Clitocybe clavipes

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 the ground

Found in woods
Not rooting

Gills attached to decurrent
Coloration usually white to greyish brown, sometimes purple or with purple tones
Never with a ring of any kind

Gills attached to decurrent, crowded
Cap glabrous, small to very large; often aging into a funnel shape
Spore print often tinged with pink or buff
Look for things here if they have non-free gills and don't fit the other taxa

Stalk widening drastically towards the bottom, often until it is as wide as the cap
Cap conical when young, flat with a very broad umbo in maturity
Gills strongly decurrent, often slanting diagonally from the margin to the stalk
Thus, the point where the gills meet the stalk is usually the thinnest part of the mushroom, and young mushrooms have sort of an hourglass-shaped profile

Clitocybe clavipes     (Fries) Kummer