Marasmius cohaerans

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)

Basically, the members of this genus can look like members of any other SmallLignoTrich.
You might want to check here first if your mushroom is very small, has a thin, wiry stem or is revenant. Or if it looks like the picture. :-)
Else, check this genus if you can't find your mushroom anywhere else

Marasmius cohaerans     (Persoon: Fries) Cooke & Quélet