Eccentric, said of a stem when it is attached to some other point than the center of the pileus.
Fimbriate, in the form of a delicate fringe.
Fistulose, becoming hollow.
Floccose, term applied to indicate delicate and soft threads, cottony extensions from the surface of any part of the mushroom.
Flocculose, minutely floccose.
Fugacious, disappearing.
Fuliginous (or fuligineous), dark brown, sooty or smoky.
Fulvous, tawny, reddish yellow.
Fusiform, spindle-shaped.
Fusoid, like a spindle.