Calicium abietinum

The lichen has a lichenized life habit. Its thallus is immersed.[2]

The apothecia are not pruinose, 0.6-0.9 mm tall, and 6-11 times as high as the width of the stalk. The stalk is dark brown in longitudinal section, consisting of densely intertwined, sclerotized hyphae. The outermost part of the stalk is +hyaline, with pale hyphae and a thin sheet of gelatinous material at the surface, often with a brownish or olivaceous tinge, or shiny black, and 0.08-0.13 mm wide.[2][3]

The capitulum is 0.21-0.28 mm in diameter and lens- or slightly bell-shaped. The exciple has an upper part that is often slightly translucent and pale, formed as a continuation of the stalk tissue, with isodiametric to slightly elongated and anti-clinally arranged, heavily sclerotized cells. The hypothecium is flat or slightly convex.[2][3]

The asci are 44 x 4-5 μm, cylindrical, and have uniseriate spores. The ascospores are semi-mature without ornamentation, but mature spores are ellipsoid, 11-15 x 5-7 μm, with irregular ornamentation of small pustules (minutely warted) giving rise to a dotted appearance under a light microscope, sometimes with a few irregular cracks.[2]

Spot tests show the thallus is K-, C-, KC-, P-, and the apothecia are I-.[2]

Calicium abietinum grows on wood, especially conifers and oaks, as well as on decaying stumps and logs, in the fringe areas of forests in moderate to rather strong light.[2]

Its known distribution includes Europe, North America, Central America, South America,[1] and Australasia.[4] In the Sonoran region, it has been recorded from Arizona and the Channel Islands of California.[2]