A herbarium (plural: herbaria ) is a collection of preserved plant specimens and associated data used for scientific study.
92-466: The specimens may be whole plants or plant parts; these will usually be in dried form mounted on a sheet of paper (called exsiccatum , plur. exsiccata ) but, depending upon the material, may also be stored in boxes or kept in alcohol or other preservative. The specimens in a herbarium are often used as reference material in describing plant taxa ; some specimens may be types , some may be specimens distributed in series called exsiccatae . The same term
184-436: A holobiont . Many lichens are very sensitive to environmental disturbances and can be used to cheaply assess air pollution , ozone depletion, and metal contamination. Lichens have been used in making dyes , perfumes ( oakmoss ), and in traditional medicines . A few lichen species are eaten by insects or larger animals, such as reindeer. Lichens are widely used as environmental indicators or bio-indicators. When air
276-621: A keystone species in many ecosystems and benefit trees and birds . The English word lichen derives from the Greek λειχήν leichēn ("tree moss, lichen, lichen-like eruption on skin") via Latin lichen . The Greek noun, which literally means "licker", derives from the verb λείχειν leichein , "to lick". In American English, "lichen" is pronounced the same as the verb "liken" ( / ˈ l aɪ k ən / ). In British English, both this pronunciation and one rhyming with "kitchen" ( / ˈ l ɪ tʃ ən / ) are used. Lichens grow in
368-406: A crustose lichen gets old, the center may start to crack up like old-dried paint, old-broken asphalt paving, or like the polygonal "islands" of cracked-up mud in a dried lakebed. This is called being rimose or areolate , and the "island" pieces separated by the cracks are called areolas. The areolas appear separated, but are (or were) connected by an underlying prothallus or hypothallus . When
460-413: A crustose lichen grows from a center and appears to radiate out, it is called crustose placodioid. When the edges of the areolas lift up from the substrate, it is called squamulose . These growth form groups are not precisely defined. Foliose lichens may sometimes branch and appear to be fruticose. Fruticose lichens may have flattened branching parts and appear leafy. Squamulose lichens may appear where
552-437: A few basic internal structure types. Common names for lichens often come from a growth form or color that is typical of a lichen genus . Common groupings of lichen thallus growth forms are: There are variations in growth types in a single lichen species, grey areas between the growth type descriptions, and overlapping between growth types, so some authors might describe lichens using different growth type descriptions. When
644-407: A foliose lichen may branch, giving the appearance of a fruticose lichen, but the underside will be a different color from the top side. The sheen on some jelly-like gelatinous lichens is created by mucilaginous secretions. A lichen consists of a simple photosynthesizing organism, usually a green alga or cyanobacterium , surrounded by filaments of a fungus. Generally, most of a lichen's bulk
736-488: A green algal or a cyanobacterial symbiont. Quite naturally, these alternative forms were at first considered to be different species, until they were found growing in a conjoined manner. Evidence that lichens are examples of successful symbiosis is the fact that lichens can be found in almost every habitat and geographic area on the planet. Two species in two genera of green algae are found in over 35% of all lichens, but can only rarely be found living on their own outside of
828-496: A herbarium can represent the only record of the plant's original distribution. Environmental scientists make use of such data to track changes in climate and human impact. Herbaria have also proven very useful as source of plant DNA for use in taxonomy and molecular systematics . Even ancient fungaria represent a source for DNA-barcoding of ancient samples. Many kinds of scientists and naturalists use herbaria to preserve voucher specimens; representative samples of plants used in
920-448: A host. Cyanobacteria in laboratory settings can grow faster when they are alone rather than when they are part of a lichen. Symbiosis in lichens is so well-balanced that lichens have been considered to be relatively self-contained miniature ecosystems in and of themselves. It is thought that lichens may be even more complex symbiotic systems that include non-photosynthetic bacterial communities performing other functions as partners in
1012-459: A lichen can survive outside the lichen, the lichen symbiotic association extends the ecological range of both partners, whereby most descriptions of lichen associations describe them as symbiotic. Both partners gain water and mineral nutrients mainly from the atmosphere, through rain and dust. The fungal partner protects the alga by retaining water, serving as a larger capture area for mineral nutrients and, in some cases, provides minerals obtained from
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#17328443352191104-519: A lichen. In a case where one fungal partner simultaneously had two green algae partners that outperform each other in different climates, this might indicate having more than one photosynthetic partner at the same time might enable the lichen to exist in a wider range of habitats and geographic locations. At least one form of lichen, the North American beard-like lichens, are constituted of not two but three symbiotic partners: an ascomycetous fungus,
