The most complete and symmetrical grass rings are formed by Marasmius oreades, the fairy ring champignon, but the mushroom and many other species occasionally form rings, both on grass-lands and in woods.
The mushroom is a semi-deliquescent fungus which rapidly falls into putridity in decay, whilst the champignon dries up into a leathery substance in the sun, but speedily revives and takes its original form again after the first shower.