Sphaerophorus fragilis (L.) Pers.
A more compact, bushier species than the similar Sphaerophorus globosus, with more even branching. On granite, often at higher altitudes
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Irelandd
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species