Infections causing galls and eventually necrosis, the upper cortex of the host thallus breaking down, algal cells of the host partially killed by the parasite. Anamorph: not known. Teleomorph: ascomata perithecia, immersed in gall tissue with only the dark ostioles visible, 180-240 µm diam., spherical or very broadly pyriform. Peridium 20-30 μm thick, brown, composed of 4-5 layers of slightly tangentially flattened cells 12-15 x 4-5 μm in size, strongly pigmented in the ostiolar area. Interascal tissue composed of broad thin-walled paraphyses 3-5 µm diam., evanescent in older ascomata. Periphyses dense, multi-layered, ca 30 μm long and 2-4 μm diam., the terminal cells tapered and longer than the basal, with externally swelling walls, the uppermost periphyses often slightly browned. Asci broadly cylindrical or slightly clavate, very thin-walled, not fissitunicate, no apical structure visible, not blueing in iodine, usually 8-spored. Ascospores 15-18 x 5-7 µm, ellipsoidal to cylindric-ellispoidal, hyaline, 1-septate, smooth, thin-walled, without an epispore or gelatinous sheath.