We know as little of the origin of fairy-rings, as of any other phenomenon connected with the growth of funguses. These fairy-rings are of all sizes, from one and a half to thirty feet in diameter; the grass composing them is observed in spring, to be of a thicker growth than the surrounding herbage, and, in consequence of the manure afforded by the crop of last year, is of a darker colour. Within these rings are frequently seen certain varieties of this class of plants, very generally Agarics, though puff-balls frequently, and occasionally the Boletus subtomentosus, affect a similar mode of growth. Of the Agarics which appear in these circles, some of the principal are Agaricus oreades, Ag. prunulus, Ag. Orcella, Ag. Georgii, Ag. personatus, and Ag. campestris. As all these feed at the expense of the grass, (by exhausting the ground that would otherwise have furnished it with the necessary supplies,) the richest vegetation in the field is generally the first to become seared. These rings (giving birth to some one species which, dying, is not unfrequently succeeded by another a little later, and this perhaps by a third, in the same order of occurrence) continue to enlarge their boundaries for a long but indefinite period.

It seems not easy to determine precisely, to the operation of what cause or causes the increase in the size of these circles from year to year should be attributed. Is it the projectile force with which the spores are disseminated all round, that has carried them so uniformly beyond the margin of the last ring as to form a concentric circle for the next of larger diameter beyond? Or is the cause to be sought underground, in the general spread of the spawn of last year in all directions outwards, but only fertile in a concentric ring beyond the site of the last crop, which had already exhausted the ground, and so rendered it incapable of supporting any new vegetable life? Or do both these causes conspire in this result? The quantity of spawn and of the spores necessarily contained in it, and the depth to which they penetrate under the surface of the soil, renders the possibility of their spreading in the latter way easily conceivable.[102]