Usnea is a genus of lichens that are usually called beard lichens or old man’s beards because of their light grey hairy twigs hanging from tree branches as a grey beard. Usnea includes many species that are difficult to distinguish.
The thalli of Usnea have an elastic cord inside that is discovered when stretching one of its twigs between the fingers.
The species of the Usnea genus usually live on the low branches of trees, preferably in humid areas without atmospheric pollution. Usnea can be very abundant in old trees in subalpine forests.
The usnic acid that Usnea lichens contains has antiseptic properties.
The specimen in the images was photographed in L’Obac mountain range, on branches of Cistus albidus. The disc-shaped apothecia characteristic of Usnea florida are not here; this could be Usnea barbata, a common species. But the identification of Usnea species is not possible based just on photographs.
[photos Jordi Badia]