Nov. 17, 1887] 



NA TURE 



6.3 



The chief additional facts may be summarized as 

 follows : — The fungi remove large quantities of carbon, 

 nitrogen, and especially phosphoric acid and potash, from 

 the soil. The soil inside the ring contains less nitrogen than 

 that under the ring, and this again less than the soil outside 

 the ring ; a gradual exhaustion of nitrogen, then, is taking 

 place as the fungus and rank grass extend the ring centri- 

 fugally, and this is promoted by the removal of the grass. 



These observers also demonstrated the spread of the 

 mycelium : it is in greatest abundance just below the 

 outer edge of the ring. They conclude that the fungus 

 has powers of obtaining nitrogen from compounds in the 

 soil which are not available to the roots of the green 

 herbage, but after the decay of the fungus mycelium the 

 grasses can avail themselves of part of the nitrogen. The 

 grasses — being plants containing chlorophyll — of course 

 obtain their carbon from the carbon dioxide of the atmo- 

 sphere ; but the fungus — equally of course, in the light 

 of physiology — obtains its carbon from some organic sub- 

 stances in the soil. The accumulation of phosphoric acid 

 and potash has already been accounted for. 



We may now sum up, then, the rational explanation 

 of these curious fairy-rings as follows. 



A mushroom spore may be supposed to start its growth 

 in or beneath the dung of cattle, or a bird, on poor soil ; 

 the first crop of mushrooms, produced from the myce- 

 lium to which the spore gave rise, exhausts the soil of 

 available carbon, nitrogen, phosphorus, potash, and other 

 substances, storing all it can get in its own substance. 

 The mycelium extends centrifugally "into fresh fields and 

 pastures new," and the next crop of mushrooms arises 

 :it a distance from the centre ; and so the growth pro- 

 ceeds. The grasses, among the roots of which this 

 extension is going on, now avail themselves of the 

 rich manure afforded by the decomposition of the older 

 mycelium, and a struggle for existence is set up which 

 results in the victory of the coarsest and rankest-growing 

 species. These in their turn exhaust the available supply, 

 and if cut it is removed in their substance : no wonder, 

 then, that the inner parts of the area are poor, and 

 support little or no herbage. 



Messrs. Lawes and Gilbert's researches also showed 

 that if the growth of the herbage is promoted by means 

 of manures containing much available nitrogen the fungi 

 are found to suffer, and the " fairy- ring " may be brought 

 to an end. Again, unfavourable seasons of drought may 

 cause the death of the mycelium, and rings which have 

 flourished for years be thus destroyed. 



We have attempted in this article to give a complete 

 explanation of the rise and progress of "fairy- rings," as 

 afforded by modern science. That much is clear which 

 was previously obscure will have to be conceded ; but are 

 all the facts covered by the explanation.? There are 

 some inquiring spirits who are never satisfied with an 

 explanation, and we run the risk of being classed among 

 these malcontents, but there are one or two curious little 

 points which still obtrude themselves upon our attention. 



There is, in the first place, some difficulty in realizing 

 how the fungi manage to obtain their large supphes of 

 carbon and nitrogen and other elements from poor 

 shallow soil, in the absence of larger quantities of organic 

 matter than may occur : there is, in fact, considerable 

 difficulty about the whole question of the nutrition of the 

 fungus. A second point is that we find the ultimate fila- 

 ments into which the mycelium of the fungus breaks up 

 becoming lost among the roots of the grasses ; and if the 

 latter are carefully washed and examined with the micro- 

 scope, their fibrils and root-hairs can be seen to be 

 infolded by delicate hyphas, and in some cases the root- 

 hairs are pierced by them. We do not know that this 

 has been demonstrated before, but we find it the rule 

 with Marasmius, and have already succeeded in detect- 

 ing something of the kind in other forms. 



Now this looks very like parasitism.; and we are 



tempted to pause before accepting the last explanatioa of 

 fairy-rings as conclusive, or covering all the facts. It 

 may be, in fact, that the hyphae of the fungus stimulate 

 the roots of the grasses to increased activity : this would 

 account for the rampant growth and the result of the 

 struggle for existence. Subsequently the hypha: kill the 

 grass-roots— or at any rate those of some species— which 

 accounts for the bare patches in some rings. It also 

 easily explains the sources of the carbon and nitrogen, if 

 the hyphae absorb nutritive materials from the hard- 

 working grass-roots. This being the case, fairy-rings 

 become still more interesting, since they afford an illus- 

 tration of symbiosis of a peculiar kind, at any rate 

 during part of the time that the grass and the fungus are 

 in contact ; and it seems not improbable that the theory 

 of the formation of fairy-rings will have to be modified 

 somewhat as follows. 



A fungus-spore starts its mycelium among the roots of 

 the grasses, and the hyphje obtain a hold on some root- 

 hairs and fibrils ; the mycelium thus parasitic on the 

 roots reacts in a stimulating manner on the latter, and we 

 have a symbiotic relationship established between the 

 fungus and the host. The consequence is that both 

 flourish, and become rampant. It may be that only some 

 grasses are thus stimulated, or even attacked, and this 

 will affect their struggle for existence, and result in the 

 selection of a few coarse forms. In time the hyphae or 

 the roots get the upper hand, and this is expressed in the 

 survival of the grass, or its decay ; in some cases it is 

 clear that hyphee are living at the expense of dead and 

 dying roots. 



However, until the results of investigations at present 

 going on are set forth more at length, it is impossible ta 

 say which of the above explanations is the true one ; in any 

 case, the attachment of fungus hyphte to the living grass- 

 roots needs explanation, and it must ako be allowed that 

 at present we have no satisfactory theory to account for 

 the nutrition of these rampant mycelia. But this is 

 not the place to do more than point out how interesting 

 the subject is, and how promising a field for further 

 research it offers. 



NOTES. 

 Mr, W. Bateson, Fellowof St. John's College, Cambridge, who 

 has just returned from a zoological expeuition to Central Asia, 

 and is well known for his researches on Balanoglossus, has 

 been awarded the Balfour Memorial Studentship in Animal 

 Morphology. 



The second meeting of the newly-formed Anatomical Society 

 of Great Britain and Ireland will be held on Tuesday, Novem- 

 ber 22, at University College, Gower Street, at 5 p.m. The 

 following papers will be read : — Prof. Sir William Turner, 

 F.R.S., (i) "Variations in the Hippocampus Major and 

 Eminentia Collateralis," by Robert Howden, and (2) "A 

 Metallic Body in the Spinal Canal," by David Hepburn ; 

 (3) " Minute Anatomy of Clarke's Column in Spinal Cord of 

 Man, the Monkey, and the Dog," by Dr. Mott ; (4) "The 

 Arteries at the Base of the Brain," by Prof. Bertram C. A. 

 Windle ; (5) " Note on the Functions of the Sinuses of Valsalva 

 and Auricular Appendices, with some Remarks on the Mech- 

 anism of the Heart and Pulse," by Mayo Collier. A number 

 of interesting exhibits are also announced. 



On Tuesday evening the second part of an important paper 

 upon the causes of accidents in mines and the development of 

 measures and applications for combating or avoiding them was 

 read by Sir Frederick Abel at the Institution of Civil Engineers. 

 The first part of the paper was read in May last, at the close of 

 the session. Sir Frederick's ideas will be discussed at the 

 meeting of the Institution next Tuesday. 



