222 ON TREES. 



forewarned of the coming ruin. The disease which 

 causes the destruction takes place in the oak ; but 

 more frequently in the sycamore ; and most com- 

 monly of all in the ash. We will select this last tree 

 by way of elucidation. 



Often, when arrayed in all the bloom of vegetable 

 beauty, the ash tree is seen to send forth from its 

 bole, or from some principal branch, a small fungus, 

 which, during the summer, increases to a consider- 

 able size. It ripens in the autumn, and falls to the 

 ground when winter's rain set in. The bark through 

 which this fungus sprouted is now completely dead, 

 though it still retains its colour ; and that part 

 of the wood from which it proceeded is entirely 

 changed in its nature, the whole of its vitiated 

 juices having been expended in forming and nourish- 

 ing the fungus. Nothing remains of its once firm and 

 vigorous texture. It is become what is commonly 

 called touchwood, as soft and frangible as a piece 

 of cork, which, when set on fire, will burn like 

 tinder. In the mean time, the tree shows no sign of 

 sickness ; and its annual increase goes on as usual ; 

 till, at last, the new swelling wood closes over the 

 part from which the fungus had grown, and all 

 appears to go on right again. But, ere the slow 

 process arrives at this state, the titmouse or the 

 woodpecker will "have found an entrance, and a place 

 of safety for their incubation. They quickly per- 

 forate the distempered bark ; and then, the tainted 

 wood beneath it yields to their pointed bills, with 

 which they soon effect a spacious cavity. 



Here then we have the whole mystery unfolded. 



