Phylloblastia inexpectata
Thallus on living leaves, often mainly along the main nerves, usually < 5 mm diam., very thin (no more than 15-25 μm thick), inconspicuous, brownish green or grey-green, often with a pink tinge, smooth, composed of a single layer of net-like branched mycelium with cylindrical to irregular cells, becoming broader and more irregular as the colony matures and the interstices between the branches contract. Isidia and soralia absent; occasional soredia may be seen on the thallus but these are probably dispersal propagules from another species. Photobiont a green alga with irregularly rounded aggregates of cells.
Anamorph: not known.
Teleomorph: ascomata perithecia, 100-150 µm diam. and <100 µm high, developing underneath the mycelial mat; shallowly domed to hemispherical, appearing applanately wart-shaped, pink-brown to almost black, sometimes with a darker red tinge around the ostiole, covered by a thin algal layer until mature. Periphyses always present, made of a layer of cells with conical-ovoid apices. Asci 40-48 × ca 15 μm, clavate or obovoid, with a thin wall except at the apex which is substantially thickened when immature, the wall K/I– but protoplasm typically K/I red-brown, 8-spored. Ascospores (10-)14-16 × (4-) 4.5-5 μm, very variable in both shape and septation, fusiform-ellipsoidal to cylindric-ellipsoidal, initially 0- or 1-septate but usually becoming 3-septate when mature, the upper median and distal cells slightly broader, with rounded ends, hyaline, smooth- and thin-walled, without an epispore, gelatinous sheath or appendages.
Evaluated by Woods & Coppins (2012) as of Least Concern. At the time of assessment there were few records and the species was thus designated as Nationally Scarce, but it now appears to be quite widely distributed and would not achieve that status.
Similar to Phylloblastia fortuita, but the ascospores have fewer septa and are not partially muriform.
On long-lived (evergreen) leaves, including Rhododendron ponticum, Prunus laurocerasus and Buxus sempervirens.
Scattered throughout southern England and Wales, also frequently encountered in central Scotland. BLS map.