io8 MOUNTAIN AND MOORLAND 



seen not a ring, but a solid circle, so to speak, with the 

 grass thicker and greener than beyond its bounds. 

 The explanation of fairy rings is not difficult. One 

 starts with a stalked Fungus like the Common Mush- 

 room, which is so palatable, or with the Fly Agaric, 

 which is so poisonous. Both are common causes of 

 fairy rings. The spores are scattered in a circle 

 around the original clump; they sink into the soil and 

 form an underground circle of spreading white 

 threads. These are practically perennial and extend 

 outwards into new territory. They may also give 

 rise to more Mushrooms or Fly Agarics, which pro- 

 duce more spores; and as these are scattered and 

 develop the ring of white threads expands. Now the 

 white threads (technically called " hyphse ") which 

 branch in the soil absorb some of the organic matter 

 of vegetable mould, and supply the above-ground 

 parts with all their food; they exhaust the available 

 materials, so that for the time being no more threads 

 can develop there; the scattered spores will develop 

 only in the unexhausted soil to the outside of the 

 spreading ring. So the ring is formed, the difference 

 in the colour of the grass being an index to the 

 influence of the white threads, or Fungus " spawn." 

 That influence is interesting. One might think that 

 the use the Fungus makes of the rotting vegetable 

 matter in the soil would tend to impoverishment, but 

 green plants do not use the organic materials in the 

 soil directly, nor until they have been changed into 

 salts like saltpetre. The spreading threads make some 

 of the organic materials in the soil more available, 

 and when they die away in the soil which they have 

 exhausted and push on into fresh soil, their decayed 



