Thallus: endolithic or chasomolithic, sometimes forming an ecorticate areolate crust, especially on fine clay or sandy soil Apothecia: black, carbonized, 0.2-0.5(-0.7) µm wide, c. 0.2 thick, scattered or contiguous, or in lines following cracks disc: reddish black, usually umbonate, becoming gyrose true exciple: parathecium: 25-50 µm thick, outer layer black, splitting, 15-25 µm thick, inner layer hyaline or yellow epihymenium: ±black with sometimes red hues, conglutinated, c. 20 µm thick hymenium: hyaline, 60-120 µm tall; paraphyses: 1-1.5(-2.4) wide, branching or not subhymenium: hyaline, 10-40 µm thick hypothecium: indistinct asci: narrowly clavate, (55-)65-100 x (12-)15-17(-20) µm, 100+-spored ascospores: hyaline, simple, 3-5 x 1.5-1.9 µm Pycnidia: similar in appearance to the apothecia, c. 0.3 mm. wide, black, convex; wall: 30-35 µm thick, black-brown, the inner part densely filled with chambers conidia: broadly ellipsoid, c. 1.7 x 1.5 µm Secondary metabolites: none detected. Substrate and ecology: on acidic or carbonaceous rocks, in sunny, open sites World distribution: Europe and North America Sonoran distribution: Arizona and southern California. Notes: Polysporina simplex is the most common species of the genus in North America. Only larger apothecia of P. urceolata with an umbo and splitting margin can be confused with P. simplex, which usually has smaller spores.