INJURIES INDUCED BY PLANTS 



29 



remain alive. These, however, are in the same position as the 

 roots of a tree that has been felled that is to say, they can no 

 longer conduct nutritive substances to the leafy part of the 

 mistletoe, which must therefore die when its feeding-roots are all 

 confined to the bark. Its place is taken by numerous root- 

 shoots which arise from buds formed on the outer side of 

 those portions of the cortex-roots which are still alive. The 

 mistletoe represented in Fig. 2 is just such a root-shoot. These 

 shoots, which are represented in Fig. 4, form a new root-system 



FlG. 4. Part of the stem of a silver fir showing a group of mistletoe plants. The 

 bark has been removed from one side in order to show the position of the cortex- 

 roots and sinkers. 



of their own, and thus it happens that an old stem attacked by 

 mistletoe contains numerous young and old cortex-roots, as well 

 as old and young sinkers. In this way the tree comes to bear as 

 it were a plantation of mistletoes, which is constantly being re- 

 generated by the production of new root-shoots, and which is 

 always taking possession of a larger part of the tree. On old 

 silver firs and Scotch pines it is by no means rare to meet with 

 such mistletoe plantations a yard long and half a yard broad. 

 It ought to be mentioned that the living sinkers begin to die at 

 their apices (Fig. 3) whenever they become enveloped by the 



