Thallus: a thin crust, almost inconspicuous, greyish white, usually immersed, ca 200 µm thick, not well delimited, with 7-10 µm diam., chlorococcoid algae as photobiont.
Anamorph: not known.
Teleomorph: Ascomata black, non-pruinose apothecia, appearing sessile, but with a short stalk no taller than 100 µm. Capitulum, bell-shaped, (195-) 235-400 (-500) µm diam., with a distinct dark brown mazaedium, which sometimes appears bluish-grey due to the presence of colourless thin hyphae amongst the ascospores. Exciple lecideine, carbonised, dark brown to black, 45-65 µm wide, consisting of tightly compressed isodiametric cells, with carbonised lumen, 4-5 µm diam., forming a prosoplectenchyma, non-continuous below the hypothecium. Hypothecium dark brown, becoming carbonised, 120 µm high at its widest point. Epithecium not observed. Asci cylindrical, ca 70 x 5-5.5 µm, but difficult to observe, unitunicate and soon evanescent, 8-spored. Ascospores broadly ellipsoidal, initially uniseriately arranged within the ascus, pale brown and aseptate, but when matured and forming the mazaedium become darker brown, 1-septate, only slightly constricted at the septum, thick walled and ornamented, (9-) 11-13 × 4-6 µm.
Chemistry: The species contains physodalic acid (a β-orcinol depsidone) as a major component, but this was detected only by HPLC analysis from the apothecia. All spot tests carried out on the thallus and apothecia were negative. The more characteristic lichen substances in the Caliciaceae such as pulvinic acid derivatives and anthraquinone could not be detected in this species.
Not formally assessed, but so far it is only known from a single locality in the south of England; the species is inconspicuous and may well have been overlooked.
The subsessile and mazaediate ascomata, and one-septate, ornamented ascospores are diagnostic characters of this species and of Calicium diploellum Nyl., but the latter has smaller ascomata and ascospores, and presents a yellow pruina when young. Ecologically C. diploellum appears to have an oceanic distribution as it is restricted to the NW of Scotland and the SW of Ireland where it is found on Ilex bark – not wood. Calicium victorianum resembles C. glaucellum both microscopically and chemically, but C. glaucellum has clearly stalked, taller apothecia, and a white pruinose exciple. Molecularly, and based on ITS and LSU nuclear rDNA sequences, both species belong to sister groups, though the support for this placement is weak. Neither species are in the same molecular clade as the type of Calicium, C. viride. Other oak inhabiting ‘calicioid’ species with sessile fruit bodies which could be confused with C. victorianum are Cyphelium inquinans which has larger ascospores and a well-developed superficial thallus, and Chaeonothecopsis retinens with smaller ascospores, reddish stalk and exciple, and lacking a mazaedium.
The species was first described from the Southern Hemisphere, and currently has a disjunct distribution; it is known only from Australia, New Zealand, and a single locality in West Sussex (England). BLS map here.
The species is found on wood and man-made materials, e.g. stumps or fencing posts, of species of Fagaceae (such as Nothofagus and Quercus spp) or Eucalyptus spp. In Britain it grows on the north face of vertical posts of an oak fence near a cleared woodland, positioned in full sun, but the species is not thriving.