Description
The thallus of Reichlingia lichens range in colour from white and pale grey to a greyish green. This main body of the lichen is usually compact, felt-like, and sometimes appears byssoid (resembling fine fibres) or granular in texture. Around the edges, a faint, whitish, hair-like prothallus may be visible, although when it encounters other lichens, a darker brown boundary line often forms. [4]
The lichen's photosynthetic partner ( photobiont ) belongs to Trentepohlia , a genus of green algae. Its reproductive structures, the apothecia, vary in shape—from round and polygonal to short and slit-like ( lirelliform )—and may form small, lobed clusters or irregular, star-like patterns. These structures lie either flush with the thallus or sit atop it, and they are often partly covered by a thin, whitish powder ( pruina ). The apothecia lack a clearly defined thalline margin , or if present, it is patchy and thin. Beneath the pruina, the tissue can be pale to mid-brown, and the supportive " true exciple " (the boundary around the apothecium) often narrows near the base. In some species, pale granular crystals are present within this exciple, while in others they are absent. [4]
Just below the surface, the epithecium (the top layer of the spore-producing region) may appear greyish due to the presence of pale crystals, or it can be dark brown. This layer consists mainly of densely branched, interwoven, thread-like structures ( paraphysoids ) that are largely free at their tips. The main spore-bearing layer (the hymenium) is generally colourless, supported by a hypothecium that can range from colourless to slightly brownish. The paraphysoids themselves branch loosely and are connected in a gelatinous matrix, with their tips occasionally darkened by brown pigments. The asci (spore-producing cells) are club-shaped and resemble those found in the Arthonia group. They typically contain eight spores and do not show a strong blue reaction with iodine-based staining (KI+). [4]
As the ascospores mature, they remain colourless or may turn pale brown. They are generally cylindrical or slightly egg-shaped, divided into three to five segments by internal walls, sometimes with larger end segments, or are partially subdivided into multiple small chambers ( submuriform ). The gelatinous matrix of the hymenium changes colour when tested with iodine solutions, typically turning deep blue or, less frequently, pale yellowish-brown to pale blue. [4]
So far, no pycnidia (another type of spore-producing structure) have been observed in Reichlingia. However, the type species (R. leopoldii) forms sporodochia —reddish to dark chocolate-brown spore-producing patches that can merge into large, irregular areas. Within these, the conidiophores (specialised spore-producing filaments) are dark brown with thick, warty walls. The resulting conidia (asexual spores) are also dark brown, irregularly branched, and have a warty surface, often visibly pinched at their internal divisions. [4]
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