Usnea subfloridana Stirt.
The most commonly recorded Usnea species in the islands. Commonly found on trees and fence posts. The thallus is very variable in the degree of branching. The combination of a dense medulla, lack of articulation, blackened base, nature of the soralia and chemistry are diagnosic
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
Thell & Moberg, editors (2011) Nordic Lichen Flora, Volume 4: Parmeliaceae