“Bacidia” beckhausii group
Crustose lichens containing a trebouxioid alga; thallus thin, smooth, verruculose or immersed; apothecia with a non-algal rim that is like the disc in colour and texture, the rim formed of tightly packed hyphae embedded in gel, arrayed somewhat fan-like as seen in cross section, the disc often with a light dusting of pruina; hymenium formed of more or less straight, unbranched paraphyses embedded in gel, upper portions with a greenish-gray pigment that reacts K+ mauve; hypothecium colourless; asci like Micarea-type, having a thick, IKI+ blue tholus penetrated through its entire height by a pale axial mass surrounded by a darker blue tube (appearing as a pair of parallel lines that converge slightly near the tip); spores 8 per ascus, bacilliform, fusiform, or more or less acicular, colourless, with 1-3 (‑7) transverse septae.
Note: This species group is superficially similar to certain Micarea species, but differs in the presence of pruina and a well developed rim. In Micarea the exciple is often formed of gnarled, narrow, branched hyphae, versus broader, elliptical cells in the B. beckhausii group.
References: Ekman 1996; Ekman 2004a.
Bacidia beckhausii Körb.
Thallus thin, smooth, verruculose, or immersed; apothecia 0.15-0.35 mm wide, black, the disc covered in a thin layer of greyish pruina, the rim thin and receding with maturity, the outer layer of cells of the rim greenish grey or dark green, K+ mauve, C+ mauve, N+ red; hymenium 35-45 µ high, greenish grey or olive-green in upper portions, K+ mauve, C+ mauve, N+ red; spores with 3 (‑7) septae, bacilliform, straight, 15-25 × 2-2.7 µ.
Reactions: All spot tests negative.
Contents: No known lichen substances.
Habitat: On broadleaf trees and shrubs, especially on decaying bark or on Populus branches. Lower to middle elevations.
Similar Species: Micarea globulosella is similar in apothecial pigmentation and spore dimensions, but has a poorly developed rim and lacks pruina.
Specimens: Björk 13669, 17852.
Local Status: Occasional.