Synonyms: Bacidia atrogrisea (Delise) Körb.; Bacidia elevata Körb.; Bacidia endoleuca auct. non (Nyl.) J. Kickx f.; Bacidia subacerina subsp. laurocerasi (Duby) Vain.; Bacidia subacerina Vain.; Bacidia violacea (Arnold) Arnold non "(Crouan) Arnold"; Biatora atrogrisea Delise
Distribution: N - Frl, Ven (Thor & Nascimbene 2007, Nascimbene & al. 2013b), TAA (Nascimbene & al. 2007b), Lomb, Lig (E.C.I. 424: LD-1186694). C - Tosc, Umb (Ravera 2000, Ravera & al. 2006), Laz (Ravera 2006c), Mol (Ravera & Genovesi 2010, Ravera & al. 2010), Sar (Loi & al. 2000, Zedda 2002, 2002b, Rizzi & al. 2011, Cossu 2013, Neuwirth 2018, Di Nuzzo & al. 2022). S - Camp (Ricciardi & al. 2000), Cal (Puntillo 1996, Sérusiaux 1998), Si (Nimis & al. 1994, Ottonello & Puntillo 2009).
Description: ThaIlus crustose, episubstratic, continuous to rimose-areolate, grey to grey-green, sometimes delimited by a dark prothallus. Apothecia lecideine, (0.5-)0.5-0.8(-1.1) mm across, with a convex, usually epruinose, dark purple-brown to black, often mottled disc, and a concolorous or slightly paler, smooth, persistent or rarely excluded proper margin. Proper exciple 45-120 µm wide, without crystals or rarely with radiating clusters of crystals, brown or red-brown in upper and outer parts, pale yellow to colourless within, the pigmented parts K+ purplish; epithecium brown to black-brown, K+ purplish N+ orange-red, the pigment dissolved in the gelatinous matrix or as granules between apices of paraphyses; hymenium colourless or with brown vertical streaks, 75-115 µm high; paraphyses 0.8-1.6 µm thick at mid-level, the apical cells not swollen to clavate, (1.2-)2-3(-4) µm wide; hypothecium colourless or pale yellow. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall K/I-, but the thin outer gel K/I+ blue, Bacidia-type. Ascospores (2-)4-12-septate, hyaline, needle-like, straight to slightly curved, (32-)36-67(-73) x (2.5-)3-4(-4.3) µm. Pycnidia partly or entirely immersed, dark in uppermost part. Conidia simple, thread-like, curved, 5-10 x c. 1 µm. Photobiont chlorococcoid. Spot tests: thallus K- or rarely K+ yellowish, C-, KC-, P-. Chemistry: thallus without lichen substances or with traces of atranorin; epithecium, rim of proper exciple, and pycnidial wall with the Laurocerasi-brown pigment; hypothecium and inner part of proper exciple with the Rubella-orange pigment.
Note: a humid subtropical to Mediterranean-Atlantic lichen found on smooth bark of broad-leaved trees in open humid forests; most frequent in Tyrrhenian Italy. According to Ekman (in litt.) the species might have been confused with B. heterochroa in the past (see note to B. heterochroa).
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)