1196-462: A millimeter). The cortex may be further topped by an epicortex of secretions, not cells, 0.6–1 μm thick in some lichens . This secretion layer may or may not have pores. Below the cortex layer is a layer called the photobiontic layer or symbiont layer . The symbiont layer has less densely packed fungal filaments, with the photosynthetic partner embedded in them. The less dense packing allows air circulation during photosynthesis, similar to
1288-579: A particular study to demonstrate precisely the source of their data, or to enable confirmation of identification at a future date. They may also be a repository of viable seeds for rare species. Many universities, museums, and botanical gardens maintain herbaria. Each is assigned an alphabetic code in the Index Herbariorum , between one and eight letters long. The largest herbaria in the world, in approximate order of decreasing size, are: Exsiccatum Exsiccata (Latin, gen. -ae, plur. -ae)
1380-440: A photosynthetic alga, and, unexpectedly, a basidiomycetous yeast. Phycobionts can have a net output of sugars with only water vapor. The thallus must be saturated with liquid water for cyanobionts to photosynthesize. Algae produce sugars that are absorbed by the fungus by diffusion into special fungal hyphae called appressoria or haustoria in contact with the wall of the algal cells. The appressoria or haustoria may produce
1472-428: A protective "skin" of densely packed fungal filaments, often containing a second fungal species, which is called a cortex. Fruticose lichens have one cortex layer wrapping around the "branches". Foliose lichens have an upper cortex on the top side of the "leaf", and a separate lower cortex on the bottom side. Crustose and squamulose lichens have only an upper cortex, with the "inside" of the lichen in direct contact with
1564-624: A result, most of the iDigBio web portals have a section for accessing specimens of exsiccatae, like the portal of the Consortium of Midwest Herbaria . Approaches to generate virtual herbaria are optimizing their label data capture with linking the specimen text information to standard abbreviations of the exsiccata series following (online) bibliographies and example label images for disambiguation purposes. Citizen science approaches for herbarium label digitization have instructions about how to recognize exsiccatae and how to mobilize this information in
1656-403: A single cortex wrapping all the way around the "stems" and "branches". The medulla is the lowest layer, and may form a cottony white inner core for the branchlike thallus, or it may be hollow. Crustose and squamulose lichens lack a lower cortex, and the medulla is in direct contact with the substrate that the lichen grows on. In crustose areolate lichens, the edges of the areolas peel up from
1748-429: A standard system of organizing their specimens into herbarium cases. Specimen sheets are stacked in groups by the species to which they belong and placed into a large lightweight folder that is labelled on the bottom edge. Groups of species folders are then placed together into larger, heavier folders by genus . The genus folders are then sorted by taxonomic family according to the standard system selected for use by
1840-571: A structured manner. An example is the guideline of the BGBM Herbonauten . . In general, the collections management systems used at major herbaria are able to handle data on exsiccata series and single exsiccata specimens. Similar as iDigBio the concept for complete digitization of German herbaria is including the mobilisation of this structured historical information using a standard reference list of editors, titles, abbreviations, publication dates and number ranges. This procedure will facilitate
1932-476: A substance that increases permeability of the algal cell walls, and may penetrate the walls. The algae may contribute up to 80% of their sugar production to the fungus. Lichen associations may be examples of mutualism or commensalism , but the lichen relationship can be considered parasitic under circumstances where the photosynthetic partner can exist in nature independently of the fungal partner, but not vice versa. Photobiont cells are routinely destroyed in
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#17328443352192024-764: A surface ( substrate ) like a thick coat of paint ( crustose ); have a powder-like appearance ( leprose ); or other growth forms . A macrolichen is a lichen that is either bush-like or leafy; all other lichens are termed microlichens . Here, "macro" and "micro" do not refer to size, but to the growth form. Common names for lichens may contain the word moss (e.g., " reindeer moss ", " Iceland moss "), and lichens may superficially look like and grow with mosses , but they are not closely related to mosses or any plant. Lichens do not have roots that absorb water and nutrients as plants do, but like plants, they produce their own nutrition by photosynthesis . When they grow on plants, they do not live as parasites , but instead use
2116-422: A wide range of shapes and forms; this external appearance is known as their morphology . The shape of a lichen is usually determined by the organization of the fungal filaments. The nonreproductive tissues, or vegetative body parts, are called the thallus . Lichens are grouped by thallus type, since the thallus is usually the most visually prominent part of the lichen. Thallus growth forms typically correspond to
