Synonyms: Blastenia assigena Arnold; Caloplaca asserigena (J. Lahm) Della Torre & Sarnth.; Caloplaca assigena (Arnold) Dalla Torre & Sarnth.
Distribution: N - Frl.
Description: Thallus crustose, endosubstratic or thinly episubstratic and continuous to cracked, grey (rarely brown or brownish black), forming small paches to 7 mm in diam., densely covered with apothecia. Apothecia common, often crowded, 0.2-0.5 mm across, with a flat, rusty-red to finally blackish, pruinose disc and an hardly raised, thin, irregular, finally excluded, grey-white margin. Epithecium brownish red, granular, K+ red; hymenium colourless or yellowish, K- or K+ slightly purple, 50-60(-70) µm high; paraphyses branched in upper part, c. 1.5 µm thick at base, the apical cells up to 4.5 µm wide; hypothecium colourless. Asci 8-spored, clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, ellipsoid, 9-14 x 5-7(-7.5) µm, the septum 3-6 µm thick (1/3-1/4 of spore length). Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-; apothecial disc K+ red. Chemistry: thallus without lichen substances; apothecia with neochloroemodin.
Note: this species, related to a group of Southern Hemisphere Teloschistaceae, seems to be quite common in eu-oceanic habitats of Eurasia (Macaronesia, Norway, Caucasus), and also in foggy forests, usually on twigs of conifers or shrubs; in Italy it is evidently rare.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)