William Nylander

Hypogymnia is a genus of foliose lichens in the family Parmeliaceae. They are commonly known as tube lichens, bone lichens, or pillow lichens. Most species lack rhizines (root-like attachment organs on the lower surface) that are otherwise common in members of the Parmeliaceae, and have swollen lobes that are usually hollow. Other common characteristics are relatively small spores and the presence of physodic acid and related lichen products. The lichens usually grow on the bark and wood of coniferous trees. Hypogymnia was proposed by lichenologist William Nylander, first as a subgenus of

Hypogymnia physodes, commonly known as the monk's-hood lichen, is a species of foliose lichen in the family Parmeliaceae. It is a common and widespread species in boreal and temperate forests of the Northern Hemisphere. It has a grey to yellowish-green thallus that is loosely attached to its substrate and forms large irregular patches. Hollow lobes are 2–3mm wide. The outer edge turns up and is frequently covered with white powdery soredia underneath. Its lower surface is black, wrinkled and has some browning toward the lobe margins. The pycnidia are black and abundant, and their presence

Physcia stellaris is a species of lichen. It is pale grey, but darker in the centre, and lacks isidia, lobules, soredia and pruina.It tests positive K+ yellow upper cortex with a 10% potassium hydroxide solution. In North America, it is known colloquially as the fringed rosette lichen. It can grow as an epiphyte. In Greece, it has been reported from the trunk of Platanus trees.

The Lichinaceae are a family of ascomycete fungi in the order Lichinales. Most species are lichenized with cyanobacteria, and have a distribution largely in temperate regions. In a 2024 molecular phylogenetics-informed revision, the circumscription of Lichinaceae was narrowed and the class Lichinomycetes was re‑structured into four families (three emended and one new), with many genera moved to Porocyphaceae, Phylliscaceae, or the newly erected Lichinellaceae. The family contain about 125 species in roughly 25 genera.

Peltigera membranacea is a species of lichenized fungus in the family Peltigeraceae. It has a foliose growth pattern, with what appear to be veins in the leaf-like parts, but these do not have a vascular function. The apothecia are erect, numerous, and often a bright brown-orange in colour. Some simple sequence repeat markers have been developed for both the fungal partner (mycobiont) of Peltigera membranacea and its Nostoc photobiont partner; these allow for both population genetic studies and an alternative means of identifying between P. membranacea and its lookalikes. In Nepal, Peltigera

Solorina bispora is a species of foliose lichen in the family Peltigeraceae. It has a circumpolar distribution, occurring in arctic and alpine environments where it grows on humus-rich soils and in rock crevices.

Parmeliopsis is a genus of lichens in the family Parmeliaceae. The genus contains two species. Members of this genus are commonly called bran lichens.

Leptogium saturninum is a species of lichen-forming fungus belonging to the family Collemataceae. It has cosmopolitan distribution. In Nepal, Leptogium saturninum has been reported from 1,500 to 2,100 m elevation in a compilation of published records.

Evernia mesomorpha is a species of lichen belonging to the family Parmeliaceae. It has a cosmopolitan distribution.

Thelopsis is a genus of lichen-forming fungi in the family Gyalectaceae. The genus was established by the Finnish lichenologist William Nylander in 1855 and contains small bark-dwelling crustose lichens that form thin crusts on surfaces. These lichens make flask-shaped fruiting bodies called perithecia, which contain numerous small ascospores divided by cross-walls. Recent molecular studies have revealed that the genus forms a closely related group within the broader Gyalecta complex, leading to taxonomic revisions that now recognise about a dozen species worldwide.

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Thelocarpon is a genus of lichen-forming fungi in the family Thelocarpaceae. The genus was established in 1853 by the Finnish lichenologist William Nylander, who distinguished it from related genera by its warted thallus structure, many-spored asci, and the distinctive violet-blue staining reaction of its fruiting body gel when treated with iodine. These tiny lichens form small, wart-like bumps on soil, wood, and plant debris, often covered with a distinctive bright yellow powdery coating. The genus includes about 30 species found worldwide, many of which produce unusually large numbers of

Ramalina thrausta is a species of fruticose lichen belonging to the family Ramalinaceae. It is found in Europe and Northern America.

