THE ENEMIES OF ENGLISH WOODLANDS 307 



but the most common and frequent origin of the disease 

 must be attributed to the soil. 



THE HONEY FUNGUS (Agaricus melleus). 



This is another of those facultative fungi which can be 

 either a parasite or saprophyte, as circumstances permit. 

 Probably its true character is that of a saprophyte on 

 hardwoods, and it attacks conifers in order to make the most 

 of its time. Its life-history is one of the most interesting 

 amongst the fungi with which the forester has to deal, for 

 its marvellous adaptation to environment would almost lead 

 one to believe that it possessed reasoning powers above the 

 average amongst members of the plant-world. According to 

 Hartig, the spores of the fungus are distributed by wind or 

 other agencies in autumn, and, upon these germinating, the 

 root-like mycelium is formed, which in one form or another 

 is one of the characteristic features of the organism. This 

 mycelium finds its way to the roots of some tree susceptible 

 to attack, such as an old and decayed hardwood, young Scots 

 fir, or other conifer, and then proceeds to develop beneath 

 the bark of its host. In its early stages, and when a plenti- 

 ful food supply is present, this mycelium is a pure white 

 felted mass, which completely fills the space between wood 

 and bark. But when food is scarce, as on wood already 

 dead, the mycelium assumes the character of brown, rope-like 

 threads, which are known under the name of " rhizomorphs," 

 and which carry the mycelium over sterile spots until it 

 again reaches more favourable material. These rhizomorphs 

 ramify and spread beneath the bark, in much the same way 

 as ivy will cover a stem externally, and they may be found 

 running up the dead tree to a considerable distance from the 

 ground. It can also make its way through soil, along the 

 underground face of a wall, between boards, and along or 

 through any other crevice or medium which is dark and 

 moist. In a freshly attacked tree this mycelium sends out 

 hyphse into the medullary rays of the wood, extracts the 

 nutritive materials they contain, and in conifers destroys 

 the parenchyma surrounding the resin canals, and allows the 



