Parasola plicatilis (Coprinus plicatilis)  (2 Photos and Description)

This is one of the smallest inky caps. Appears in grass after rain and collapses or disappears within a few hours. There are numerous lookalikes. Grooved cap. Free white gills that become black. Smooth hollow white stem. No partial veil.

Parasola plicatilis (Coprinus plicatilis)