432 



I'ltOTKCTION ACALVST FUXCJI. 



appear in the soil, seldom deeper than four inches, that are 

 termed rhizomorphs. These latter are persistent mycelial 

 hyphae like sclerotic fibres, and resemble branching roots ; 

 they sometimes anastomose. "White ribbon-like hands of 

 mycelium are formed between the bast and sapwood and in 

 hollows in the dead bark and bast, and often spread like a 

 net ; mycelial strands which pass into the soil from these 

 white bands are round and dark-brown rhizomorphs, which 

 may also develop between the wood and the cortex, but are 

 then flat. 



Fig. 208.— EigUt-years-old Scots pine killed by A. mellca, Vahl. a Sterile rhizo- 

 morpliie straudy. b and c Fertile ditto ; some of the sporophores are abortive. 

 (I Sporophores spriugiug from mycelia under the bark. {Reduced.) 



Plants which have been attacked eventually die, and when 

 young generally in the first year of the disease. If the dead 

 plant be examined microscopically it will be found that the 

 bast and cambium have been destroyed, the resin-ducts are 

 full of hyphae and enlarged and deprived of resin ; fine hyphae 

 also proceed along medullary rays towards the centre of the 

 tree. Starch is transformed into turpentine which flows from 

 the tree. 



