Wikipedia
The Geastrales are an order of gasterocarpic basidiomycetes ( fungi) that relates to Cantharellales. The order contains the single family Geastraceae, commonly known as "earthstars", which older classifications had placed in Lycoperdales, or Phallales.
About 64 species are classified in this family, divided among eight genera, including the Geastrum, Myriostoma and Sphaerobolus. The Sphaerobolus are known as "shotgun fungus" or "cannonball fungus". They colonize wood-based mulches and may throw black, sticky, spore-containing globs onto nearby surfaces.
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 it will puff out spores when enough moisture is present for them to germinate.