2208-544: Is a known example. One of the well-known plant exchange organizations/ associations that existed more than a hundred years was the Société Française pour l'échange des plantes vasculaires , from 1911 to 2015. This organisation developed a large network of plant collectors worldwide, elaborated guidelines for plant collectors and distributed a number of exsiccata-like series, partly numbered, with printed labelsand distributed booklets. The last exsiccata-like series edited by
2300-442: Is a whitish coating on top of an upper surface. An epinecral layer is "a layer of horny dead fungal hyphae with indistinct lumina in or near the cortex above the algal layer". In August 2016, it was reported that some macrolichens have more than one species of fungus in their tissues. Lichens are fungi that have discovered agriculture A lichen is a composite organism that emerges from algae or cyanobacteria living among
2392-425: Is a work with "published, uniform, numbered set[s] of preserved specimens distributed with printed labels". Typically, exsiccatae are numbered collections of dried herbarium specimens or preserved biological samples published in several duplicate sets with a common theme or title, such as Lichenes Helvetici (see figure). Exsiccatae are regarded as scientific contributions of the editor(s) with characteristics from
2484-546: Is called the thallus . The thallus form is very different from any form where the fungus or alga are growing separately. The thallus is made up of filaments of the fungus called hyphae . The filaments grow by branching then rejoining to create a mesh, which is called being " anastomosed ". The mesh of fungal filaments may be dense or loose. Generally, the fungal mesh surrounds the algal or cyanobacterial cells, often enclosing them within complex fungal tissues that are unique to lichen associations. The thallus may or may not have
2576-450: Is especially rich in the earlier collections made in the eighteenth and early nineteenth centuries, contains the types of many species founded by the earlier workers in botany . It is also rich in types of Australian plants from the collections of Sir Joseph Banks and Robert Brown , and contains in addition many valuable modern collections. The large herbaria have many exsiccata series included in their collections. Most herbaria utilize
2668-456: Is for the education of physician, pharmacists and teachers. With this goal, the system of exsiccatae is originated from herbarium books with images of plants and fungi, such as the Herbaria viva distributed in the 16th and 17th century, but now contained dried and pressed plant material. Series with scholarly and scientific focus followed few years later. One of that kind of series was published by
2760-400: Is made of interwoven fungal filaments, but this is reversed in filamentous and gelatinous lichens. The fungus is called a mycobiont . The photosynthesizing organism is called a photobiont . Algal photobionts are called phycobionts . Cyanobacteria photobionts are called cyanobionts . The part of a lichen that is not involved in reproduction, the "body" or "vegetative tissue" of a lichen,
2852-449: Is missing. The IndExs – Index of Exsiccatae online database closes the gap. Exsiccatae are also known under the terms exsiccatal series, exsiccata(e) series, exsiccata(e) works, exsiccatae collections, sometimes exsiccati, exsiccate. Furthermore, the feminine noun term "exsiccata" (Latin, gen. -ae, plur. -ae) for exsiccata series is often not clearly distinguished from the neuter noun "exsiccatum" (Latin, gen. -i, plur. -a) which
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2944-549: Is often used in mycology to describe an equivalent collection of preserved fungi , otherwise known as a fungarium . A xylarium is a herbarium specialising in specimens of wood. The term hortorium (as in the Liberty Hyde Bailey Hortorium ) has occasionally been applied to a herbarium specialising in preserving material of horticultural origin. The techniques for making herbaria have changed little over at least six centuries. They have been an important step in
3036-653: Is published and distributed is often unknown. In large institutional herbaria (see List of herbaria ), the exsiccatae are often not kept in their original sets, but each single numbered specimen unit is inserted in the general collections and filed under the current taxon name, e.g. in M and in HUH (FH). In the 19th century with mid of 20th century, exsiccatae played an important role in botany, mycology and binomial nomenclature . A lot of taxa were described with diagnosis in exsiccatae or exsiccatal-like specimen series using printed labels and schedae booklets for effective publication of
3128-478: Is the Société Rochelaise pour l'échange des plantes françaises , starting in 1880, with around 15 specimen series. In addition to the plant exchange organisations described above, there were learned societies which, among other activities, published and distributed exsiccata-like collections of specimens. The Broterian Society with Flora Lusitanica (Soc. Brot. 1. anno) and its annual follow-up collections
3220-490: Is the early Unio Itineraria , a society, which financially supported the scientific voyages of Georg Wilhelm Schimper and distributed series with printed labels like Schimper, Unio Itineraria 1835 , and others. There were also individuals starting as plant collectors and later switching on dealing with exsiccata-like series. A famous example is Ignaz Dörfler who earned a living with this kind of trade for more than twenty years from 1894 until 1915. Some modern definitions of
