Myriospora rhagadiza (Nyl.) K. Knudsen & L. Arcadia

     Thallus formed of 0.5-1.5 x 0.2-1 mm squamules, scattered or close, sometimes in rosettes, surface smooth, dull, ochraceous-brown, olive-brown if moist, chestnut, sometimes blackish-brown in a sunny situation but most often leather or horn color, sometimes with orange tinges on iron-rich substrates, paler margin for the peripheral scales, blackish for the central scales. A section of the thallus shows that the algal layer is not continuous but interrupted in places by bundles of hyphae forming like "pillars". Apothecia immersed in the thallus, 1-4 per squamule, rounded to oval, 0.2-0.6 mm in diameter, disc concave, red-brown, prominent margin concolor to thallus or darker. Tiny spores, several hundred per ascus, colorless, 3-4 x 1.5-2 µm according to the literature, 4-5 x 1-2 µm according to our measurements. Paraphyses narrower towards the base than towards the top. Photobiont: green algae. C-, K + red, KC + red, P + yellow. Species of siliceous coastal rocks that are not very homogeneous and not too acidic, subject to spray, for rocks subject to seawater projections see Myriospora rhagadiza forma. N.B. This taxon is very variable because it is very sensitive to its substrate, it belongs to the group of Myriospora (Acarospora) smaragdula with a very confused and very confused taxonomy and whose taxa are variously interpreted by the authors ...