Fungi named in 1803

Cetraria islandica, also known as true Iceland lichen or Iceland moss, is an Arctic-alpine lichen whose erect or upright, leaflike habit gives it the appearance of a moss, where its name likely comes from.

Parmelia is a genus of medium to large foliose (leafy) lichens. It has a global distribution, extending from the Arctic to the Antarctic continent but concentrated in temperate regions. There are about 40 species in Parmelia. In recent decades, the once large genus Parmelia has been divided into a number of smaller genera according to thallus morphology and phylogenetic relatedness. It is a foliaceous lichen, resembling a leaf in shape. The ends of the leaf-like lobes are often squarish-tipped. The upper surface is pale bluish-gray to light brown in direct sunlight, with a network web-like

Cetraria is a genus of fruticose lichens that associate with green algae as photobionts. Most species are found at high latitudes, occurring on sand or heath, and are characterised by their "strap-like" form with spiny lobe edges. The lobes can range from narrow and linear to broader and flattened, often forming loose or densely packed cushions. Their distinctive spiny margins serve both a defensive role and aid in vegetative reproduction through fragmentation. The genus was created by Erik Acharius in 1803 and belongs to the large family Parmeliaceae. While originally a species-rich genus,

Physcia is a genus of lichen-forming fungi in the family Physciaceae. The widely distributed genus contains about 80 species. The genus is cosmopolitan, and has been extensively studied in various regions in the past several decades, with significant biodiversity in South America identified as a central diversity hotspot. Physcia species are foliose, lobate lichens that grow with a loose to close appressed habit. Their upper surface is typically whitish, pale greenish, green-grey, or dark grey in colour. The thallus colour remains relatively unchanged when moistened. Physcia lichens typically

Parmelia saxatilis, commonly known as the salted shield lichen or crottle, is a species of foliose lichen in the family Parmeliaceae. Several morphologically similar species, formerly lumped together, are now distinguished by their DNA.

Lepraria is a genus of leprose (powdery) crustose lichens that grows on its substrate like patches of granular, caked up, mealy dust grains. Members of the genus are commonly called dust lichens. The main vegetative body (thallus) is made of patches of soredia (little balls of algae wrapped in fungus). Sexual structures have not been observed in Lepraria, but genomic evidence indicates that the genus retains mating type and meiosis-associated genes, raising the possibility of cryptic sexual or parasexual recombination. Some species can form marginal lobes and appear squamulose. Because of the

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Lepraria incana is a species of dust lichen in the family Stereocaulaceae. First described scientifically by Johann Jacob Dillenius in 1741, and then formally by Carl Linnaeus in 1753, it is the type species of the genus Lepraria. The thallus of this species is green to greyish-green, and powdery – as if made of tiny granules. These granules are soredia, which are asexual reproductive structures. Like most members of genus Lepraria, the lichen has few distinguishing features, lacking both a medulla and sexual reproductive structures (apothecia). Chemically, the lichen is characterised by the

Lecidea is a genus of crustose lichens with a carbon-black ring or outer margin (exciple) around the fruiting body disc (apothecium), usually (or always) found growing on (saxicolous) or in (endolithic) rock. Lichens that have such a black exciple are called lecideine, meaning "like Lecidea, even if they are not in this genus. Members of the genus are commonly called disk lichens or tile lichens.

Thelotrema is a genus of lichen-forming fungi in the family Graphidaceae, the family to which all taxa in the former Thelotremataceae now belong. Members of the genus Thelotrema are commonly called barnacle lichens.

Cetraria sepincola, the chestnut wrinkle-lichen, is a species of foliose lichen in the family Parmeliaceae. It forms compact, cushion-like colonies typically 0.5–2 cm (1⁄4–3⁄4 in) high, with a yellowish-green to dark brown upper surface and lighter underside. The species has a primarily circumboreal distribution and is widespread in northern regions, occurring from Alaska to northern California in North America and documented as far south as Argentina. While mainly found growing on woody species like Betula, Sorbus, Salix, and Alnus in bog environments and open areas, it can occasionally be

Verrucaria viridula is a common and widely distributed species of saxicolous (rock-dwelling), crustose lichen in the family Verrucariaceae. Although it is a somewhat morphologically variable species, two persistent distinguishing characteristics are its relatively large perithecia, which are often curved into a beak, and its large ascospores.

Sticta is a genus of lichens in the family Peltigeraceae. The genus has a widespread distribution, especially in tropical areas, and includes about 114 species. These lichens have a leafy appearance, and are colored brown or black. Sticta species with cyanobacteria as photobionts can fix nitrogen from the atmosphere, and due to their relative abundance and high turnover, they contribute appreciably to the rainforest ecosystem. They are commonly called spotted felt lichens.

