160 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



be underground, and it is important to be able to 

 distinguish such forms in the absence of the fructifi- 

 cations. 



The external symptoms of the disease, where young 

 trees are concerned, are similar in both cases. In a 

 plantation at Freising, in Bavaria, I have been shown 

 young Weymouth pines (P. Strobus] attacked and 

 killed by Agaricus melleus. The leaves turn pale and 

 yellow, and the lower part of the stem the so-called 

 "collar" begins to die and rot, the cortex above still 

 looking healthy. So far the symptoms might be 

 those due to the destructive action of other forms of 

 tree-killing fungi. 



On uprooting a young pine, killed or badly attacked 

 by the Agaric, the roots are found to be matted 

 together with a ball of earth permeated by the resin 

 which has flowed out : this is very pronounced in the 

 case of some pines, less so in others. On lifting up 

 the scales of the bark, there will be found, not the 

 silky, white, delicate mycelium of the Trametes, but 

 probably the dark cord-like rhizomorphs : there may 

 also be flat white rhizomorphs in the young stages, 

 but they are easily distinguished. These dark rhizo- 

 morphs may also be found spreading around into the 

 soil from the roots, and indeed they look so much 

 like thin roots that we can at once understand their 



