This mushroom popped up in a penstemon I bought at the Fullerton College plant sale a few weeks ago, and was planting yesterday. The spore print is a little smeared -- the cap dried up and shrank to much less than a quarter of its original size during the time I was taking the print (overnight) -- but is clearly black in color.
Perhaps Coprinopsis friesii or one of the Parasola plicatilis group?
