Sclerococcum parellarium
Conidial structures: not known.
Ascostromata (80–) 200–500 µm diam, apothecial, discoid, the larger ascomata rather irregular in outline, hardly stipitate, black, not pruinose, surrounded by a fairly broad concolorous excipular layer which sometimes appears verrucose due to the presence of minute knob-like projections. Ascomatal wall composed of a lower layer of thin-walled dark brown angular cells, merging into a pad-like structure of very thick-walled and apparently gelatinized cells with reduced lumina, which extends beyond the hymenium as the outer excipular layer. Hymenium 50–70 µm tall. Interascal tissue composed of hyaline paraphyses 2–2.5 µm diam., sparsely branched towards the slightly swollen apex, covered in a thick J+ gelatinous coat and with pigmented apices and a reddish brown epithecial layer. Asci 29–38 (–55) × 9.5–12 µm, cylindric-clavate, short-stalked, fairly thick-walled but not fissitunicate, without an apical pore, 8-spored, covered in a thick J+ gelatinous layer. Ascospores arranged biseriately, 8.5–11.5 (–13.5 when multiseptate) × 4.5–5.5 µm, broadly cylindrical with rounded ends to ellipsoidal, dark brown when mature, rather thick-walled, smooth, often slightly constricted at the ± median primary septum and sometimes with one or rarely two further transverse septa, without a gelatinous sheath or appendages.
Description adapted from Cannon (2010).
Assessed by Woods & Coppins (2012) as of Least Concern, but listed as Nationally Scarce.
S. parasiticum may also occur on Ochrolechia species, and is also reported from various Pertusaria s.l. species. It has slightly longer and narrower ascospores, typically with a larger number of septa. The two species need re-evaluation.
On thalli and apothecia of Ochrolechia parella.
Common throughout Scotland, also present in montane regions of Wales, and N and SW England.