3312-559: Is used in general for a dried herbarium specimen. There exists also the Latin adjective "exsiccatus, -a, -um" meaning "dried" which is often part of a Latin title of an exsiccata, e.g. Lichenes exsiccati . The oldest series known as an exsiccata is that of the German naturalist and pharmacist Johann Balthasar Ehrhart [ de ] called Herbarium vivum recens collectum... It was distributed in 1732. The plant material and text information
3404-452: Is usually determined by the photosynthetic component. Special pigments, such as yellow usnic acid , give lichens a variety of colors, including reds, oranges, yellows, and browns, especially in exposed, dry habitats. In the absence of special pigments, lichens are usually bright green to olive gray when wet, gray or grayish-green to brown when dry. This is because moisture causes the surface skin ( cortex ) to become more transparent, exposing
3496-403: Is very badly polluted with sulphur dioxide, there may be no lichens present; only some green algae can tolerate those conditions. If the air is clean, then shrubby, hairy and leafy lichens become abundant. A few lichen species can tolerate fairly high levels of pollution, and are commonly found in urban areas, on pavements, walls and tree bark. The most sensitive lichens are shrubby and leafy, while
3588-483: The hortus siccus (1566) of Petrus Cadé. While most of the early herbaria were prepared with sheets bound into books, Carl Linnaeus came up with the idea of maintaining them on free sheets that allowed their easy re-ordering within cabinets. Commensurate with the need to identify the specimen, it is essential to include in a herbarium sheet as much of the plant as possible (e.g., roots, flowers, stems, leaves, seed, and fruit), or at least representative parts of them in
3680-590: The Fungi Rhenani of Karl Wilhelm Gottlieb Leopold Fuckel , many taxonomic type specimens are among the 2,700 numbered specimen units, now labelled as isotypes or lectotypes . In 2001, a web portal with underlying database called IndExs – Index of Exsiccatae was published with the goal of gathering and providing bibliographic information on all types of exsiccatae and exsiccata-like series. Currently more than 2,200 series with more than 1,300 editors are known. The editors are often well known as taxonomists . In
3772-448: The Société pour l'Échange des Plantes vasculaires de l'Europe et du Bassin méditerranéen et correspondant finally distributed 20,000 specimen units of vascular plants and started in 1947. The last secretary and in this function editor of the series was Jacques Lambinon [ fr ] . Few organizations had business models for selling exsiccatae and exsiccatae-like series. An example
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3864-436: The apoplast . Secondary metabolites are thought to play a role in preference for some substrates over others. Lichens often have a regular but very slow growth rate of less than a millimeter per year. In crustose lichens, the area along the margin is where the most active growth is taking place. Most crustose lichens grow only 1–2 mm in diameter per year. Lichens may be long-lived , with some considered to be among
3956-542: The flora of an area. A large collection from a single area is used in writing a field guide or manual to aid in the identification of plants that grow there. With more specimens available, the author or the guide will better understand the variability of form in the plants and the natural distribution over which the plants grow. Herbaria also preserve a historical record of change in vegetation over time. In some cases, plants become extinct in one area or may become extinct altogether. In such cases, specimens preserved in
4048-404: The library world (published booklets of scientific literature , with authors/ editors , titles, often published in serial publications like journals and magazines and in serial formats with fascicles ) and features from the herbarium world (uniform and numbered collections of duplicate herbarium specimens). Exsiccatae works represent a special method of scholarly communication . The text in
4140-416: The substrate . If a cyanobacterium is present, as a primary partner or another symbiont in addition to a green alga as in certain tripartite lichens, they can fix atmospheric nitrogen , complementing the activities of the green alga. In three different lineages the fungal partner has independently lost the mitochondrial gene atp9, which has key functions in mitochondrial energy production. The loss makes
4232-524: The 19th century a number of exsiccata-like series and duplicate specimen collections which superficially resemble exsiccatae are known: Some are without descriptive titles (instead they may have an organization as header), some without mentioned editors, others with labels that are in parts handwritten with handwritten numbers, and series without sequential numbers as well as series whose sets are not uniform and schedae which are not published as independent schedae work. Some works as that of William Gardiner with
4324-496: The 2,300 known exsiccatae appeared in the 19th century. They are often specialised by a single organism group or geographical region. Two examples: Alexander Braun , Gottlob Ludwig Rabenhorst and Ernst Stizenberger have distributed Die Characeen Europa's in getrockneten Exemplaren, unter Mitwirkung mehrerer Freunde der Botanik, gesammelt und herausgegeben von Prof. A. Braun, L. Rabenhorst und E. Stizenberger in 1878 and Thomas Drummond published Musci Americani; or, specimens of
