Staurothele fissa (Taylor) Zwackh

    Thallus crustose, continuous but most often cracked and areolate with sometimes more or less scaly areas, gray-brown a little olive in water, light brown to dark brown if dry, prothallus paler. Perithecia not homogeneously arranged but grouped together in certain areas of the thallus, prominent, conical with a base covered by the thallus and a blackish top with a paler ostiole. Involucrellum present. Hymenium with large colonies of subglobose algae (Stichococcus) of cubic appearance, 3-6 x 3-5 µm, single, double or by 4. Asci in clubs with (1) -2 spores, 87-105 x 28- 30 µm according to our measurements. Muriform spores, oblong, colorless then pale brown, 35-50 x 15-25 µm according to the literature, 35-47 x 16-20 µm according to our measurements. Pycnidia present, slightly curved pycnidiospores, 3-4 x 1-2 µm. Typically on siliceous rocks that are periodically inundated along riverside at average water level (but in waters that are not too acidic).