Psoroma is a genus of lichen-forming fungi in the family Pannariaceae. The widespread genus contains about 30 species, most of which are found in south temperate regions.

Calicium glaucellum is a crustose lichen that is found growing on trees throughout much of the world. The species is similar to Calicium abietinum. The species is commonly found in northern boreal to temperate zones in North, Central, and South America and the South West region of Western Australia.

Verrucaria muralis is a species of saxicolous (rock-dwelling, crustose lichen in the family Verrucariaceae. It is a common species with an almost cosmopolitan distribution, occurring in an altitudinal range extending from the lowlands to the subalpine zone. It grows on calcareous rocks and walls. It was first formally described as a new species in 1803 by Swedish lichenologist Erik Acharius.

Umbilicaria vellea is a species of lichen-forming fungus in the genus Umbilicaria. It is sometimes called navel lichen. It is found in North America and Europe in alpine and arctic habitats. It is similar to the species Umbilicaria americana, which has a more southern distribution. In Nepal, Umbilicaria vellea has been reported from 3,600 to 5,050 m elevation in a compilation of published records; this reported range extends above the tree line used in the study. In Iceland, it is found at only one location and is listed as an endangered species (EN).

Thelotrema lepadinum is a species of crustose lichen in the family Graphidaceae. Commonly known as bark barnacles, it forms a greyish crust on tree bark, dotted with numerous small, urn-shaped fruiting bodies that have distinctive white-rimmed openings. The lichen is found worldwide on smooth-barked deciduous trees, and in Europe it serves as an indicator of ancient woodland due to its preference for long-undisturbed forests. First described by the Swedish lichenologist Erik Acharius in 1799, the species has been reclassified multiple times throughout its taxonomic history.

Parmelia omphalodes is a species of foliose lichen in the family Parmeliaceae. It is one of the several dozen lichen species first described in 1753 by Carl Linnaeus. Swedish lichenologist Erik Acharius transferred it to the genus Parmelia in 1803. The lichen is widely distributed, having been recorded in Asia, Africa, Europe, and North and South Americas. In Nepal, Parmelia omphalodes has been reported from 3,500 to 4,500 m elevation in a compilation of published records; this reported range extends above the tree line used in the study. Morphologically similar–but genetically

Opegrapha vulgata is a species of corticolous (bark-dwelling) script lichen in the family Opegraphaceae. It was first scientifically described by Swedish lichenologist Erik Acharius in 1798, as Lichen vulgata. He transferred it to the genus Opegrapha in 1803. The lichen has a cosmopolitan distribution, and grows on the bark of a wide variety of tree species. Opegrapha niveoatra is similar in appearance, but can be distinguished form O. vulgata by its longer, curved conidia. O. lithygra is another lookalike, but it grows on rocks instead of bark.

Lecidea lapicida is a species of lichen in the family Lecideaceae. It has a worldwide distribution but it is rare in the tropics. Lecidea lapicida is a known host species to the lichenicolous fungus species Muellerella erratica, Muellerella pygmaea and Rhizocarpon furax.

Cornicularia is a genus of lichenised ascomycetes in the large family Parmeliaceae. It is a monotypic genus, with a single currently accepted species, the saxicolous lichen Cornicularia normoerica, and is sometimes referred to as the bootstrap lichen. The lichen forms small, dark tufts rarely exceeding 2 cm in height that are anchored so firmly to rocks, with narrow, stiff branches topped by shiny black reproductive discs. It grows on high-elevation, sun-exposed rocks and boulders, where its compact, shrub-like appearance and glossy black-brown surface make it distinctive among mountain

Lecidea fuscoatra is a species of saxicolous (rock-dwelling) crustose lichen in the family Lecideaceae. This widespread species is found across Europe, North America, North Africa, and Asia. First described by Carl Linnaeus in 1753, it forms a thin crust that breaks into small, shiny, tile-like patches ranging from whitish grey to pale brown, typically outlined by a black border of fungal tissue. The lichen produces small black disc-shaped fruiting bodies that are often nestled between the crustal patches and contain eight colourless ascospores per spore sac. It grows primarily on acidic

Bathelium is a genus of lichen-forming fungi in the family Trypetheliaceae.

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Calicium corynellum is a species of pin lichen in the family Caliciaceae. It is found scattered across parts of Europe, North America, and Asia, where it grows on rock surfaces in shaded and humid locations.