4416-410: The 350 million botanical specimens in the major herbaria belong to the 2,200 widely distributed exsiccatae and exsiccata-like series. The specimens are either included in the general collections of the major herbaria or kept there as separate fascicles (see Index Herbariorum ). Thus, the series are explicitly addressed by joint advanced digitization projects of biodiversity collections like iDigBio . As
4508-544: The Stockholm Code) the printed matters accompanying exsiccatae must be distributed independently of the exsiccatae for effective publication (see, e.g., Vienna Code 2006, Article 30.4). The recent code (Shenzhen Code 2018) does only mention exsiccatae explicitly but gives two exsiccatae as examples for effective publication under Article 30.8, Note 2. This correlates with the minor role that current exsiccatae play today with around 70 series running. Approximately 10 million of
4600-642: The Swiss botanist Jakob Friedrich Ehrhart , a pupil of Carl Linnaeus , with the title Plantae cryptogamae Linn., quas in locis earum natalibus collegit et exsiccavit Fridericus Ehrhart . The first fascicle was delivered in 1785. As one of the first Jakob Friedrich Ehrhart promoted the selling of dried plants with several series, among others Arbores, frutices et suffrutices Linnaei quas in usum dendrophilorum collegit et exsiccavit Fr. Ehrhart and Calamariae, Gramina et Tripetaloideae Linnaei, quas in usum botanicophilorum collegit et exsiccavit Fr. Ehrhart . The majority of
4692-420: The anatomy of a leaf. Each cell or group of cells of the photobiont is usually individually wrapped by hyphae, and in some cases penetrated by a haustorium . In crustose and foliose lichens, algae in the photobiontic layer are diffuse among the fungal filaments, decreasing in gradation into the layer below. In fruticose lichens, the photobiontic layer is sharply distinct from the layer below. The layer beneath
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#17328443352194784-405: The case of large specimens. To preserve their form and colour, plants collected in the field are carefully arranged and spread flat between thin sheets, known as flimsies (equivalent to sheets of newsprint), and dried, usually in a plant press , between blotters or absorbent paper. During the drying process the specimens are retained within their flimsies at all times to minimize damage, and only
4876-465: The case that they published exsiccatae, the series are explicitly cited in Frans Stafleu and Richard Sumner Cowan 's standard work Taxonomic Literature: A Selective Guide to Botanical Publications and Collections, with Dates, Commentaries, and Types (7 volumes) and in the 8 volumes of the supplement series with the first 6 co-authored by Erik Albert Mennega . How many issues (= sets) of an exsiccata
4968-445: The characteristic cortex of the lichen thallus, and could also be important for its shape. The lichen combination of alga or cyanobacterium with a fungus has a very different form (morphology), physiology, and biochemistry than the component fungus, alga, or cyanobacterium growing by itself, naturally or in culture. The body ( thallus ) of most lichens is different from those of either the fungus or alga growing separately. When grown in
5060-673: The cortex or "skin", in a mutualistic relationship. Lichens are the lifeform that first brought the term symbiosis (as symbiotismus ) under biological context. Lichens have since been recognized as important actors in nutrient cycling and producers which many higher trophic feeders feed on, such as reindeer, gastropods, nematodes, mites, and springtails. Lichens have properties different from those of their component organisms. They come in many colors, sizes, and forms and are sometimes plant-like, but are not plants . They may have tiny, leafless branches ( fruticose ); flat leaf-like structures ( foliose ); grow crust-like, adhering tightly to
5152-435: The course of nutrient exchange. The association continues because reproduction of the photobiont cells matches the rate at which they are destroyed. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations. In many species the fungus penetrates the algal cell wall, forming penetration pegs ( haustoria ) similar to those produced by pathogenic fungi that feed on
5244-476: The discovery of duplicate exsiccata specimens in the various herbaria and avoid multiple typing of the same text information. The mobilisation of this data is regarded as an example for creating synergies between institutional herbaria during the digitization process. Ideally, exsiccatae comprise dried plant or fungus material as a result of plant collecting , have a descriptive title, one or more editors (or alternatively an editing organisation), printed labels and
5336-640: The edges lift up. Gelatinous lichens may appear leafy when dry. The thallus is not always the part of the lichen that is most visually noticeable. Some lichens can grow inside solid rock between the grains ( endolithic lichens ), with only the sexual fruiting part visible growing outside the rock. These may be dramatic in color or appearance. Forms of these sexual parts are not in the above growth form categories. The most visually noticeable reproductive parts are often circular, raised, plate-like or disc-like outgrowths, with crinkly edges, and are described in sections below. Lichens come in many colors. Coloration
