Annulus undersurface: single
images/Annulus_undersurface_single/Annulus_undersurface_-_single.jpg
This feature is best observed just after the annulus has broken from the pileus edge. In older fruit-bodies features of the underside of the annulus may collapse, and the annulus itself may collapse onto the stipe.

Choose this state if: the underside of the annulus is smooth, with no distinct scales or ridges.