Leptogium hildenbrandii (Garov.) Nyl.
Thallus foliose, rosette-forming, 5-10 cm diam., lobes more or less imbricate, apices round, thick and flexible, consistence gelatinous when moist, firm and rigid when dry, upper surface minutely and irregularly wrinkled and striate, brown-blackish, lead-grey tinged blue when dry and brown-greenish when moist, lower surface whitish, tomentose with rhizine tufts. Apothecia usually numerous, laminale, sometimes arranged in a line (like the suckers on an octopus tentacle), immersed in the thallus and a little oval at first, then prominent, 2-3 mm in diameter, disc brown-red, margin brown-greyish. Utriform asci of 80-90 x 20-35 µm according to our measurements. Hyaline spores, largely elliptical, 3-septate before maturation then muriform with 6-8 cells, 16-24 x 8-10 µm according to the literature, 20-26 x 8-10 µm according to our measurements. Photobiont: Nostoc. Chemical spot tests negative. On trunks of deciduous trees. Extremely rare in our prospection area. This rare thermophilic species from the South of France was once recorded in Brittany a long time ago but does not seem to have been found since.