These are the radiating gills of the toadstool known as weeping widow Lacrymaria velutina. For more about this toadstool, visit http://cabinetofcuriosities-greenfingers.blogspot.com/2009/10/weeping-widow.html
The surface layer of the gills, known as the hymenium, produces thousands of spores, and for these to be successfully released into the airstream the gills must always be vertically aligned, so they are very sensitive to the force of gravity and quickly realign themselves if the stipe of the toadstool bends away from the vertical and tilts the cap.
Here, at a microscope magnification of x40 you can see the spores lining the surface of the gills....
...and here, at a magnification of x100 you can see that each is shaped like a small brownish-black lemon..