Many other fungi in addition to the fairy-ring champignon grow in circles, so that this habit must merely be taken with its other characters in cases of doubt.
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.
Dryophilus has sometimes been gathered in mistake for the champignon, but this too grows in woods where the champignon never grows; it has a hollow instead of a solid stem, gills crowded together instead of far apart, and flesh very tender and brittle instead of tough.
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.
A small esculent ally of the champignon, named M.