From M. J. Berkeley   13 July 1875

My dear Sir

I do not think that the subject of fairy rings has been fully carried out from the first formation. The theory is that the spawn radiates, that the spawn near the centre is exhausted, while that which has spread out is fertile, & that the rank verdure of the grass depends upon the decay of the fungi supplying nitrogenous manure. If from any circumstance a portion of the first emitted spawn dies only an arc of a circle is formed. The difficulty is to trace the early commencement of the ring which I do not recollect that any one has done. There is no doubt that the diameter of the ring increases year after year. As much as 15 yards in diameter have been observed.¹

D^r Gilbert has lately read an important paper before the Linnean Society which will shortly be published shewing that rings are for the most part formed in upland pastures poor in nitrogenous matter, & connecting this with the fact that clover does not get the greater part of its nitrogen from the soil, while the fallen leaves supply the soil with nitrogen & so prepare it for wheat.²

Many woodland fungi form large rings amongst the fallen leaves, which are however only to be seen when the fungi themselves appear. Agaricus nebularis, Hydnum repandum are examples.³

I am, my dear Sir, | very sincerely yours | M J Berkeley.—