Agrocybe acericola

Scientific name:  Agrocybe acericola (Peck) Singer
Derivation of name: Acer- refers to "maple", a
common substrate for this fungus. 
Synonyms:  
Common name(s):  Maple Agrocybe
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Bolbitiaceae
Occurrence on wood substrate:  Saprobic; solitary to
scattered on decaying deciduous logs and wood chips;
April through September.
Dimensions:  Caps are 3-10 cm wide; stalks are 5-10
cm long and 0.5-1 cm thick.   
Cap:  Ochre-yellow when young, fading to tan in age;
moist, smooth or wrinkled when fresh, becoming dry,
cracked and fissured with age.      
Gills: Attached; off-white when young, becoming
brown.
Spore print: Cinnamon to rust.
Stipe: Whitish at first, becoming brownish with age;
white rhizomorphs at the base.
Veil: White membranous ring at first, staining cinnamon
by the spores.
Edibility: Inedible.
Comments: May be quite common in urban areas on
hardwood chips used in landscaping.

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Figure 1. Maple Agrocybe. Note the membranous
partial veil. Photo © Steve Nelsen.    

Figure 2. Note the attached gills and the white rhizomorph
at the base of the stem of the inverted specimen.

Figure 3. A specimen collected at a foray. The partial veil is
collapsed about the stem and is the color of the spores
deposited on it.