Earthstar

The earthstars are the family Geastraceae of gasterocarpic basidiomycetes (mushrooms). It includes the genera Geastrum and Myriostoma. About sixty-four species are classified in this family, divided among eight genera.

The fruit bodies of several earthstars are hygroscopic: in dry weather the "petals" will dry and curl up around the soft spore sac, protecting it. In this state, often the whole fungus becomes detached from the ground and may roll around as a tumbleweed does. When the weather dampens the "petals" moisten and uncurl and some even curl backward lifting the spore sac up. This then allows rain or animal movement to hit the spore sac so that it will puff out spores when there is enough moisture for them to germinate.