DEFECTS AND UNSOUNDNESS. 77 



iii. Amount of Damage done to Timber by Decay. 



It is hardly possible to state which species of trees are more 

 liable to decay than others. In certain cases the question 

 arises as to the extent and stage of the decay, before the disposal 

 of the wood can be decided. 



Locality has far more influence than species on decay. There 

 are certain woods in which most of the spruce are suffering from 

 red-rot, and others where it is rare. Similar results occur in 

 the case of Scotch pine, for while in North Germany, fungus- 

 attacks on trees are common, they are scarcely known in the 

 greater part of South Germany. 



The Age of the woods is another cause of decay, and super- 

 annuated woods always contain more diseased trees than younger 

 woods. The mode of treatment which has been adopted, and 

 whether lopping, pruning or pollarding is allowed, is also of 

 considerable influence on the soundness of the wood. 



The difference in this respect between coppice and seedling- 

 plants is important ; aspen and alder coppice-shoots are fre- 

 quently decayed, whilst trees of these species sprung from seed 

 remain sound. 



Trees may be in very different stages of decay, from its first 

 appearance to utter disintegration of the tissues, and their 

 relative value under these different conditions will vary con- 

 siderably. Thus silver-fir and spruce logs left lying through 

 the winter get blue sapwood due to a fungus {Ceratostoma 

 jiiUferiim), and red stripes may appear on the surface of the logs. 



In such cases it is important to decide whether by proper 

 treatment the wood may not still be fit for use as timber. 

 Practical tests for this are found in examination of the ends of 

 the log, of its degree of hardness, dampness, odour, colour and 

 sound given out when struck with the butt-end of an axe. In 

 the case of standing trees, the appearance of the crown, branches 

 and stem may be used to determine their condition. 



The sections at the two ends of a log are often indices of the 

 state of soundness in the case of species subject to decay along 

 the stem. 



In many cases, the scent of the sawdust is an excellent guide to 

 the soundness of the wood; thus sound oakwood possesses the well- 

 known scent of tannic acid, whilst in the case of many diseases 



