Leccinum carpini  (Schulzer) Moser ex Reid (1965)
Syn: Leccinum griseum (Quelet) Singer nom. amb. 
According to Noordeloos the correct name is Leccinum pseudoscabrum, but here I'm using the more popular name, carpini

Collection: Bulgaria, Vitosha Mountain, Elevation: 1,200m, Fagus, Betula and Carpinus

This is a common species in  broadleaved forests in mid-elevations.

This species is easily distinguished microscopically due to the round cells on the epicutis.