INJURY CAUSED BY NON-PARASITIC ORGANISMS 59 



INJURY CAUSED BY NON-PARASITIC OR UN- 

 DETERMINED ORGANISMS 



Lichens on fruit-trees. Very frequently the trunk and 

 branches of fruit-trees are covered with a dense growth of 

 lichens of various kinds, which while admittedly adding to 



FIG. 7. Usnea barbata and Ramalinafraxinea, lichens 

 growing on branch of apple-tree. Reduced. 



their artistic appearance, are in other respects injurious, for 

 although not true parasites, their presence prevents the bark, 

 more especially of the younger branches, from performing its 

 functions, and in addition forms a shelter for many kinds of 



