TIMBER FUNGI. 207 



to segregate by ditching trees or groups which are infested wirh root- 

 rots such as Armillaria, but we have not yet come to hold our forest 

 trees worth that amount of trouble. The orchardist or landscape gardener 

 may prune his trees very carefully so that the wounds will heal over 

 quickly, but the forester has to leave this process to the forces of 

 nature, and the work is very crudely done, in most cases. 



The greatest fight against fungi must be made with a view to pre- 

 serving the life and lengthening the service of the wood that we put 

 in exposed situations. To this end a number of so-called "preservative 

 treatments" are at present commanding the attention cf the foresters, 

 or more accurately, the people who are using the timber; engineers 

 of construction, railroad companies, etc. The following discussion of 

 the character of wood and the habits of wood-rotting fungi, from 

 Freeman, will throw some light on the subject: 



The cell wall of wood in the young stages is v/hitish and not 

 particularly resistant, for it is a cellulose wall. Later new substances 

 are added which collectively are known as lignin, and the tissues then 

 become v;oody. Cellulose membranes are pierced by fungus threads 

 in a purely mechanical fashion, just as one would force a pin or needle 

 through them. Wood membranes offer considerable resistance to most 

 fungi, but some of them have solved the problem of penetrating these 

 walls. Such are the wood-destroying fungi already mentioned. The 

 threads of these parasites exude certain chemicals which are able to 

 attack the lignin of woody tissues and dissolve out this lignin. These 

 cell-walls now have the same chemical constitution that they had before 

 they became lignified. But the fungus is also able to attack the cellulose 

 wall, and the result is a more or less complete breakdown of the walls. 

 The wood crumbles easily and can be converted into punk. From the 

 points of contact the dissolving substance spreads over the cell wall, 

 completing the rotting process in that vicinity. 



Fungi have different methods of attacking and rotting woods. Certain 

 wood-rotting fungi can be determined by the kind of rot which they 

 produce. The wood-rot, therefore, often gives very definite symptoms 

 of a determinable disease. 



The study of wood-rots is receiving considerable attention at the 

 present time on account of its vast importance economically. To realize 

 this importance, one has but to think of the great losses sustained 

 yearly by the decay of mine-timbers, house-foundation and cellar timbers, 

 railroad ties, paving blocks, fence posts and rails — in fact, timbers 

 wherever air and moisture can reach them. The creasoting of pave- 

 ment blocks and tarring of cedar posts are attempts to aid the wood 

 in resisting the attacks of fungi. Tar and creasote are substances 

 in which the fungi cannot live, and their presence protects the wood. 

 But as soon as the substances are washed olf, the fungi commence their 

 attack. What is wanted is some substance which when deposited in 

 the wood will prevent the entrance of fungi and which will not readily 

 leach out into the soil during heavy rains. 



Seasoning of timber is an important factor; green timber contains 

 more moisture, which is directly favorable to fungus growth. 



The various methods of treating timber consist entirely of impreg- 

 nation processes. Chemical compounds in solution or emulsion are 

 forced into the timber or boiled in, so that they permeate the whole 

 timber, or at least the surface portions. These substances must be 



