Usnea is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs. The genus is in the family Parmeliaceae. It grows all over the world. Members of the genus are commonly called old man's beard, beard lichen, or beard moss.
Irwin M. Brodo is an emeritus scientist at the Canadian Museum of Nature, in Ottawa, Ontario, Canada. He is an authority on the identification and biology of lichens. Irwin Brodo was honored in 1994 with an Acharius Medal presented to him by the International Association for Lichenology.
Verrucariaceae is a family of lichens and a few non-lichenised fungi in the order Verrucariales. The lichens have a wide variety of thallus forms, from crustose (crust-like) to foliose (bushy) and squamulose (scaly). Most of them grow on land, some in freshwater and a few in the sea. Many are free-living but there are some species that are parasites on other lichens, while one marine species always lives together with a leafy green alga.
Caloplaca is a lichen genus comprising a number of distinct species. Members of the genus are commonly called firedot lichen, jewel lichen. gold lichens, "orange lichens", but they are not always orange, as in the case of C. albovariegata. The distribution of this lichen genus is worldwide, extending from Antarctica to the high Arctic. It includes a portion of northern North America and the Russian High Arctic. There are about thirty species of Caloplaca in the flora of the British Isles. An example species in this genus is Caloplaca saxicola, a lichen with worldwide distribution including the Antarctic continent, Europe and northern North America including the northern reaches of the Canadian boreal forests.
Pseudocyphellaria is a genus of large, leafy lichens that are sometimes referred to as "specklebelly" lichens. The genus has a widespread distribution, especially in south temperate regions, and contains about 170 species. They resemble Lobaria, except that most species of Pseudocyphellaria have conspicuous pseudocyphellae on their lower surface, a characteristic that was once considered unique to this genus. Some species contain pulvinic acid-related pigments; in these species the soredia and pseudocyphellae can be bright yellow.
Nephroma is a genus of medium to large foliose lichens. The genus has a widespread distribution. They are sometimes called kidney lichens, named after the characteristic kidney-shaped apothecia that they produce on the lower surface of their lobe tips, which often curl upwards and thus are visible from above. Sterile specimens that do not have apothecia can look somewhat like Melanelia, Peltigera, Platismatia, or Asahinea. Most species grow either on mossy ground or rocks, or on trees.
Icmadophila is a genus of crustose lichen. The genus has a widespread distribution in the Northern Hemisphere and contains six species. The only species found in North America, Icmadophila ericetorum, has a mint green crustose thallus that is dotted with bright pink apothecial disks, and is sometimes colloquially referred to as "fairy puke". It aggressively grows over mosses on well-rotted wood and peat. It looks very distinctive, but may be confused with species of Dibaeis.
Niebla is a genus of yellow-green fruticose lichens that grow on rocks, trees, and shrubs within the fog zone of coastal North America, or more narrowly defined to occur on rocks and soil along the Pacific Coast from Mendocino County in California south to Baja California Sur.
Pseudocyphellae are structures in lichens that appear as tiny pores on the outer surface (the cortex of the lichen. They are caused when there is a break in the cortex of the lichen, and the medullary hyphae extend to the surface. Pseudocyphellae are the same colour as the medulla of the lichen, which is generally white, but can be yellow in some species of Pseudocyphellaria and in Bryoria fremontii. The presence/absence, abundance, colour, and shape of pseudocyphellae can all be diagnostic features used to identify different species. They facilitate gas exchange through the surface of the lichen, and may provide an adaptive advantage in temperate environments.
Chrysothrix is a genus of lichen-forming fungi in the family Chrysothricaceae. They are commonly called gold dust lichens or sulfur dust lichens, because they are bright yellow to greenish-yellow, sometimes flecked with orange, and composed entirely of powdery soredia. Apothecia are never present in North American specimens.
A lichenicolous fungus is a parasitic fungus that only lives on lichen as the host. A lichenicolous fungus is not the same as the fungus that is the component of the lichen, which is known as a lichenized fungus. They are most commonly specific to a given fungus as the host, but they also include a wide range of pathogens, saprotrophs, and commensals. It is estimated there are 3000 species of lichenicolous fungi. More than 1800 species are already described among the Ascomycota and Basidiomycota. More than 95% of lichenicolous fungi described as of 2003 are ascomycetes, in 7 classes and 19 orders. Although basidiomycetes have less than 5% of lichenicolous lichen species, they represent 4 classes and 8 orders. Many lichenicolous species have yet to be assigned a phylogenetic position as of 2003.
Lichens are symbiotic organisms made up of multiple species: a fungus, one or more photobionts and sometimes a yeast. They are regularly grouped by their external appearance – a characteristic known as their growth form. This form, which is based on the appearance of vegetative part of the lichen, varies depending on the species and the environmental conditions it faces. Those who study lichens (lichenologists) have described a dozen of these forms: areolate, byssoid, calicioid, cladoniform, crustose, filamentous, foliose, fruticose, gelatinous, leprose, placoidioid and squamulose. Traditionally, crustose (flat), foliose (leafy) and fruticose (shrubby) are considered to be the three main forms. In addition to these more formalised, traditional growth types, there are a handful of informal types named for their resemblance to the lichens of specific genera. These include alectorioid, catapyrenioid, cetrarioid, hypogymnioid, parmelioid and usneoid.
Dermatocarpon americanum is a silvery-gray, leafy (foliose) lichen with black dots that is common on near seeps in rock faces from southwestern North American deserts to coastal areas. It has a silvery-dusty looking coating. It is common in deserts on vertical rock surfaces that are partially shade protected near seepages.
Niebla homalea is a species of fruticose lichen that grows on rocks in foggy areas along the Pacific Coast of North America, from Mendocino County, California south to Bahía de San Quintín on the main peninsula of Baja California, with an isolated occurrence further south on vertical rock faces above Punta Camachos, and other occurrences in the Channel Islands and on Guadalupe Island. The epithet homalea, given by Acharius, suggests it was in regard to the branches appearing flattened.
Pyxine sorediata, commonly known as mustard lichen, is a widely distributed species of foliose lichen in the family Caliciaceae. It has a subtropical to warm temperate distribution, and grows on bark, rocks, and moss as substrates. Pyxine sorediata has been reported from regions of North America, Europe, Africa, Asia, and Australasia.
Cladonia cervicornis is a species of cup lichen in the family Cladoniaceae. It was first described by Swedish lichenologist Erik Acharius in 1799 as Lichen cervicornis. Julius von Flotow transferred it to the genus Cladonia in 1849. In North America, it is colloquially known as the ladder lichen or elk's-horn cup lichen.
Ephebe lanata is a species of filamentous lichen in the family Lichinaceae, and the type species of the genus Ephebe. The lichen was first described as a new species by Swedish taxonomist Carl Linnaeus in his seminal 1753 work Species Plantarum, as Lichen lanatus. Finnish lichenologist Edvard August Vainio transferred it to Ephebe in 1888. In North America, it is known colloquially as the "rockshag lichen".
Placidium arboreum, commonly known as the tree stipplescale, is a species of corticolous (bark-dwelling), squamulose (scaley) lichen in the family Verrucariaceae. It has a primarily North American distribution, with a range extending from eastern Canada south to Mexico, although it has also been reported from the West Indies and from Argentina.
The following outline provides an overview of and topical guide to lichens.
Dermatocarpon tomentulosum is a species of lichen belonging to the family Verrucariaceae. A rare species, it is known only to a few localities in North America—Missouri and Texas in the United States, and Cat Island and New Providence in the Bahamas.
