A saprobe on decaying parts of broadleaved trees, often found in clusters. Rather similar to Bisporella citrina, but that species is sessile, while this one has a short but obvious stem. Infrequently recorded and mostly from the south of Britain

References: 
Breitenbach & Kranzlin (1984) Fungi of Switzerland, Volume 1, Ascomycetes
Hansen & Knudsen (2000) Nordic Macromycetes, Vol.1: Ascomycetes