Anamorph: conidial production sometimes visible as a powdery surface of the stroma, forming a closely packed palisade of percurrently proliferating conidiogenous cells 26-38 x 6.5-7.5 µm in size. Conidia 9-11 µm diam., spherical, thick-walled, yellowish, aseptate, minutely asperulate, without a gelatinous sheath or appendages [some information from Cooke, 1952]. Previously known as Stromatocrea cerebriformis.
Teleomorph: stromata 15-35 (-110) mm diam. and 2-4 (-5) mm thick [fide Stasinska, 2004], irregularly radially ridged with branched finger-like projections to the periphery, orange-brown to pale brown or ochraceous, sometimes reddish, the outer parts often less strongly pigmented, initially smooth but becoming rugose in the central part and often with a farinose appearance due to production of conidia. Ascomata perithecia, immersed in stromatic tissue with the ostioles visible as brown dots over almost the entire stroma surface, ± globose, the neck papillate and hardly extending beyond the surface. Interascal tissue absent at least at maturity, though probably with apical paraphyses. Asci cylindrical, thin-walled, not fissitunicate, with a minute apical ring that does not blue in iodine, 6- to 8-spored. Ascospores arranged uniseriately, (16-) 18.5-23 x 7.5-10 µm, rather variable in form but mostly broadly fusiform to fusiform-ellipsoidal, the ends usually distinctly pointed, rather thick-walled, with a median septum, hyaline, minutely verrucose (ornamentation only visible easily using an oil immersion lens), without a gelatinous sheath or appendages, not aggregated in clusters when ejected.
Not formally assessed, but likely to be at least Vulnerable, or perhaps more appropriately Endangered. Listed as priority species for conservation in England and Wales.
There are only four confirmed sites for this species in GB&I in the last 50 years: two recently discovered sites in Scotland (Roxburghshire VC80, and Berwickshire VC81), and two in Wales (Radnorshire VC43 and Glamorgan VC41).
The Scottish populations appear to be comparatively healthy and viable at least in the short term. The Glamorgan site is relatively small and restricted, but regular surveillence is being undertaken. The Radnorshire population was last confirmed extant in 1989 and considered threatened by forestry operations, with the only known tree harbouring this fungus damaged by a falling spruce. Attempts to re-find that population in 2015 were unsuccessful, and this population is likely to have been lost.
Listed as a species of principal importance to the conservation of biodiversity under Section 41 (England) of the Natural Environment and Rural Communities (NERC) Act 2006; and Section 7 of the Environment (Wales) Act 2016.
Easily distinguished from H. rhododendri by its ascospores which are almost smooth and are not aggregated into clusters on ejection, by the presence of an anamorph [at some stages of stroma development], and by differences in its assumed host fungus (Hymenochaetopsis tabacina versus H. corrugata).
Considered to be a parasite of the resupinate fungus Hymenochaetopsis tabacina (=Hymenochaete tabacina), a wood-inhabiting species which is found primarily associated with Salix spp.
In GB&I, known definitely from two sites in Wales (Radnorshire VC43, although this site may have been lost in recent years; and Glamorgan VC41); and two sites in Scotland (Roxburghshire VC80, and Berwickshire VC81). Unconfirmed and unvouchered records from Kent and East Cornwall. Historically recorded from South Lincolnshire VC53, South-west Yorkshire VC63, Westmorland VC69, Cumberland VC70, Kirkcudbrightshire VC73, and Angus VC90.
The three confirmed recent populations have been found on dead branches in Salix woodland or carr, with Hymenochaetopsis tabacina present nearby. Populations may be more likely to occur on horizontal dead branches and twigs.