148 TIMBERS AND THEIR USES 



is also an enemy of Conifers. This fungus is 

 very similar to the Polyporus, but its spore- 

 bearing organs, instead ojE taking the form of 

 aerial brackets, are subterranean plates attached 

 to the roots of the host. A tree attacked by T. 

 radiciperda is easily recognized by its pale yellow 

 leaves which soon fall and by the death of the 

 lower part of the stem, though higher up it 

 appears quite normal. The mycelium travels 

 up the tree in the cambium of its host, sending 

 branches in all directions into the wood and 

 rapidly reducing it to a rotting mass. From time 

 to time the mycehum breaks out from the bark 

 and forms the spore-bearing organs, yellowish 

 white plates, perforated by innumerable minute 

 pores in which the spores are found. 



The diseased wood presents a very charac- 

 teristic appearance. Of a yellowish brown 

 colour, it is spotted here and there with oval 

 white patches, to each one of which there is a 

 black centre. 



One of the worst of all parasites of hving trees 

 is the so-caUed Larch disease or Larch canker, 

 Peziza WillJcommii. The causative fungus pro- 

 duces dead, sunken patches on the bark of its 

 host. Below these patches, no wood growth 

 takes place. From the surface of the sunken 

 areas the spore-bearing organs arise ; they are 

 small egg-cup-shaped structures, greyish without 



