Chaenotheca stemonea (Ach.) Müll.Arg.
*Account prepared by Dr L. Tibell (Uppsala).
Calicium stemoneum Ach., K. Vet. Acad. Handl. 1816: 278 (1816).
Thallus thin, farinaceous, consisting of a thin algal layer loosely entangled by mycobiont hyphae, glaucous green. Photobiont: Stichococcus. Apothecia short to medium-sized, 0.8-1.4 mm high, 11-19 times as high as width of stalk. Stalk 0.06-0.10 mm diam., in upper part whitish to dull brownish, in lower part dark brown to black. Capitulum spherical, with poorly-developed excipulum. The excipulum forms an inconspicuous collar at the base of the capitulum and is not visible from above. The brownish tinge of the lower side of the capitulum is caused by spores entangled in a loose hyphal web, that covers the lower side of the excipulum. This hyphal web also renders the excipulum a pale colour. Hypothecium with strongly convex upper surface. Asci cylindrical or irregular, with uniseriate or in part biseriate spores, 9-14 × 1.6-2.7 µm. Asci formed in chains. Ascospores spherical, 3.5-4.9 µm diam., smooth though a few irregular cracks also occur. Chemistry: The thallus contains two unidentified aromatic aldehydes giving a Pd+ yellow to reddish reaction. Thallus otherwise K-, C-, KC-.
N: South Auckland, Gisborne, Taranaki, Wellington. S: Canterbury, Otago, Southland. Rather rare on decorticated stumps, particularly of Nothofagus, more rarely on bark of Nothofagus and Libocedrus. Occurring in sheltered, humid and shaded situations, 100-1250 m.
Cosmopolitan
C. stemonea is widely distributed in the Northern Boreal - Temperate Zones of the Northern Hemisphere.