5428-441: The filaments ( hyphae ) of the fungi in a mutually beneficial symbiotic relationship. The fungi benefit from the carbohydrates produced by the algae or cyanobacteria via photosynthesis . The algae or cyanobacteria benefit by being protected from the environment by the filaments of the fungi, which also gather moisture and nutrients from the environment, and (usually) provide an anchor to it. Although some photosynthetic partners in
5520-421: The fungi completely dependent on their symbionts. The algal or cyanobacterial cells are photosynthetic and, as in plants, they reduce atmospheric carbon dioxide into organic carbon sugars to feed both symbionts. Phycobionts (algae) produce sugar alcohols ( ribitol , sorbitol , and erythritol ), which are absorbed by the mycobiont (fungus). Cyanobionts produce glucose . Lichenized fungal cells can make
5612-501: The fungi, algae, or cyanobacteria have the potential to engage with other microorganisms in a functioning system that may evolve as an even more complex composite organism . Lichens may be long-lived , with some considered to be among the oldest living things. They are among the first living things to grow on fresh rock exposed after an event such as a landslide. The long life-span and slow and regular growth rate of some species can be used to date events ( lichenometry ). Lichens are
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#17328443352195704-460: The fungus living inside the lichen; thus they are not considered to be part of the lichen. Moisture makes the cortex become more transparent. This way, the algae can conduct photosynthesis when moisture is available, and is protected at other times. When the cortex is more transparent, the algae show more clearly and the lichen looks greener. Lichens can show intense antioxidant activity. Secondary metabolites are often deposited as crystals in
5796-472: The green photobiont layer. Different colored lichens covering large areas of exposed rock surfaces, or lichens covering or hanging from bark can be a spectacular display when the patches of diverse colors "come to life" or "glow" in brilliant displays following rain. Different colored lichens may inhabit different adjacent sections of a rock face, depending on the angle of exposure to light. Colonies of lichens may be spectacular in appearance, dominating much of
5888-483: The herbarium and placed into pigeonholes in herbarium cabinets. Locating a specimen filed in the herbarium requires knowing the nomenclature and classification used by the herbarium. It also requires familiarity with possible name changes that have occurred since the specimen was collected, since the specimen may be filed under an older name. Herbarium collections can have great significance and value to science, and have many uses. Herbaria have long been essential for
5980-567: The increase of the trade and the exchange with plant material: More than 100 societies for plant exchange purposes, mostly with non-commercial goals were founded, so-called plant exchange organizations , which build networks of citizen science to exchange plant material among their individual, private members. They were busy announcing new material, e.g., in scientific journals like Flora (Regensburg) . Some of them distributed specimen series with characteristic printed labels superficially resembling exsiccatae, mostly with anonymous editors. An example
6072-441: The laboratory in the absence of its photobiont, a lichen fungus develops as a structureless, undifferentiated mass of fungal filaments ( hyphae ). If combined with its photobiont under appropriate conditions, its characteristic form associated with the photobiont emerges, in the process called morphogenesis . In a few remarkable cases, a single lichen fungus can develop into two very different lichen forms when associating with either
6164-409: The lichen contacts the environment, is called a cortex . The cortex is made of densely tightly woven, packed, and glued together ( agglutinated ) fungal filaments. The dense packing makes the cortex act like a protective "skin", keeping other organisms out, and reducing the intensity of sunlight on the layers below. The cortex layer can be up to several hundred micrometers (μm) in thickness (less than
6256-458: The method of preservation, detailed information on where and when the plant and fungus was collected, habitat, color (since it may fade over time), and the name of the collector is usually included. The value of a herbarium is much enhanced by the possession of types , that is, the original specimens on which the study of a species was founded. Thus the herbarium at the British Museum , which
6348-957: The mosses collected in British North America, and chiefly among the Rocky Mountains, during the Second Land Arctic Expedition under the command of Captain Franklin, R.N. by Thomas Drummond, Assistant Naturalist ... in 1828. Some series are devoted to organisms of economical or medicinal relevance, and thus of interest for pharmacists, plant pathologists, veterinarians, people working in horticulture, agriculture and forestry. Felix von Thümen published some exsiccatal series of this kind, e.g., Herbarium mycologicum oeconomicum . Exsiccatae are well-known reference systems in collection-based life science and biodiversity research. Especially in early, large and widely distributed series like
