Minnesota Plant Diseases. 



249 



under conditions normal to other spores. It has therefore been 

 recommended that such substances as furnish alkaline materials 

 be not brought unnecessarily into contact with structural tim- 

 bers. The fruiting body has an agreeable odor when young 

 but when old and in the stages of decay emits foul odors and in- 

 jurious gases and an excessive amount of water may be exuded 

 by the diseased timbers. 



Fig. 122. — The dry-rot fungus (Merulius lacrymans). Later decay stages than that shown 

 in Fig. 121. From the board shown on the left, the mycelial felt has been removed 

 and the checked portion of the board is seen. This appearance is caused by the 

 drawing of the tissues in drying after the decay has been well started. The removed 

 mycelial felt is shown in Fig, 5. The board shown on the right is in a still further 

 stage of decay and the wood under the mycelium is reduced to friable punk. Original. 



As has already been stated, infection of timbers does not 

 usually take place in the forest. It may occur where old timber 

 is stored with fresh lumber or where old timber is used in the 

 building of a new house. Workmen may carry spores on their 

 clothing or tools and thus cause an infection of timbers. The 



