Buellia oidalea

The thallus of Buellia oidalea is crustose, varying from thin and rimose-areolate to thick and rugose-verrucose or even subsquamulose. The prothallus is often present, appearing black. The thallus surface is yellowish white to glaucous gray, smooth, and esorediate. The medulla is white and lacks calcium oxalate. The apothecia of B. oidalea are lecideine and commonly found, ranging from 0.2 to 2 mm in diameter, and are sessile in nature. Initially, the disc is black, devoid of pruina, and flat, but as it matures, it becomes convex. The margin starts as distinct but eventually becomes excluded and black. The proper exciple measures between 35 and 95 μm in thickness, lacking secondary metabolites, and appears uniformly dark brown throughout, with carbonized cells smaller than 6 μm. It is transient and accompanied by a brown hypothecium, which is less than 280 μm thick. The epihymenium shares a continuous brown pigmentation with the outer exciple. The hymenium is hyaline, generously interspersed with oil droplets, and measures 115 to 165 μm in height. The tips of the paraphyses typically measure less than 3 μm in width and are adorned with distinct apical caps. Asci are clavate, of Bacidia-type, measuring 95 to 112 x 20 to 40 μm, and typically contain 8 spores. The ascospores of B. …

Buellia oidalea thrives on the bark and wood surfaces of trunks, branches, and twigs found on both broad-leaved and coniferous trees and shrubs. Its habitat encompasses various open environments along the Pacific coast, including dune areas, salt marshes, chaparral, and coastal deserts. This species is predominantly found along the Pacific coast and islands of North America, spanning from Coos County, Oregon to Baja California Sur. Notably, within the Sonoran region, it has been documented in the coastal fog zones of southern California, Baja California, and Baja California Sur.