Cladonia ciliata var. tenuis (Flörke) Ahti
C. ciliata var. tenuis, with is very variable. The podetia are greenish grey to yellowish (usnic acid). C. ciliata var. ciliata, without usnic acid, is less frequent than var. tenuis though their distributions and habitat requirements are similar.
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
Ahti, Stenroos & Moberg. Editors (2013) Nordic Lichen Flora. Volume 5 Cladoniaceae