FESTS 75 



but it is properly restricted to the work of the par- 

 ticular fungus named above. The bark on the stem 

 or branches, especially in the fork of a branch, appears 

 to be eaten away, exposing the wood beneath, the 

 wound being surrounded by a thick rugged mass of 

 bark : gradually the branch dies, and, in the case of 

 a young branch, the spread of the disease is rapid, 

 the outer bark along the whole branch becoming 

 detached, thus giving it a light brown appearance. 

 The canker fungus is a wound fungus, and gains 

 entry only where the outer bark is punctured, as, for 

 instance, where the tree has rubbed against the stake, 

 etc., where the pruning knife has been at work, or 

 where the bark has been injured by woolly aphis, 

 hail, etc. The fungus has two forms of fruit, both of 

 which may be found in the wounds — (i) minute white 

 specks appearing in the late summer ; (2) bright red 

 little balls appearing in the spring. These red balls 

 are often taken for red spider eggs ; but the eggs are 

 of a more shiny red colour, and are much more 

 easily removed from the trees. A magnifying glass 

 is necessary for distinguishing the fruit bodies of 

 the fungus. Varieties of apples differ as to their 

 susceptibility to canker (though locality affects their 

 behaviour), those with the thinnest and softest bark 

 being generally the most susceptible. 



Remedies. — No real remedy is known, but the 

 spread of the disease may probably be checked by 

 spraying the trees, or painting the wounds, with 

 copper sulphate (8), or potassium sulphide (24), as 

 soon as the leaves are off the trees : and, when winter 

 washing the trees, a wash containing a fungicide 



