Product Code Database
Lithographa is a genus of lichen-forming fungi in the family Xylographaceae. These rock-dwelling lichens form tightly attached crusts that crack into small tile-like patches, typically appearing in shades of grey, brown, or nearly black. The genus includes six species found primarily in cold regions and high mountains, where they grow on hard rock surfaces in harsh environments. They reproduce through distinctive elongated or round fruiting bodies that appear as dark slits or discs embedded in the crusty surface.
Rounded, sometimes gyrose apothecia in the related genus Lambiella set it apart from slit-disc Lithographa. Phylogenetic work places Lithographa in the same clade as bark-dwelling Ptychographa, and both differ from Wadeana, which has a weaker exciple, reddish apothecia and a filamentous green alga ( Trentepohlia) as its .
The reproductive bodies are apothecia that range from elongate, slit-like to small angular or round . They sit flush with, or slightly above, the thallus and never bear a ; instead, the visible border is a —a dark, opaque ring of densely fused that radiate outward from the base. The disc itself is a narrow, black fissure. Inside, the clear hymenium turns blue with iodine staining, a sign of amyloid material in the ascus walls, while a sparse mesh of branched paraphyses threads the spore layer. ascus are club-shaped and always eight-spored; when stained, the sides of the ascus apex turn dark blue, but a broad central plug remains unstained, a pattern shared with the Trapelia type. Mature are typically single-celled (aseptate), colourless and ; two southern-hemisphere species develop somewhat spores, although it is suspected that they may not belong to this genus. Many species also produce immersed pycnidia that release slender, rod-shaped conidia, but these structures are absent in the type species, L. tesserata.
|
|
