Armillaria tabescens

Scientific name:  Armillaria tabescens (Scop.:Fr.) Singer
Derivation of name:  Tabescens means "decomposing"
referring the activities of this mushroom.
Synonyms:  Clitocybe monadelpha Morgan; Clitocybe
tabescens Bres.
Common name(s):  Ringless honey mushroom.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Marasmiaceae
Occurrence on wood substrate:  Parasitic/saprophytic; in
cespitose clusters at the base of living or dead trees (often
oak), stumps, or from buried wood or roots; June through
fall.    
Dimensions:  Caps are 3-10 cm wide; stipes are 5-20 cm
long and 0.4-1.6 cm wide.   
Cap:  Dry, yellow-brown with darker hairs or tufts of fibers.
Gills: Subdecurrent; whitish, becoming pinkish-brown.  
Spore print: White.
Stipe: White above, darkening to brown near the base.
Veil: Absent.
Edibility: Choice with caution.
Comments: Sometimes occurs in dense cespitose clusters.
Of the Armillaria species, this is the most distinct due to the
lack of a ring.

More information at MushroomExpert.com: 


Figure 1. The ringless honey mushroom occurring in very
dense clusters is not unusual. Photo © John Plischke III.

Figure 2. This clump appeared in a grassy area and not at
the base of a tree or stump. It was attached to buried wood,
perhaps a dead root.

Figure 3. The appearance of another very dense cluster of
ringless honey mushroom, much lighter in color than those in
Figure 1. Photo © Larry Grand.

Figure 4. Sometimes when mushrooms are close together
they deposit spores on adjacent caps. The caps on the right
are whitish with spores and serve as a field spore print.
Photo © William Roody.

Figure 5. A closeup of some of the mushrooms in Figure 4.
showing the white deposit of spores.
Photo © William Roody.