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Page number:6 
Description type:Non-original description 
Description:Cercidospora Körb. emend. Hafellner Parerga Lichenologica: 465 (1865) and Herzogia 7: 354 (1987).
Type species: Cercidospora ulothii Körb. [syn. Cercidospora macrospora (Uloth) Hafellner & Nav.-Ros.].
The genus Cercidospora comprises only lichenicolous fungi with ascomata immersed in the host thallus or apothecia. Exceptionally, deformations in form of cecidia in which ascomata are grouped can be observed.
The ascomata are perithecioid (pseudothecia), externally blackish, smooth, ostiolated, variable in size in the different species, and more or less immersed in the host thallus. The peridial wall is usually intensely pigmented near the ostiolum, this pigment being amorphous and variable in color, from bluegreen to violet-brown or blackish; in contrast, the basal part of the ascomata is generally colorless, although in some taxa, it may be more or less pigmented. The wall is formed by thin hyphae, with much reduced cells that do not form a clearly prosoplectenchymatic structure, rather recalling the so-called textura intricata (Hawksworth et al. 1983). Between the fungal ascomata and host thallus, a colorless layer formed by cells with a reduced lumen can frequently be observed.
The hamathecium is formed by paraphysoids, the abundance of which is variable in the different taxa. They are filiform, septate, simple or with some anastomoses.
The asci are typically fissitunicate, cylindrical, or cylindrical-clavate, with the endoascus apically slightly thickened and provided with a small ocular chamber. They contain a variable amount of ascospores depending on the different taxa, ranging from 2 to 8 per ascus.
The ascospores are colorless, with one or more transversal septa in most species and simple only in C. lobothalliae; their form is oval, ellipsoid or fusiform, heteropolar or not, strongly heteropolar in some taxa. The occurrence of a perispore in the form of a thin gelatinous sheath is characteristic; this character is especially visible in young ascospores.
Diagnostic for the genus are the pigmentation and texture of the peridium, the persistent paraphysoids, the fissitunicate cylindrical asci, and the hyaline ascospores with a thin perispore. Infrageneric variables important for distinguishing species are mainly the color of the peridial pigment, the number of ascospores per ascus, the ascospore shape and number of septa, quantitative characters of all parts of the ascomata and host selection.
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