WOUNDS 



243 



are usually smaller, but also because the wounds have the 

 opportunity to become impregnated with resin before the 

 season when a higher temperature favours the formation of 

 wound-rot, or the germination of the spores of parasitic fungi. 



Should parasites gain an entrance, decomposition spreads 

 rapidly in all directions, and results in the destruction of the 

 tree. In other cases the wound-rot merely induces the inner 

 layers of wood to become brown, without, however, attacking the 

 wood that is formed in succeeding years. Should the wound 

 remain long open, wound-rot may assume very serious propor- 



FIG. 138. Transverse section 

 of a pine-stem showing a 

 wound caused by the peeling 

 of red deer over which a 

 callus has formed, but which, 

 after twenty-four years, is 

 not yet quite closed. One 

 third natural size. 



FIG. 139. Transverse section of a spruce-stem 

 showing three wounds due to the barking of 

 game. One half natural size. 



tions. As a rule it ascends in the stem only to the height of a 

 few yards, so that, when this is the form of " Red-rot," the 

 timber is sound after the removal of a few short lengths. As 

 the spot where the bark has been removed offers the least resist- 

 ance, it is evident that should the tree be loaded with snow it 

 will break most easily at that point. 



BARKING BY MICE 



The wood-mouse (Mus sylvaticus] and the field-mouse (Arvicola 

 arvalis 1 } especially injure young dicotyledonous trees by gnaw- 



1 A. arvalis is not a native of Britain, but other species of the same 

 genus do considerable damage to trees in this country. Trans. 



R 2 



