Genus SclerodermaGENUS SCLERODERMA
The species of the genus Scleroderma, or thick-skinned puffballs, represent a transition from the subterranean forms to those which emerge from the ground and have a definite opening from which they eject their spores. To illustrate: there is one group (Hymenogastrales) in which the species remain in the ground, even when mature, unless washed out by rains or nosed out by animals, and which rely upon being crushed by accident or upon the disintegration of their rinds to free their spores.
All true puffballs push themselves out of the ground before the spores are mature, and then, by rupturing the skin in a definite manner when mature, disperse their spores. The thick-skinned allhall goes a step farther than the first mentioned and emerges from the ground; but it remains behind the true puffballs, which disperse their spores from a definite opening, for it ruptures the skin irregularly.