Buellia griseovirens

The thallus of Buellia griseovirens varies from immersed to thick, often pale grey with a black prothallus. They may be continuous or lacking, sometimes minutely cracked. It features scattered, crowded, or confluent grey-green soralia. Soralia are numerous, seldom confluent, often forming a mosaic up to 2 mm in diameter. The soredia, characterized by their powdery texture, are minute, measuring less than 0.01 mm in diameter. When newly collected, they exhibit a greenish-grey coloration, which fades to a pale yellowish-grey hue as they age in storage. These soredia are typically enclosed within circular, flat, or slightly convex soralia. Apothecia are very rare. The spores are irregularly 3-septate to sub-muriform. Initially, the apothecia are attached directly to the substrate (sessile) and appear flat with a distinct raised margin. As they mature, they become convex and lose their margin, blending seamlessly with the surrounding surface. The epithecium is dark brown. The hymenium is colorless and measures 110-120 μm tall. The hypothecium is dark brown. Asci are clavate, measuring 110 × 15 μm. Ascospores are pseudomuriform, ellipsoid, and measure (13-)15-28 × 7-13 μm.

Buellia griseovirens is distributed in Europe, Mediterranean Africa, the Middle East, and North America, including montane areas of southern California (Riverside and Los Angeles Counties). In Canada, it is found in Alberta, British Columbia, Nova Scotia, Ontario, and the Yukon Territory. In the United States, it occurs in Montana and Wyoming. It is also found in New Zealand.