WEEDS AND FUNGI 131 



blanks caused by the removal of the infected plants should be 

 filled up with some broad-leaved species. 



The Red -rot root -fungus (Pomes annosus or Trametes 

 radiciperdci). 



This fungus is very destructive to conifers. 



The infected trees appear very like those attacked by 

 the honey fungus, they turn yellow and die in the same 

 way. The mycelium, which will be found between wood and 

 bark, is however much more delicate and silky, and resembles 

 tissue paper. The fructifications are not formed above the 

 ground but on the roots, in masses like yellow or snow-white 

 grapes; sometimes the mass is bracket-shaped. 



Fig. 10. Fructification of Fomes annosus, Fries., on a Scotch pine root. 



(Reduced.} 



Other points of difference are that resin does not exude at 

 the roots of the trees in large quantities, and that in the rotting 

 wood are found black spots surrounded by soft white patches. 

 The rotting wood is at first violet and then of a brownish- 

 yellow colour. 



The disease spreads by the spores being carried about in 

 the fur of mice, and by infection of sound roots by contact 

 with those already attacked. Infected roots then rot, and the 

 rot spreads upwards into the stem. 



Isolation trenches are of little use with this disease, and the 

 only remedial measure which can be taken is to dig up all 



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