Mycena haematopus

Scientific name:  Mycena haematopus (Fries) Quelet
Derivation of name:  Haemat- means "blood or "blood red"
and refers to the exuded blood-red latex where cut.
Synonyms:  
Common name(s):  Bleeding mycena.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Tricholomataceae
Occurrence on wood substrate:  Saprobic; solitary to
typically in clusters on well-decayed wood; June through
September.  
Dimensions:  Caps 1-5 cm wide; stipes 2.5-10 cm long and
1-3 mm thick.   
Cap:  Dry; reddish-brown at center to reddish-gray near
margin.      
Gills: Attached; whitish, staining reddish-brown; edges
minutely cottony-white.
Spore print: White.
Stipe: Brownish to reddish-brown.
Veil: Absent.
Edibility: Edible.
Comments:  Both cap and stalk exude a red latex where cut.
The occurrence of this latex together with the wood substrate
make this one of the more easily identifyable species of
Mycena.

More information at MushroomExpert.com: 
    

Figure 1. A striking cluster of bleeding mycena on wood.
Photo © Pam Kaminski.

Figure 2. Note the paler, striate margin.
Photo © Pam Kaminski.

Figure 3. The uneven color and darker stained areas on the
caps is part of the color variation for this species.
Photo © William Roody.

Figure 4. The color of the caps fades with age although
isolated darker blotches are often present even on older
specimens. Photo © Gary Emberger.

Figure 5. The gills of Mycena haematopus are attached and
the gill edges are whitish. Photo © Gary Emberger.

Figure 6. The dark red juice from the cut stipes applied to a
piece of paper illustrates why this species is called the
bleeding mycena. Photo © Gary Emberger.

Figure 7. You can almost see the blood-red latex inside
the caps. Photo © John Dawson.