Marasmiellus nigripes

This is a key to gilled mushrooms, that is, mushrooms having a definite cap with a fertile surface consisting of gills. The fruiting body usually also has a stem, although that may be lateral or absent (usually, then, the mushroom is growing from wood). You can use this key to identify mushrooms that you find.

Fruiting body containing fibers (usually in the stalk)

Spore print "light-colored": white or buff, sometimes tinged with pink or tan. Greenish and (except for the Russulales) yellow spore prints also go here
Stalk fibrous, not fracturing like a piece of chalk

None of the special features distinguishing the other white-spored genera:
Gills not free, as in the Lepiotas and Amanitas
Basidia not extra-long, as in the Hygrophoraceae
Spores smooth, except for Lentinellus

Growing on trees or dead wood, leaves, or sticks, or organic debris, often in moss

Shaped like a “normal mushroom”
Small and fragile to medium-sized, except for one large, grey-capped species

Fruiting body small: cap up to 1 1/4" across (and most clearly smaller than that)

Marasmiellus     Genus Cap usually white; convex becoming flat, plicate in maturity; often thin to the point of being translucent Gills usually very, very distant ("few and far between" says Arora (1986) ), often forking or with cross-veins Stem thin but not wiry; often much darker than cap, at least towards the base in maturity Often with wiry rhizomorphs

Links from Look-alikes Micromphale     Genus Fruiting body arising from black rhizomorphs Usually revenant Odor foul Stalk hairy or scurfy

Marasmiellus nigripes     (Schweinitz) Singer