Calicium viride Pers.
Thallus crustose, rather thick, granulose, bright green, greenish, yellow-green turning to green-brownish when old. Often sterile and, in that case, hardly recognizable; otherwise with small apothecia, 0.2-0.7 mm diam., black in section, heads occasionally powdered in brown, on apices of stalks 1-2 mm high. Asci clavate, formed singly from ascogenous hyphae with croziers, dissolving at an early age. Ascospores ellipsoid, brown, surface with irregular cracks, 1-septate, constriction at septum level, brown-blackish, surface cracked to rugose (sometimes but seldom at full maturity, with spirally distributed winged excrescences), 11-14 x 4-5 µm according to literature, (10) 12-15 x 5-7 µm according to our measures. Photobiont : Trebouxia. Thallus: C-, K-, KC-, Pd-, UV+ bright orange. Rather common species (but often understated) on barks of deciduous trees or conifers. Some specimens with a green thallus, granulose, only partly developed may resemble Calicium salicinum, which has thinner thallus, cylindrical asci and smaller spirally wrinkled ascospores.