Phacidium

Phacidium is a genus of fungi belonging to the order Phacidiales. These fungi are typically characterized by their stroma, which are often dark, flattened, and disc-shaped structures where the fruiting bodies develop. The asci, which contain the spores, are typically clavate and arranged in a hymenium. The ascospores are usually hyaline and septate.

Members of the genus Phacidium are primarily saprobic, meaning they obtain nutrients from dead organic matter. They are often found on the leaves, stems, and bark of various plant species, playing a role in decomposition. Some species can also be weakly parasitic, causing minor damage to living plants, though they are not generally considered major plant pathogens.

The genus was first described by Elias Magnus Fries in 1815. The type species is Phacidium ulicis. Over time, various species have been described and assigned to Phacidium, though its taxonomy has undergone revisions. Identification of specific species often relies on morphological characteristics of the stroma, asci, and ascospores, as well as host plant association. Research continues to refine the understanding of the evolutionary relationships and ecological roles of Phacidium species.