weeds or shrubs with juicy 

 tender leaves are very apt to be eaten down 

 by rabbits, cows, donkeys, and other herbi- 

 vores. But if any individuals among such 

 species happen to show any tendency to the 

 development of any unpleasant habit which 

 prevents the herbivores from eating them, 

 then those particular individuals will of course 

 be spared when their neighbours are eaten, 

 and will establish a new and specially pro- 

 tected variety in the course of successive 

 generations. It does not matter what the 

 peculiarity may be, provided only it in any 

 way deters animals from eating the plant. 

 In the arum, a violently acrid juice is se- 

 creted in the leaves, so as to burn the mouth 

 of the aggressor. In the dandelion and 

 wild lettuces, the juice is merely bitter. In 



I 2 



