Other common names: Common Earthstar, Sessile Earthstar, Rounded Earthstar
The earthstar is a common puffball-type mushroom, but is often overlooked because it is small (3/4" or so) and is usually found in thick leaf litter. The two earthstars in the photo above are both immature. The sporocarp on the one in the foreground is about half open, but hasn't even started opening yet on the mushroom in the rear.
When fully open, the rays recurve back underneath the spore sac. In this case, they are mostly hidden in the leaf litter and appear to have damaged areas.
When fully dry, spores are ejected through the apical pore. Rain striking the spore sac or wind blowing across the apical pore aid disbursal.
This group of earthstars was really pushing the limits of their growing season. I took the first two photos on Saturday. That night our temperature dropped into the mid-twenties. I think the less developed earthstars were killed by the freezing temperatures. However, the muchrooms that were farther along appear to have already developed their spores. It was time for them to dry out and disburse the spores anyway. The bottom photo was taken on Tuesday.
Thanks to Mushroom Observer for the ID and to Mykoweb and Mushroom Expert for additional information.
