THE BLUEING OF CONIFEROUS TIMBER. 87 



for under these conditions the supply of air in the wood is 

 reduced to a minimum. 



It is well known that timber stacked in the forest for some 

 time is especially liable to become infected, and this is what 

 the above results lead us to expect, on the assumption that 

 some at least of the spores of the fungi concerned are air-borne. 

 Timber stored in a drying shed provided with a roof but open 

 at the sides would be less likely to become infected, especially 

 if the pieces were stacked so as to allow of the passage of 

 a free current of air. Under these conditions drying would not 

 only proceed more rapidly and the time during which infection 

 could take place would thus be diminished, but the timber 

 would not be wetted by rain and the germination of spores 

 would probably not go on readily on the dry surfaces. There 

 is no information available as to the minimum amount of water 

 which must be present for growth of the mycelium in the 

 wood, but thoroughly seasoned timber does not usually become 

 infected. Professor Home ^ is of opinion that if the moisture- 

 content of the timber is reduced by air drying under protection 

 from the weather no appreciable "blueing" will occur, even 

 if the timber is subsequently exposed to the weather for a short 

 period during the construction of buildings. 



In any consideration of the circumstances under which 

 infection of stored timber may take place, it is necessary to 

 remember that the presence of spores is essential for the develop- 

 ment of the disease. These would undoubtedly be present 

 in the forest area, but would probably be diminished in number 

 away from the vicinity of infected trees, and might even be 

 altogether absent where building operations were taking place, 

 e.g. in towns. In this connection, however, an observation 

 made by Hubert- in a recent paper is of interest. This writer, 

 describing his investigations into the length of time during 

 which the mycelium can remain in a living condition in timber, 

 states that he made cultures from fragments of blue-stained 

 wood taken from a piece of structural timber which has been 

 in a factory building for seven years. The timber in this 

 building was shipped green from the mill and put in place 

 during rainy weather. 



^ " Experiments on the Mechanical Properties of Scots Pine.'' Paper read 

 before Section G of the British Association, Edinburgh, 1921. 



- " Notes on Sap Stain Fungi," Phyiopatk, xi., 5, pp. 214-224, 1921. 



