FUNGOID DISEASES OF PLANTS 149 



There does not look to be much the matter with the 

 tree in the first instance, only that the leaves, instead 

 of being a natural green, present the appearance of a 

 silvery sheen, due to air spaces in the tissues, the cells 

 trjdng to elbow themselves away from one another, and 

 thus the leaves soon die. Presently the branches begin 

 to die and the tree really looks sickly. The final stage 

 takes place -within the trunk itself and results in a total 

 loss. (See Plate 35.) 



When the tree is dead, fructifications of this fungus 

 exhibit themselves on the surface of the bark. The 

 culprit is now exposed to view, and when young is purple 

 in colour and tough as leather, but during a dry speU 

 shrivels away. Wet weather, however, brings the fungus 

 to life again and causes milHons of spores to be released. 



This disease cannot be combated by any such means 

 as spraying, and consequently it is essential that a watch 

 should be kept for it and the silvering locahzed by cutting 

 off and burning the affected parts of the tree. Also, 

 needless to say, dead wood should be at once destroyed, 

 and dead trees, if they cannot be grubbed up, must have 

 their stumps fired with paraffin and covered with earth. 

 The fungus flourishes in damp situations, so that improved 

 drainage and tillage of soil will have the effect of dis- 

 couraging its activities. 



