Sarcosagium campestre

The thallus of Sarcosagium campestre is a thin, often inconspicuous crust, which ranges in colour from greenish or green-grey to blackish-brown. It may be more or less gelatinous when moist and can be reduced to scattered granules or an indeterminate dark crust in the field. In the protologue of S. biatorellum, the thallus was described as a very thin, spreading crust that became greenish-brown and semitranslucent when wet. The photobiont is chlorococcoid. The apothecia are 0.1–0.3 (sometimes up to 0.5) mm in diameter, sessile, barrel-shaped to convex, and dark red-brown, becoming translucent when wet. The disc is flat or slightly concave and opens with age to become cup-like, while the exciple is well developed, the same colour as the disc, and often thinly grey-pruinose. Massalongo described the young apothecia as punctiform (point-like) and flesh-coloured before they opened more fully and the disc became evident. The hymenium is 120–170 micrometres (μm) tall, and both the epithecium and hypothecium are colourless or pale yellow. The paraphyses are unbranched or sparingly branched, lax in K, with swollen apices. The asci (spore-bearing cells) are cylindrical and thin-walled. They lack an apical dome and turn blue when treated with iodine (K/I+). …

Sarcosagium campestre is an ephemeral pioneer, colonizing temporary or disturbed habitats where there is little competition from other species. Typical substrates include base-rich or acidic soils, decaying mosses, walls, paths, quarry floors, urban wasteland, and mine spoil heaps. In Eastern and East-Central Europe it has been described as a characteristic lichen of neglected habitats such as roadside scarps, edges of dirt roads, and sand-, gravel-, and loam-pits, where its apparent rarity may partly reflect under-recording. It has also been recorded growing on decaying lichen thalli, including Peltigera didactyla and species of Collema, as well as on rotting wood and other detritus. The species is frequently associated with metalliferous habitats rich in heavy metals. In southern Poland, it has been recorded from abandoned zinc-lead mining areas on the Silesian-Kraków Upland, growing on soil and bryophytes on zinc- and lead-enriched substrates. In Maine, United States, it was collected from the fine-textured, metal-enriched, waterlogged soils of the tailings pond at the Callahan Mine, a copper- and zinc-enriched Superfund site, where it was treated as one of the indicator species for sites important for metal-tolerant lichens. …