Thallus saxicolous, crustose, unapparent to thin and scruffy, pale grey to olive brown, normally limited to a poorly developed hypothallus along cracks in the substrate surface or surrounding the scattered ascocarps. Apothecia sessile, lecideine, scattered to clustered and contorted, often in lines in the cracks in the rock surface, (0.2)0.3-0.5(1) mm in diam., usually rounded or broadly elliptic and slit-like; disc black to reddish black, flat to slightly concave, usually umbonate to gyrose; exciple strongly crenulated to plicated, brown to black, carbonated, with rare presence of photobionts in the base, 30-60(75) μm thick; hymenium hyaline, 89-124.5(139) μm tall, with sterile inclusions, K/I + blue; epithecium blackened with reddish areas; paraphyses not capitated, slender, 1.0-1.8(2.0) μm width. Asci narrow, clavated, (50)70-95(150) x 19-33(46) μm, walls K/I-. Ascospores hyaline, bacilliform to narrowly ellipsoid, small, more than 100 per ascus, (2.7-)3-5(-5.3) x 1-1.5 μm. Picnidia and conidia not seen.

CHEMISTRY. No TLC compounds found.

HABITAT. In Chile, Polysporina simplex is a poorly known species only known from this collection. It was found in La Campana National Park, in an area dominated by Jubaea chilensis in the northern part of the park. The species is well known from temperate to cold areas in the Northern Hemisphere, while also known in the Argentinean Patagonia (Magnusson 1936 – as Sarcogyne simplex, Calvelo & Liberatore 2002), Western Australia (Kantvilas 1998, McCarthy 2003), New Zealand (Galloway 1985) and the Venezuelan Andes (Hertel 1971 – as S. simplex).

NOTES. Polysporina simplex is the most common and widespread species of the genus. It is reported to occur in the Northern Hemisphere on a wide variety of substrata as calcareous to acidic rocks and man-made structures, such as gravestones and slate roofs, in dry to xeric habitats, although it is typically found on siliceous rocks. The species has been possibly overlooked in the continental Chilean territory given its small size and the inconspicuous crustose thallus. It is characterized by the sessile apothecia, the tall hymenia, the contorted to gyrose discs with plicate margins, being quite distinguishable from any other species known in the Chilean territory. Further comments and differences with members of the genus are provided by Magnusson (1935), Galloway (1985) and Kantvilas (1998).