212 DISEASES OF TREES 



completely fills up the lumina of the tracheides. On account 

 of the mycelium assuming a brown colour when in this con- 

 dition, it makes the portion of diseased wood which it infests 

 appear to the naked eye like a black line. As this kind of 

 mycelium soon dies off and is dissolved, being replaced by a 

 delicate filamentous mycelium, it seldom happens that the zone 

 which it occupies exceeds the breadth of 3 4 tracheids. The 

 walls of the elements of the wood afterwards display a cellulose 

 reaction, and speedily dissolve from the lumen outwards. 



On account of the trees drying up, after the rhizomorphs have 

 spread from the point of infection on the roots into the stem, and 

 again from the stem into the hitherto sound roots, decomposition of 

 the stem usually ceases before the mycelium has advanced from the 

 alburnum into the duramen. It is only in the stool and roots 

 that decay rapidly spreads throughout the whole of the wood. 



The practical preventive measures to be enforced in the 

 case of this parasite are the same as those which I have 

 already recommended for Trametes radiciperda (see pp. 190-91). 



THE DESTRUCTION OF STRUCTURAL TIMBER BY FUNGI 



Although, strictly speaking, the diseases of felled timber 

 should not be discussed in a text-book of the diseases of trees, 

 still an abbreviated summary of the results of my investigations 

 on this subject may not be altogether out of place. 1 



As regards the management of squared and round timber 

 before it is utilised that is to say, in the forest and during 

 transport one should in titittirst place take all reasonable 

 precautions to see that, after^Spg, only sound wood is retained 

 as structural timber. Of cour^it is always possible that now 

 and again a log or beam will be retained that turns out to be 

 diseased during subsequent manipulation. This may be due to 

 the fact that a parasite which has entered through a branch- 

 wound has not spread up or down to one of the sectional 

 surfaces, so that it is impossible to recognize the destructive 

 effects of the fungus when the timber is despatched. It is often 



1 Der dchte Hausschwamm (Merulius lacrymans} (Berlin, Springer, 1885), 

 and Die Rothstreifigkeit des Bate- und Blochholzes und die Trockenfdule. 

 Allg. Forst- undJagd-Zeit.* November 1887. 



