DISEASES OF TREES 



FIG. 73. A leaf of P. ni^ra 

 affected by Exoascus Pofuli. 



FlG. 74. Malformation 

 of the fruit of P. 

 tremula, due to E. 

 Populi. 



FIG. 75. A witches' broom of the hornbeam induced by Exoascus Carpini. 

 Half natural size. 



