While most of the earthstar fungus grows below ground in a symbiotic association with tree roots, the fruiting body makes its appearance in late fall. When it first comes up, the fruiting body looks like a giant sphere. But then in response to rain, the outer star-shaped covering opens up to reveal the central spherical spore sac. This acts to push aside debris and raise the sac up off the ground, providing the spores a chance to travel greater distances when they are released through the opening in the top of the sac.
I spotted a patch of earthstars at Arabia Mountain (east of Atlanta) this weekend. The one below is somewhat dried out, so it isn't fully open. The other earthstar shown below is from last year at Joyce Kilmer in North Carolina.
|At Arabia Mountain, November 2011.|
|At Joyce Kilmer Memorial Forest, November 2010.|