Thelotrema nostalgicum
Thelotrema nostalgicum is a species of corticolous lichen in the family Graphidaceae. It has a pale, shiny thallus and hemispherical fruiting bodies with colourless, highly segmented ascospores. It was described from bark-growing material collected in Sri Lanka and is known only from that country.
Taxonomy
Thelotrema nostalgicum was described as a new species by the British lichenologist George Salisbury in 1972, in a revision of Thelotrema sect. Thelotrema. The holotype was collected on bark at Pidurutalagala in Ceylon in 1879 by Almquist and is preserved in the [William William Nylander (botanist)|Nylander (botanist)|Nylander] herbarium at H. Salisbury noted that Nylander had earlier placed the type specimen under Thelotrema dolichotatum, but considered it distinct and stated that T. dolichotatum belongs to the T. cavatum group ; Thelotrema cavatum is now known as Ocellularia cavata. In Salisbury's arrangement, T. nostalgicum was included in the T. lepadinum group and has colourless, septate spores.
Description
The thallus of Thelotrema nostalgicum is pale ochraceous and slightly shiny, 60–140 micrometres thick, with a somewhat cartilaginous about 15 μm thick; crystals were reported between the hyphae, and the algal partner was identified as Trentepohlia. The fruiting bodies are hemispherical and frequent, 0.6–0.7 mm across, each with a small, pore-like opening up to about 0.1 mm wide and an incurved. The is colourless and detached and bears on the inner face; the hymenium is 220–240 μm tall, and the ascospores are colourless, oblong-fusiform, and 27–34-septate, typically 2–3 per ascus, measuring 120–215 × 20–27 μm, with a purple iodine staining reaction.
Habitat and distribution
The type collection was collected on bark at Pidurutalagala in Ceylon, and Salisbury reported the species only from Ceylon.