Ceratosphaeria mycophila
Ascomata 300-350µm diam, the body ± globose, superficial or partially immersed, black, smooth, leathery; the neck strongly papillate, 50-80µm long, gradually tapering towards the apex, black. Peridium composed of outer layers of almost black textura epidermoidea, the cells rarely more than 4µm diam, merging into poorly-defined textura intricata in the neck region, and an inner layer of ± hyaline cells. Interascal tissue well-developed, composed of very thin-walled unbranched tapering paraphyses ca 3 µm diam. along most of their length, to 7 µm diam. near the base. Asci 200-230 x 11-12.5 µm, cylindrical with a long tapering stipe, fairly thin-walled, not fissitunicate, the apex rounded with a distinct refractive ring ca 2.5 µm diam. and 1-1.5 µm thick, 8-spored. Ascospores arranged biseriately, 41-52 x 4.3-5.3 µm, narrowly cylindrical, straight or slightly curved to sigmoid, 7-9 (-11) septate, the septa very thin and usually obscured by large guttules, not constricted at the septa, hyaline, thin- and smooth-walled, without a gelatinous sheath.
Easily distinguished by its elongate many-septate ascospores and conspicuous ascus apical ring, combined with relatively thin-walled leathery ascomata. The ascospore septa are sometimes difficult to observe as they are obscured by oil droplets. The species is certainly not typical of Ceratosphaeria and may need transferring elsewhere. Carroll & Munk (1964) considered that it belongs in Lasiosphaeria (Lasiosphaeriaceae), but the ascus apex is not typical of that family and Lasiosphaeria itself is polyphyletic as currently circumscribed. It may well belong to Paragaeumannomyces (Chaetosphaeriaceae); it is broadly similar to P. abietis except for ascospore length; see Réblová et al. (2020) for more details.
On very rotten wood of Fagus sylvatica, Fraxinus excelsior and Ilex aquifolium, presumably saprotrophic.
In GB&I: England: Surrey, Sussex. Scotland: Skye.