162 EXPERIMENTS 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 are 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. 



