THE DECAYED WOOD. 21 



The affected wood is also more darkly colored than normal sound 

 wood, and this undoubtedly helps to <iive the discoh^-ed appearance 

 on the exterior. It can not be said that these discolored spots 

 always have a direct relation to the season cracks, but tliis is very 

 often the case. Wliether the spots are a result of the season cracks 

 is uncertain, but in many instances at least they seem to be. 



INTERNAL APPEARANCE OF TIMBER. 



This fungus attacks coniferous wood wherever the conditions are 

 at all favorable for the growth of the fungus, and it soon reduces the 

 wood to a tlry, brown mass, retaining but little resemblance to its 

 normal appearance (PL III, fig. 1). The decay has been called a dry 

 rot. It has always been found that when fruiting bodies have been 

 formed at least a small portion of the wood has l)een completely 

 rotted. At first the tendency is to form small pockets of rotted wood 

 in the interior of the attacked timber, then to s})rea(l from these 

 into the adjacent wood, spreading longitudinally faster than radially. 

 The writer found that rot extended longitudinally in the wood from 

 the fruiting bodies at least a foot, and sometimes for t\\'ice that 

 distance, but commonly between tliese limits. 



In the early stages of decay the early spring wood of the annual 

 rings sometimes may be completely rotted and reduced to an amor- 

 phous powder, while the late summer wood, which is more compact, 

 is almost wholly unaffected. The amiual rings may then be very 

 easily separated from each other with the fmgers, and it is impossible 

 to cut a block of such wocxl out of the affected timber, owing to the 

 rings falling apart as soon as cut across. This peculiar action of 

 Lenzites sepiaria, the writer believes, is due simply to the structure 

 of the annual ring, which in some species of trees exhibits distinct 

 tliff'erentiation between the early, porous portion and the later, 

 more compact portion. Boiling tests made by the writer (1906) 

 showed conclusively that the lignm of the early wood is more easily 

 dissolved than is that of the late wood of the same annual ring, 

 where the two parts are at all distinct. The degree of tlifferentiation 

 in the annual ring seemed to be the controlling factor hi this differ- 

 ence in solubility of the lignin. Attention was called to the fact that 

 these tests furnish an ex})laiiation for the disintegration of the early 

 wood of the annual ring by certam wood-rotting fungi, while the 

 late wood is but slightly decayed. 



The affected wood assumes a shade of light brown, and small cracks 

 run irregularly across the wood fibers, indicating that considerable 

 shrinkage has been caused by the action of the fungus upon the wood 

 (PI. IV). The infections nearly always take place in season cracks, 

 as is ver}^ clearly shown by the position of the fruiting bodies (PI. 



214 



