Pinwheel (Marasmius rotula)
Marasmiaceae or Fairy Circle Family
 

Tiny mushroom, usually much less than an inch wide. Cap flat on top, with a sunken center, deeply ribbed, white. Stalk wiry thin, pale when young, but turning dark brown to black. Gills few and far apart (a condition called distant), whitish. Looks like a tiny white beach umbrella. Grows singly or in small groups on fallen twigs and woody debris.

A delightful little mushroom if you notice it, but most people don't. It occurs in Wildwood, but how common it may be is anybody's guess.

This is a fairly easy mushroom to identify, based on its very small size, white color, ribbed cap and wiry stem. Another white pinwheel is M. cappilaris, but that species has a rounded cap, rather than a flat-topped one. An even more definitive difference is that M rotula grows on twigs and woody debris, but M. cappilaris grows on fallen leaves and pieces of leaves. M. cappilaris has not been reported in Wildwood, but given its small size it could grow there by the hundreds. Orange pinwheel (M. siccus) is also similar, except for its brilliant orange color. White marasmius (Marasmiellus candidus), is somewhat similar, but larger, and has a fleshy two-toned stalk.