Chiodecton leprarioides

Chiodecton leprarioides forms a dull, pale-ochre crust on bark, between about 0.2 and 0.8 mm thick. The surface soon becomes almost completely dusted with farinose soredia—powder-fine bundles of fungal and algal cells that act as ready-made propagules—so the underlying thallus is often hidden. These soredia range from pale ochre to light brown and may darken in patches, giving the crust a speckled appearance. Around the margin the lichen produces a conspicuous chocolate-brown fringe of loose hyphae up to 2 mm wide (the prothallus). The photosynthetic partner is a filamentous green alga of the genus Trentepohlia, which lends an orange tint to freshly exposed tissue.^[2]

Reproductive bodies (ascomata) develop within pale to mid-brown stromata—small cushion-like mats of fungal tissue that sit on the thallus and measure 1–4 mm across. Each stroma contains dozens of minute, almost spherical ascomata sunk beneath the surface; in the field these are revealed only by pinpoint black pores (ostioles) arranged in irregular lines. Internally, the spore-bearing layer (hymenium) is about 100 μm high and turns deep blue in iodine (IKI ⁺), a reaction that helps confirm the species. The asci release eight colourless ascospores that are slightly curved, five-septate and 48–52 × 3.5–4.5 μm. No asexual pycnidia have been observed. Spot tests are negative and thin-layer chromatography detects no secondary metabolites, indicating that the lichen lacks the typical lichen products found in many relatives.^[2]