54 



DISEASES OF TREES 



the entrance of air to the interior of the tree is ensured has yet 

 to be explained. The carbonic acid which is formed can 

 escape by the same way as the oxygen entered. To what 

 extent carbonic acid and oxygen when dissolved in water may 

 traverse the wood remains to be determined. 



FiG. n. Decomposition of oak by The'ephora Ferdix. a, tracheids containing a 

 few filamentous mycelia,and showing the perforations in the walls which these have 

 occasioned ; b, wood-parenchyma with starch-granules, the latter being in process 

 of solution, and having to a certain extent disappeared from the neighbourhood 

 of the cell-walls ; c, vessels containing hyphte ; d, sclerenchymatous fibres show- 

 ing filamentous mycelia and perforations ; e and /, tracheids which are com- 

 pletely isolated owing to the dissolution of the primary cell-walls ; the thickened 

 rings of the bordered pits are also found isolated between the tracheids. On 

 account of the organs being dismembered the openings into the bordered pits no 

 longer cross each other ; g, wood-parenchyma, completely dismembered and 

 almost entirely dissolved ; h, tracheid just before final disappearance ; z, scleren- 

 chymatous fibre much decomposed ; /6, a tracheid whose walls have become 

 fissured before being dissolved. 



In concluding these general considerations, I have still to 

 discuss the question whether any and, if so, what means are 

 at our disposal for combating the ravages of fungi. I am 

 convinced that every forester who has received a scientific 

 education will take a deep interest in obtaining a knowledge of 

 what tree-diseases are, and how they originate, even though it 



