40 



Massee describes this canker as being " a wound-parasite, its spores germinat- 

 ing in the first instance on some wounded surface, and from thence invading the 

 healthy tissues. The bark is first attacked and destroyed, often cracking in a 

 concentric manner; afterwards the wood is also destroyed, the canker often com- 



A liiiiL liijc^ji-ii '.. ;th Nectiia Canker. 

 Note open wound with large callus edges. 



Black Rot Canker on apple branch. 

 (For description see page 42.) 



