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Lathagrium

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Genus of lichen

Lathagrium
Lathagrium auriforme
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Lecanoromycetes
Order: Peltigerales
Family: Collemataceae
Genus: Lathagrium
(Ach.) Gray (1821)
Type species
Lathagrium undulatum
(Laurer ex Flot.) Poetsch (1872)
Synonyms
  • Collema subgen. Lathagrium Ach. (1810)

Lathagrium is a genus of lichen-forming fungi in the family Collemataceae. It has 10 species of gelatinous lichens. Species in this genus typically grow on calcareous rocks, often amidst mosses, but can also be found on siliceous or serpentine rocks, mortar, or soil.

Description

Lathagrium is characterized by a foliose, medium to large-sized thallus that can appear gelatinous and may swell when wet. The color of the upper surface ranges from dark olive-green to brown-black and occasionally exhibits a grey-blue hue. The lobes of the thallus can be narrow or broad, often elongated and intricately branched, with a flat or concave surface that can be smooth or distinctly ridged or folded.

The thallus is composed of intertwined hyphae intermingled with chains of photobiont cells, and it lacks both upper and lower cortex. While isidia can be absent or frequently present, soredia are not found in Lathagrium. The reproductive structures, called apothecia, display a pale brown, red-brown, or brown-black disc surrounded by a thalline margin that is typically long-lasting.

The internal structure of the apothecia consists of colourless or pigmented epithecium, a colorless hymenium that turns blue when treated with iodine, and a nearly colorless hypothecium. The hamathecium contains paraphyses that separate in a solution of potassium hydroxide and may be unbranched or branched, often connecting near the apices. The tips of the paraphyses can be club-shaped or round and display a yellowish to reddish-brown colour.

The asci, or spore-producing structures, are club-shaped (clavate) with a significantly thickened apex that reacts blue with iodine, as does the downwardly projecting annulus and apical cap. Lathagrium produces eight spores per ascus, which are septate and primarily submuriform, but can also be spindle-shaped or cylindrical with only transverse septa.

Conidiomata, or pycnidia, are generally embedded within the thallus and can be found on the margins or lamina with a pale ostiole. The conidia are rod-shaped and may be slightly enlarged at the apex. Chemical analysis using thin-layer chromatography has not detected any lichen products in Lathagrium.

Species

References

  1. "Lathagrium". Catalogue of Life. Species 2000: Leiden, the Netherlands. Retrieved 19 April 2023.
  2. Wijayawardene, Nalin; Hyde, Kevin; Al-Ani, Laith Khalil Tawfeeq; Somayeh, Dolatabadi; Stadler, Marc; Haelewaters, Danny; et al. (2020). "Outline of Fungi and fungus-like taxa". Mycosphere. 11: 1060–1456. doi:10.5943/mycosphere/11/1/8. hdl:10481/61998.
  3. ^ Cannon, Paul; Otálora, Mónica A.G.; Košuthová, Alica; Wedin, Mats; Aptroot, André; Coppins, Brian; Simkin, Janet (2020). "Peltigerales: Collemataceae, including the genera Blennothallia, Callome, Collema, Enchylium, Epiphloea, Lathagrium, Leptogium, Pseudoleptogium, Rostania and Scytinium". Revisions of British and Irish Lichens. 2: 1–38. doi:10.34885/174. Open access icon
Taxon identifiers
Lathagrium
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