Scytinium is a genus of lichen-forming fungi in the family Collemataceae.[2] It has 49 species.[3] These lichens are typically found on basic rocks, soil, and trees, occasionally in association with mosses. Despite the morphological and ecological diversity within Scytinium, its species share similar ascospore features, such as shape and septation, as well as a small to medium-sized thallus with at least a partial cortex .[4]
Scytinium encompasses lichen species that exhibit a variety of thallus forms, such as crustose, squamulose, minutely foliose , or minutely shrubby . These lichens have a gelatinous texture, and their colour ranges from dark brown and bluish-grey to olive-green. The lobes of Scytinium can be spreading, elongate, or somewhat cylindrical in shape. The upper and lower cortex , when present, is composed of either cuboid cells or flattened, degraded tissue. The medulla contains loosely interwoven or compact hyphae, along with the photobiont Nostoc–a common genus of cyanobacteria.[4]
An apothecial section of Scytinium gelatinosum shows some characteristics of the genus: a raised, red-brown, cup-shaped true exciple ; a red-brown, concave disc ; and ellipsoid, muriform ascospores
Both the upper and lower surfaces of Scytinium lichens can vary from smooth to wrinkled or ridged and typically exhibit a matte appearance. While isidia may or may not be present, soredia are absent in this genus. The photobiont cells are generally arranged in distinct chains. The ascomata are in the form of apothecia with a red-brown disc , which can be sessile, laminal, or marginal. The thalline margin is smooth to granulose , isidiate to lobulate , and often persistent. The true exciple is raised, cup-shaped, and predominantly composed of isodiametric cells, ranging in colour from colourless to reddish-brown. The disc is either concave or flat.[4]
The epithecium is colourless to reddish-brown and does not react with a solution of potassium hydroxide or ammonia. The hymenium is colourless, turning blue when exposed to iodine. The hypothecium is shallow, and its colour varies from colourless to pale yellowish. The hamathecium consists of numerous, conglutinateparaphyses that separate in potassium hydroxide and sometimes have branched apices that are somewhat swollen. The asci contain eight spores and are club-shaped (clavate), with a strongly thickened apex that reacts to potassium hydroxide and iodine, turning blue. Ascospores are primarily ellipsoidal, muriform , and colourless, lacking any distinct surface ornamentation or perispore . Conidiomata , or pycnidia , are infrequent in Scytinium species. No lichen products have been detected in Scytinium species using thin-layer chromatography.[4]
1 2 3 4 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 [27]. doi:10.34885/174.
↑ McCune, Bruce; Stone, Daphne F. (2022). "Eight new combinations of North American macrolichens". Evansia. 39 (3): 123–128. doi:10.1639/0747-9859-39.3.123.
↑ McCarthy, P.M. (2017). "A new species of Scytinium (Ach.) Gray (lichenized Ascomycota, Collemataceae) from the Australian Capital Territory". Australasian Lichenology. 80: 53–57.
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