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Brief Summary

    Graphis (lichen): Brief Summary
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    Graphis is a genus of lichenized fungi in the family Graphidaceae. According to the Dictionary of the Fungi (10th edition, 2008), the widespread genus contains 386 species.

    Graphidaceae is one of the most prevailing species in lichen communities, though its classification is not well developed.

    Previously, the graphidoid members of Graphidaceae sensu were divided into the genera Graphis, Graphina, Phaeographis, and Phaeographina, contingent on if the ascospores are septate or muriform, colorless or greyish brown. Septate in terms of mycology refers to the condition where there is a lack of partition dividing filamentous hyphae into discrete cells in fungi. This notion was thought of as synthetic and adjustments of Acanthothecis and Dyplolabia changed the method to a more natural generic classification of the family.

    A set of characteristics such as excipulum and hamathecium structure, ascospore color and iodine reaction, and chemistry, was suggested to reach a much more sufficient genus model. The excipulum is the cup shaped tissue that holds the hymenium, asci, in the apothecium. The hamathecium is the hypha emerging between the asci of the hymenium.

    Thallus color, thallus cortex, vegetative propagules, lirella emergence, thalline margine of lirella, relative length and branching of lirellae, disc exposure, labia and disc pruinosity, labium striation, excipulum carbonization, hymenium inspersion, and ascospores are all considered when characterizing Graphis.

    Thallus color – The majority of Graphis species have a large amount of calcium oxalate crystals in the photobiont layer and which results in a white-grey thallus. Some but few taxa have an olive-green color close to Phaeographis and other related species because the crystal clusters are located below the photobiont layer instead of in or above layer. Staining in the herbarium constituent is common and due to incorrect aeration causing breakdown of secondary substances. In these cases, a hand-cut section of the thallus aids to classify the thallus type and regular color. Thallus cortex – Species with a corticate thallus have a compact, slightly shiny exterior, whereas ecorticate taxa show a lusterless, coarse or farinose thallus under the dissecting microscope. If present, a cortex is recognized as a thin but characteristic, hyaline layer of condensed, parallel hyphae in hand-cut sections under the compound microscope. Vegetative propagules – Only four species have isidia and one has soralia which are powdery propagules composed of fungal hyphae. Isidia are the vegetative reproductive structures in lichens and are usually numerous in G. isidiata, G. isidiza, and G. patwardhanii, but scattered and easily overlooked in G. stellata, so vigilant examination of the thallus surface is necessary.
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