Mycena pseudocorticola

A small bluish-grey or slate-grey bonnet found on the bark of deciduous trees.  The cap is hemispherical or broadly conical, with a pleated appearance.  The gills are few and adnate/decurrent.   It becomes brownish with age.

Other small Mycena species may be present on the boles of deciduous trees.  Older specimens are hard to distinguish from M meliigena, even microscopically, which occurs in in the same habitat. 

Globose spores, cheilocystidia with long branching projections ('medusa' form), short diverticulate stem cystidia

Photograph in its habitat; and also from top down, in side view and underneath to show gills; note habitat and substrate.  Note that only fresh specimens in good condition can be verified from photos.

Mossy bark of deciduous trees