162 EXPEBIMENTS WITH PLANTS 



Jasmine, etc., are protected against such attacks by 

 poisonous substances; others by a bitter taste, such as 

 Chicory, Dandelion and Rhubarb. Immense damage 

 has resulted from Phylloxera, an insect which attacks 

 the roots of grape-vines in Europe. For some reason 

 the roots of native American grapes are not attacked 

 by the insect, and the European varieties ai-e therefore 

 grafted upon them. It is not known how the roots of 

 American vines protect themselves, but the great im- 

 portance of such protection is very evident. 



