THE CULTIVATION OF THE OAK. 153 



wood-pigeons and other birds. In the north of Europe 

 the young plants suffer terribly from the ravages of a 

 fungus named Rosellinia, the mycelium of which sends 

 its branches into the roots and kills them, consequently 

 entailing the death of the plant. The larvae of various 

 insects also damage the roots and bring about injuries 

 which may prove fatal. Cynips corticalis produces galls 

 on the lower parts of the stems. 



When the plant has passed into the condition of a 

 sapling its dangers are for the most part of quite other 

 nature, the injurious fungi especially being different. 

 The chief diseases of the roots now arise from their 

 spreading into unsuitable soil, the drainage of which 

 may be incomplete, and thus bring about a sodden, acid, 

 ill-aerated condition. The want of oxygen and the low 

 temperature combine to kill the root- hairs and young 

 rootlets, and the leaves above part with their water 

 faster than it can be supplied from below, and they 

 turn yellow and die off, the branches dry up, and the 

 tree dies. 



Other dangers arise from the persistent overshadow- 

 ing of other trees, which slowly kill the young oaks by 

 depriving their leaves of light ; the offending trees 

 playing the same inimical part, in fact, that grass and 

 weeds, etc., play towards the small seedlings. Or the 

 roots may be too thickly set in the soil if the trees are 

 too crowded, and each suffers from over-competition 

 with others. 



Much mischief is effected by the attacks of insects 



