Caloplaca haematites
Thallus crustose, mid to dark grey, moderately thick, of coalescent convex granules but smooth towards the margin, unevenly areolate towards the centre, often surrounded by a broad, pale grey, blue-tinged prothallus.
Anamorph: not observed.
Teleomorph: Apothecia 400-700 (-1000) µm diam., rounded but sometimes angular by mutual compression, almost sessile and constricted at the base. Thalline margin pale to mid grey, smooth and swollen at first, becoming thinner or excluded when old. Disc brown-red, concave when young, becoming flat when mature. Interascal tissue composed of simple or forked septate paraphyses, broadening towards the tips, the apical cells ca 3 μm diam. Asci cylindrical to cylindric-clavate, short-stalked, the apical part sometimes slightly attenuated, the apex rounded and the wall strongly thickened, usually 8-spored. Ascospores 11-16 × 5-9 μm, ellipsoidal, polarilocular, the septum 1/4-1/2 or even more of the length of the ascospore, hyaline, without a perispore or gelatinous sheath.
Chemistry: thallus K–, apothecial discs K+ purple.
Currently assessed as Data Deficient (Woods & Coppins 2012). The species is potentially threatened, and has only been reported reliably on one occasion (in 2011) since the end of the nineteenth century. Further surveys would be highly desirable.
Rather similar to Caloplaca cerina, but with a reddish rather than yellow-orange disc with a margin that tends to become excluded in old apothecia.
In GB&I, known historically from VC3 S Devon, VC29 Cambridge and VC37 Worcester, with a single modern record from VC12 N Hampshire.
On smooth, base-rich bark, especially twigs of fruit trees, Juglans and Populus.