FIG. 27. Canker fungus spreading down from a branch. 

 This was photographed from a living specimen . The dark- 

 coloured cortex near the branch is dead. The lighter 

 coloured, above and below this, is alive. 



FIG. 28. Spread of fungus down the branches. This 

 stem was taken from a young tree which had been felled 

 and allowed to lie in the wood for a few months. 