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Normandina pulchella, commonly known as the elf-ear lichen or blue heart, is a species of squamulose lichen in the family Verrucariaceae. This cosmopolitan species is widely distributed across both hemispheres, where it thrives in moist microhabitats. It favours moss-covered deciduous trees and rocks, often colonising over mosses and bryophytes. It occasionally grows on bare bark and on other lichens. Distinctive features of N. pulchella include its bluish-green squamules (scales) with sharply raised margins, non-reactivity to standard chemical spot tests, and growth in humid habitats.

Melaspilea is a genus of fungi in the family Melaspileaceae. The genus includes both lichen-forming species that grow on tree bark and lichenicolous species that parasitise other lichens. Originally, Melaspilea encompassed a broad and diverse group of species, but a 2015 molecular study narrowed its circumscription, showing that many species historically placed in the genus actually belonged to unrelated lineages. In its current sense, Melaspilea belongs to the family Melaspileaceae and order Eremithallales within Dothideomycetes and is characterised by dark fruiting bodies with single-septum

Lepraria lobificans is a species of leprose lichen in the family Stereocaulaceae. The species was first described in 1873 by the Finnish lichenologist William Nylander from specimens collected in France. It typically grows on bark, rock, and mossy substrates in shaded, humid forest environments. It is characterised by its cottony texture, weakly developed lobes, and chemical composition including atranorin and stictic acid. Molecular studies have since shown that Lepraria lobificans sensu stricto is genetically distinct from the closely related and more widespread L. finkii, with which it was

Lecanora gangaleoides is a species of crustose lichen in the family Lecanoraceae. It was described as new to science by William Nylander in 1872.

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Cladonia macrophyllodes, commonly known as the large-leaved cladonia or the large-leaved cup lichen, is a species of cup lichen in the family Cladoniaceae.

Spilonema revertens, the rock hairball lichen, is a species of fruticose lichen in the family Coccocarpiaceae. This dark-coloured cyanolichen forms small, dense cushions on rocks across the Northern Hemisphere. Found in Europe, Asia, North America, Macaronesia, and Greenland, it typically grows on exposed rocks that experience alternating wet and dry periods. The species is most commonly found in lower mountain zones, particularly in open coniferous forests and rocky steppes, though it also occurs in coastal areas. First described in 1865 from specimens collected in Finland, it is distinctive

Rimularia is a genus of lichen-forming fungi in the family Trapeliaceae. Established by the Finnish lichenologist William Nylander in 1868 from specimens collected on granitic rocks in France, the genus comprises 14 accepted species as of 2025. These rock-dwelling lichens form thin, crust-like growths that range from reddish-brown to dark olive-brown in colour and produce small black fruiting bodies with distinctive branched internal structures.

Ramalina intermedia, the rock ramalina, is a species of fruticose lichen in the family Ramalinaceae.

Pyxine petricola is a species of saxicolous (rock-dwelling), foliose lichen in the family Caliciaceae. The distribution of the lichen includes Australia, East Africa, North and Central America, and the Philippines.

Ptychographa is a fungal genus in the family Xylographaceae. It is a monospecific genus, containing the single species Ptychographa xylographoides. This inconspicuous lichen grows as a barely visible coating of dark grains on rotting logs and branches in undisturbed old forests. The species is most readily identified by its narrow, elongated black fruiting structures that run parallel to the wood grain.

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Peltula is a genus of small dark brown to olive or dark grey squamulose lichens. These lichens typically grow on rocks in arid and semi-arid environments worldwide. They consist of a fungus living in symbiosis with a photosynthetic partner, specifically a cyanobacterium of the genus Chroococcidiopsis. Peltula is the only genus in the family Peltulaceae, which belongs to the Lichinomycetes, a class of fungi that form lichens. The genus includes about 50 recognised species, which have a variety of growth forms ranging from flat and crust-like to more complex, leaf-like structures. Peltula

Normandina is a genus of lichen-forming fungi in the family Verrucariaceae. It has five species of crustose and squamulose (scaly) lichens.

The Myriangiaceae are a family of fungi in the Ascomycota, class Dothideomycetes. Species in this family have a widespread distribution (and are especially prevalent in tropical areas), and are typically found associated with scale insects. The family occupies an isolated phylogenetic position within the Dothideomycetes.