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Arthonia molendoi (Frauenf.) R. Sant.
Family: Arthoniaceae
[Tichothecium molendoi Heufl. ex Frauenf.]
Arthonia molendoi image
Life habit: lichenicolous, on thalli and ascomata of Caloplaca and Xanthoria species Thallus: inapparent, vegetative hyphae in the algal layer photobiont: absent Ascomata: single or in small fusing groups, developing in the cortex (usually with host remnants on young stages), ±round, adnate, 0.1-0.24 mm wide disc: black, convex, rough to smooth surface epihymenium: olivaceous brown, 15-20 µm thick; cells: 3-4 µm wide, richly branched hymenium: hyaline, 45-50 µm tall, interascal hyphae branched and anastomosing, about 2 µm wide; subhymenium: medium brown, 50-60 µm thick, cloddy in the intercellular spaces, brown pigments in intercellular spaces asci: clavate, 35-43 x 17-20 µm, 8-spored, with thin lateral walls ascospores: hyaline, 1-septate, lower cell slightly attenuated, 11-14 x 5-6.5 µm, with a gelatinous epispore Pycnidia: not observed Chemical reactions: ascomatal gels I+ red, KI+ blue; asci with KI+ blue ring-structure; epispore I+ red, KI- Substrate and ecology: see the host species World distribution: subcosmopolitan Sonoran distribution: southern California (San Nicolas Island) and Arizona (Coconino Co., Graham Co.). Notes: Careful studies are still needed in the future to check whether specimens on different lineages in Caloplaca and Xanthoria belong to the same species.