6440-420: The most tolerant lichens are all crusty in appearance. Since industrialisation, many of the shrubby and leafy lichens such as Ramalina , Usnea and Lobaria species have very limited ranges, often being confined to the areas which have the cleanest air. Some fungi can only be found living on lichens as obligate parasites . These are referred to as lichenicolous fungi , and are a different species from
6532-546: The names, see for example Iris camillae described by Alexander Alfonsovich Grossheim in the schedae of Plantae orientales exsiccatae . These printed matters are often so-called grey literature . In the Vienna rules (1906) of the ICBN, now International Code of Nomenclature for algae, fungi, and plants (ICN), exsiccatae and their printed matters were explicitly mentioned in the context of valid publication (Article 37). With 1953 (under
6624-539: The oldest living organisms. Lifespan is difficult to measure because what defines the "same" individual lichen is not precise. Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the "same" lichen, and two lichens can merge, then becoming the "same" lichen. One specimen of Rhizocarpon geographicum on East Baffin Island has an estimated age of 9500 years. Thalli of Rhizocarpon geographicum and Rhizocarpon eupetraeoides / inarense in
6716-414: The photobiont "leak" out the products of photosynthesis, where they can then be absorbed by the fungus. It appears many, probably the majority, of lichen also live in a symbiotic relationship with an order of basidiomycete yeasts called Cyphobasidiales . The absence of this third partner could explain why growing lichen in the laboratory is difficult. The yeast cells are responsible for the formation of
6808-434: The photosynthetic partner tend to be dark grey, brown, or black. The underside of the leaf-like lobes of foliose lichens is a different color from the top side ( dorsiventral ), often brown or black, sometimes white. A fruticose lichen may have flattened "branches", appearing similar to a foliose lichen, but the underside of a leaf-like structure on a fruticose lichen is the same color as the top side. The leaf-like lobes of
6900-442: The plant's surface as a substrate. Lichens occur from sea level to high alpine elevations, in many environmental conditions, and can grow on almost any surface. They are abundant growing on bark, leaves , mosses, or other lichens and hanging from branches "living on thin air" ( epiphytes ) in rainforests and in temperate woodland . They grow on rock, walls, gravestones , roofs , exposed soil surfaces, rubber, bones, and in
6992-750: The plant, altitude, and special habitat conditions. The sheet is then placed in a protective case. As a precaution against insect attack, the pressed plant is frozen or poisoned, and the case disinfected. Certain groups of plants and fungi are soft, bulky, or otherwise not amenable to drying and mounting on sheets. For these plants, other methods of preparation and storage may be used. For example, conifer cones and palm fronds may be stored in labelled boxes. Representative flowers or fruits may be pickled in formaldehyde to preserve their three-dimensional structure. Small specimens, such as saprophytic and plant parasitic microfungi , mosses and lichens , are often air-dried and packaged in small paper envelopes. No matter
7084-409: The printed matters/published booklets is basically a list of labels ( schedae [ de ] ) with information on each single numbered exsiccatal unit. Extensions of the concept occur. There are several comprehensive bibliographies and treatments on exsiccatae devoted to algae , bryophytes and lichens, lichens and fungi . A printed bibliography on works devoted to vascular plants
7176-420: The sale of exsiccatae and exsiccata-like series in a professional manner. Some individual historical collections of mounted plants ( herbaria ) were bounded as splendid book volumes. This kind of unique herbaria might superficially resemble exsiccatae and were offered for purchase to single academic societies and princely courts as for example Giorgio Jan did at the beginning of the 19th century. In few cases
7268-700: The single dried specimens have printed taxon names, locality information and exsiccatal numbers and are distributed in sets/fascicles. The publication size vary depending on the work from very few until up to 70 duplicate specimens per numbered unit. Over time, with the changing goals in the wide field of organismic botany and mycology there were deviations in all aspects. There are exsiccata-like series distributing preserved natural objects other than dried herbarium material. Examples are glass slides with microorganisms, see Diatomacearum species typicae edited by Hamilton Lanphere Smith , and slides of wood, see American Woods edited by Romeyn Beck Hough . Especially within
7360-506: The soil as part of biological soil crusts . Various lichens have adapted to survive in some of the most extreme environments on Earth: arctic tundra , hot dry deserts , rocky coasts , and toxic slag heaps. They can even live inside solid rock, growing between the grains ( endolithic ). There are about 20,000 known species. Some lichens have lost the ability to reproduce sexually, yet continue to speciate . They can be seen as being relatively self-contained miniature ecosystems , where
