Geastraceae

The Geastraceae is a family of basidiomycetes fungi which includes the “earthstars”. Approximately 64 species are classified in this family, divided among eight genera, including Geastrum, Myriostoma and Sphaerobolus. They colonize wood-based mulches and may throw black, sticky, spore-containing globs onto nearby surfaces. The fruiting 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 like a tumbleweed. Once mature, their exoperidium splits into a variable number of rays, which give Geastrum their visible star shape. In wetter weather, the “petals” moisten and uncurl; some even curl backward lifting the spore sac up. This allows rain or animals to hit the spore sac, emitting spores when enough moisture is present for them to germinate and establish. Read more on Wikipedia.