Inoderma sorediatum

The crustose thallus of Inoderma sorediatum is about 1–2 cm (0.4–0.8 in) in diameter and up to 1 mm thick. Fresh individuals are pinkish, but specimens become white or yellowish after storage in a herbarium. The crust is made of soredia, which individually measure 20–35 μm in diameter. The photobiont partner of the lichen is trentepohlioid (i.e., filamentous, multicellular green algae from genus Trentepohlia). The algal cells contain an orange pigment that refracts in polarized light. The algal cells are spherical and measure 10––21 μm in diameter; they occur either singly or in short chains of 2–6 individuals, with adjacent cells becoming more ellipsoidal or rectangular in shape. Inoderma sorediatum is a sterile lichen, meaning it does not produce ascomata, nor ascospores. In rare instances, it has been recorded with pycnidia, which measure 170–280 μm and have a dark brown wall. The conidia are bacilliform in shape, and measure 3.5–5.0 by 1.1–1.3 μm.^[2]

The species contains confluentic acid and 2'-O-methylperlatolic acid, which are lichen products that can be detected using thin-layer chromatography. Inoderma sorediatum is the only member of genus Inoderma to contain both of these substances.^[2]

Inoderma sorediatum grows in the deep bark crevices of large trees (both living and dead), usually Quercus robur, but also Fraxinus excelsior. Other lichen species growing in close association include Chaenotheca chrysocephala, Chaenothecopsis cf. savonica, Chrysothrix candelaris, Lepraria spp., Opegrapha vermicellifera, and Reichlingia leopoldii. Inoderma sorediatum is only known to occur at the type locality.^[2]