Approximately 64 species are classified in this family, divided among eight genera, including Geastrum, Myriostoma and Sphaerobolus. Sphaerobolus species are known as "shotgun fungus" or "cannonball fungus". They colonize wood-based mulches and may throw black, sticky, spore-containing globs onto nearby surfaces.[6][7]
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. The exoperidial rays are there to protect the endoperidial body and orchestrate spore dispersal.[8] 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.
References
^Corda ACJ. (1842). Icones fungorum hucusque cognitorum (in Latin). Vol. 5. Prague: J.G. Calve. pp. 1–92 (see p. 25).
^Hosaka K, Bates ST, Beever RE, Castellano MA, Colgan W 3rd, Domínguez LS, Nouhra ER, Geml J, Giachini AJ, Kenney SR, Simpson NB, Spatafora JW, Trappe JM (2006). "Molecular phylogenetics of the gomphoid-phalloid fungi with an establishment of the new subclass Phallomycetidae and two new orders". Mycologia. 98 (6): 949–959. doi:10.3852/mycologia.98.6.949. PMID17486971. S2CID196585804.
^Kirk PM, Cannon PF, David JC, Stalpers JA (2001). Ainsworth & Bisby's Dictionary of the Fungi (9th ed.). CABI Bioscience. p. 205. ISBN978-0-85199-377-5.
^Kirk, PM; Cannon, PF; Minter, DW; Stalpers, JA (2008). Dictionary of the Fungi (10th ed.). CAB International. p. 274. ISBN9780851998268.
^Lehman R (1985). "Black spots on houses—an insect or disease problem?". Penn Dept Agric Bur Pl Ind, Reg Hort. 11: 15–16.
^Kuhar, F., Castiglia, V., & Papinutti, L. (2013). Geastrum species of the La Rioja province, Argentina. Mycotaxon, 122, 145-156. https://doi.org/10.5248/122.145