DISCOLOURATION. 145 



or silver-fir, but somewhat rarer in the Scots pine. These 

 streaks occur in two forms. Bed streaks appearing simul- 

 taneously from the external surface towards the pith, through 

 the whole length of a log, are caused if a barked log with 

 superficial air-cracks is floated or rafted, or placed in a wet 

 place. It is especially the air-cracks from which the red 

 streaks start, that induce the growth of fungi the nature of 

 which has not yet been determined. The longer the influence 

 of the unfavourable environment continues, the deeper goes 

 the mischief, which first affects the sapwood. Such wood is 

 more or less unserviceable as timber, according to the extent 

 of the decay to which it is subject : Hartig and Sepp have 

 written on the red streaks in the wood of spruce and silver-fir 

 from the Bavarian Forest, but the above remarks are founded 

 chiefly on Mayr's observations. 



A second form of red streakiness starts from a centre 

 of decay, either in the stump or roots, or from the occluded 

 snags of dead branches. It extends both up and down the 

 stem. 



Blue-streaks appear in the sapwood of logs of the Scots 

 pine when they have been exposed for some time to damp, and 

 a fungus, CerdtoHtonia }>il>t'<'ra, has gained admission to the 

 wood owing to injuries to the bark. The commencement of 

 this disease affects only the colour but not the hardness of the 

 wood, though Schwappach and Eudeloff have shown that its 

 elasticity is thus impaired. 



Black-streaks in the sapwood of spruce and silver-fir, so 

 that even the whole of a cross-section of the sapwood may 

 become completely black, occur in logs which have remained 

 lying for some time unbarked. When spruce logs are felled 

 and stripped of bark in summer, drops of turpentine exude 

 from numerous horizontal resin-ducts, and, between these 

 drops, the wood in a few days becomes grey and gradually 

 blackens, so that it appears to be spotted. The fungus that 

 causes this penetrates the borings of Tomicas lineatus, from 

 which also black streaks enter in the wood. 



Dark-blue streaks are the first symptoms of the destruction 

 of wood by two most dangerous fungi, Forties annosus and 

 honey-fungus (Armillarea mdlea), both of which cause 



F.U. L 



