OCCURRENCE OE " FAIRY-RINGS." 23 



succeeds. This being cut or eaten off, the soil may sooner or 

 later become even more exhausted than before ; and it is accord- 

 ingly frequently observed that the grass within is less luxuriant 

 than that outside the ring. Initiative experiments, upon which, 

 however, we would not place implicit reliance, have, indeed, shown 

 a lower percentage of nitrogen in the surface soil within the 

 circle than at an equal depth either under or without the circle. 

 Leguminous plants are not excluded from the area within the ring ; 

 but whilst Lathyrus pratensis and Trifolium pratense, plants 

 which on the land in question have shown themselves very depen- 

 dent on artificial supplies of potass, seem to T be discouraged, 

 Lotus corniculatus and Trifolium repens, species which maintain 

 their position under marked conditions of exhaustion of soil, are 

 fairly abundant. At any rate, it would appear that, in the case 

 of "rings," the soil underneath the fungus-growth has become 

 unfitted to support another crop, or successive crops, of fungi. 

 Accordingly, supposing the soil of the plot to be favourable, the 

 ring develops always outwards — that is, on what is to the fungi 

 virgin soil ; and hence the annual enlargement. 



It will be seen that in these facts we have an interesting illus- 

 tration of what may be called natural rotation. The original 

 fungi probably receive their nutriment from extraneous sources ; 

 but once established, they must, for the extension into " rings," 

 depend upon other supplies, which, if due to the soil itself, are ob- 

 viously unfavourable, either in condition or in distribution, to 

 the surrounding vegetation, and especially to the grasses, w T hich 

 do not flourish until the matter taken up by the fungi becomes 

 available to them as manure, when at once they show very great 

 luxuriance. Or is it, as already suggested, that the mycelium 

 develops, so far as its nitrogen is concerned, not at the expense 

 of that which may be said to have become a constituent of the 

 soil itself, but of that accumulated in the vegetable debris from 

 former growth within the soil, or even parasitically — that is, at the 

 expense of the nitrogenous matters of the roots of not dead but 

 very sluggish vegetation ? 



These points are obviously of very considerable interest from 

 both a chemical and a physiological point of view ; and it is much 

 to be hoped that botanists and vegetable physiologists who may 

 have special knowledge on the subject will bring it to bear on the 

 questions which seem to be at issue — or that, in so far as such 

 knowledge is not yet available, some may be induced to take up 



