Porpidia macrocarpa  

Thallus variable, but usually immersed to thin and continuous to rimose, rarely thicker and becoming areolate, surface roughened-subarachnoid, pale grey to greenish grey, frequently patchily or continuously ‘oxidized’ orange to rust red. Medulla I–. Prothallus indistinct at margins of immersed thalli, but wavy, black and ± distinct at margins of superficial thalli. Isidia and soredia absent. Photobiont chlorococcoid.
Anamorph: no information available.
Teleomorph: ascomata apothecia, to 3 mm diam., ± sessile, abundant, scattered or crowded, constricted at the base. True exciple thick and tumid (150-200 µm wide), mostly persistent, black, shiny, raised, entire to flexuose; hyphae 3-9 mm diam. Disc subconcave to flat or convex, black or brown-black, matt or shiny, occasionally grey-pruinose, often ± gyrose or with larger apothecia appearing to divide by formation of secondary margins within the disc. Epithecium pale brown to olive-brown. Hymenium (70-) 80-100 (-120) μm tall, hyaline. Hypothecium and inner exciple sometimes with K+ reddish tinge (forma nigrocruenta). Interascal tissue of paraphyses, septate, branched-anastomosing, netted, slightly swollen at the apices. Asci clavate, 8-spored. Ascospores (13-) 16-20 (-26) × (5-) 6–11.5 μm, ellipsoidal to fusiform-ellipsoidal, aseptate, hyaline, thin- and smooth-walled, at least sometimes with a broad gelatinous sheath.
Chemistry: medulla K± yellowish, Pd± orange (± stictic and cryptostictic acids).