Thelomma A.Massal.
Type : Thelomma mammosum (Hepp) A.Massal. [=Cyphelium mammosum Hepp]
Description : Thallus crustose to placodioid, thin and smooth, to thick, warted, areolate, greyish, corticate Cortex composed of hyphae normal to the surface, sometimes with swollen and brownish apices. Photobiont green, trebouxoid. Ascomata apothecia, immersed in verrucae 0.8–2.5 mm diam., as wide as high. Exciple reduced laterally, very thin or forming a basal collar at edge of hypothecium. Hypothecium blackish brown, thick. Mazedium well-developed, black. Asci cylindrical, formed singly and disintegrating at an early stage. Ascospores simple to 1-septate, 8 per ascus, spherical to ellipsoidal, dark brown-black; spore wall thick, dark-brown, smooth or with minute to coarse irregular cracks or with faint parallel ridges. Conidiomata not seen.
Thelomma is included in the family Physciaceae nom. cons. (Wedin et al. 2002b; Wedin & Grube 2002), and closely resembles Cyphelium, which has sessile or immersed apothecia with a dark brown-black, laterally well developed exciple forming a distinctly raised rim, and 1-septate or submuriform ascospores in which the spore wall has concentrically arranged layers (TEM). The genus has seven species worldwide (Tibell & Ryan 2004g), mostly found on siliceous rocks or on lignum in the Northern Hemisphere, and is especially frequent in coastal areas with a Mediterranean climate. It is discussed in detail in Tibell (1976, 1984b, 1994) and Tibell & Ryan (2004g). One species occurs in New Zealand and is thought to be a recent introduction here (Tibell 1994).
