Usnea subfloridana Stirton

    Thallus shrubby, 5-10 (or more) cm tall, lower part black, erect or pendulous according to local conditions, made of numerous cylindrical, thin branches with dense medulla, highly ramified, branching isotomic-dichotomous with minute transverse crackings or rings without interconnecting longitudinal cracks, but often densely warted, papillose, with  terminal small fibrils, 1-3 mm long, whip-shaped, tips often covered with numerous round or oblong soralia with spiny isidia, whole thallus more or less pale grey-yellow, pale green-greyish according to exposition and humidity. Usually infertile but apothecia occasional, at branch tips, round, flat, 0.2-0.8 mm diam., papyraceous, whitish to light brown, surrounded by scarce small cilia, voir Usnea subfloridana forme fertile. Photobiont: trebouxioid. C-, K+ yellow > golden yellow, KC-, Pd+ instantly orange or much seldom C-, K-, KC-, Pd-. Usnea fairly common in our prospecting area, on trunks and branches of trees whatever the level, very seldom on rocks, but see : Usnea subfloridana forme saxicole.

_ Not to be confused with Usnea wasmuthii  much rarer, with longitudinal cracks on the cortex towards the black base of main branches and with different chemical reactions.

N.B. Molecular biology investigations have shown that this species is similar to Usnea florida that is almost always fertile, with bigger and more ciliate apothecia, and with secondary branches without soredia and isidia.