Collema ryssoleum (Tuck.) A. Schneid.

    Thallus foliose, formed of membranous lobes, subgelatinous in wet weather, 1-6 cm in diameter. Lobes 0.5-1 cm wide with a rounded tip, upper surface coarsely wrinkled or with pustules, blackish in dry weather, dark olive green in wet weather, sometimes yellowish brown in old parts, no isidia; lower surface yellowish brown with whitish hapters. Apothecia lecanorine, sometimes abundant, 0.5-1 mm in diameter, flat disc reddish-brown, blackish-red to blackish, margin thin, entire, persistent. Asci 8-spored, apical dome I+ blue. Ascus hyaline, long fusiform with pointed tips, straight or slightly curved, 4-7 -septate, 22-47 x 4-11 µm. Frequent pycnidia immersed in the thallus. Photobiont: Nostoc. No significant coloured chemical reactions. Mediterranean saxicolous species growing on slightly acidic and humid siliceous rocks.

N.B. Appearance of Collema flaccidum but with apothecia and without isidia (Sometimes with this species on the same rock!).

_ Appearance also of Collema furfuraceum but this last species has more pleated lobes and is isidiate.