Byssoloma leucoblepharum (Nyl.) Vain.
Thallus 1-3 cm diam., continuous, usually thin, sometimes rather thick, minutely granulose or irregularly farinose, more or less cracked; greenish grey to brown greenish, prothallus inconspicuous to weakly developed, blackish. Apothecia scattered over thallus or sometimes clustered in groups and becoming ± distorted, 0,3-0,5 mm de diam., disc flat or weakly convex, orange-brown at first to brown, then dark brown and finally blackish; appear as discs lying on a coton layer with a tomentose yellowish white to yellowish grey arachnoid margin, composed of a network of translucid hyphae. The resulting design suggests an eye surounded with white, and explains the latin name. Utriform asci 35-40 x 13-16 µm according to our measurements. Colorless spores, elliptical with rounded ends and sometimes a slightly wider end, 2-3-septate, 10-18 x 2.5-4 µm according to the literature, 11-16 x 3-4 µm according to our measurements. Conidia abundant ± pyriform. Photobiont : Chlorococcales. Chemical spot tests negative but sometimes thallus Pd+ red-orange. Tropical species at the North extension limit in the oceanic zone of our prospection areas. On bark at the base of old trees (oaks) of oceanic forests. Mentioned on old Calluna stems in the literature.
N.B. Species taken here in the broad sense and including Byssoloma maderense which can only be distinguished by examination under a polarizing microscope.
In our prsopection area, another very similar species but much smaller, Byssoloma subdiscordans, may be found on leaves of evergreen trees and shrubs of Buxus and Abies. Their apothecia are darker, almost black and their thalli less thick and less emerald green.