7452-666: The study of plant taxonomy , the study of geographic distributions, and the stabilizing of nomenclature. Most of Carl Linnaeus 's collections are housed at the Linnaean Herbarium , which contains over 4,000 types and now belongs to the Linnean Society in England. Modern scientists continue to develop novel, non-traditional uses for herbarium specimens that extend beyond what the original collectors could have anticipated. Specimens housed in herbaria may be used to catalogue or identify
7544-412: The substrate and appear leafy. In squamulose lichens the part of the lichen thallus that is not attached to the substrate may also appear leafy. But these leafy parts lack a lower cortex, which distinguishes crustose and squamulose lichens from foliose lichens. Conversely, foliose lichens may appear flattened against the substrate like a crustose lichen, but most of the leaf-like lobes can be lifted up from
7636-438: The substrate because it is separated from it by a tightly packed lower cortex. Gelatinous, byssoid, and leprose lichens lack a cortex (are ecorticate ), and generally have only undifferentiated tissue, similar to only having a symbiont layer. In lichens that include both green algal and cyanobacterial symbionts, the cyanobacteria may be held on the upper or lower surface in small pustules called cephalodia . Pruinia
7728-410: The surface of the visual landscape in forests and natural places, such as the vertical "paint" covering the vast rock faces of Yosemite National Park . Color is used in identification. The color of a lichen changes depending on whether the lichen is wet or dry. Color descriptions used for identification are based on the color that shows when the lichen is dry. Dry lichens with a cyanobacterium as
7820-492: The surface they grow on (the substrate ). Even if the edges peel up from the substrate and appear flat and leaf-like, they lack a lower cortex, unlike foliose lichens. Filamentous, byssoid, leprose, gelatinous, and other lichens do not have a cortex; in other words, they are ecorticate . Fruticose, foliose, crustose, and squamulose lichens generally have up to three different types of tissue, differentiated by having different densities of fungal filaments. The top layer, where
7912-472: The symbiont layer is called the medulla . The medulla is less densely packed with fungal filaments than the layers above. In foliose lichens, as in Peltigera , there is usually another densely packed layer of fungal filaments called the lower cortex. Root-like fungal structures called rhizines ( usually ) grow from the lower cortex to attach or anchor the lichen to the substrate. Fruticose lichens have
8004-498: The term exsiccata is used for characterizing botanical art works bounded as books, which contain decorative assortments of pressed plant specimens mounted to the pages, usually arranged in a theme. Lichen A lichen ( / ˈ l aɪ k ən / LY -kən , UK also / ˈ l ɪ tʃ ən / LITCH -ən ) is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungi species, along with yeasts and bacteria embedded in
8096-501: The term exsiccata reflect the purpose of sale and subscription in delivering exsiccatae, e.g. that in A Grammatical Dictionary of Botanical Latin . The recipients and buyers were private plant collectors, as well as learned societies and institutional herbaria. For more than two decades (1908-1932) there existed the journal Herbarium. Organ zur Förderung des Austausches wissenschaftlicher Exsiccatensammlungen Band I + II, no. 1-86 published by Theodor Oswald Weigel, Leipzig, who organised
8188-528: The thicker, absorbent drying sheets are replaced. For some plants it may prove helpful to allow the fresh specimen to wilt slightly before being arranged for the press. An opportunity to check, rearrange and further lay out the specimen to best reveal the required features of the plant occurs when the damp absorbent sheets are changed during the drying/pressing process. The specimens, which are then mounted on sheets of stiff white paper, are labelled with all essential data, such as date and place found, description of
8280-411: The title Twenty lessons on British Mosses; first steps to a knowledge of that beautiful tribe of plants ... illustrated with specimens with mounted herbarium specimens are primarily for educational purposes. This is also the case with the series Educational collections of Australian plants , edited by Ferdinand von Mueller . These works are regularly treated as library objects. The 19th century saw
8372-794: The transformation of the study of plants from a branch of medicine to an independent discipline, and to make available plant material from far away places and over a long period of time. The oldest traditions of making herbarium collections have been traced to Italy. The Bologna physician and botanist, Luca Ghini (1490–1556) reintroduced the study of actual plants as opposed to relying on classical texts, such as Dioscorides , which lacked sufficient accuracy for identification. At first, he needed to make available plant material, even in winter, hence his Hortus hiemalis (winter garden) or Hortus siccus (dry garden). He and his students placed freshly gathered plants between two sheets of paper and applied pressure to flatten them and absorb moisture. The dried specimen
8464-562: Was then glued onto a page in a book and annotated. This practice was supplemented by the parallel development of the Hortus simplicium or Orto botanico ( botanical garden ) to supply material, which he established at the University of Pisa in 1544. Although Ghini's herbarium has not survived, the oldest extant herbarium is that of Gherardo Cibo from around 1532. and in the Lower Countries
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