Order ( Latin : ordo ) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy . It is classified between family and class . In biological classification , the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes . An immediately higher rank, superorder , is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families.
63-460: See text Veneroida Venerida (formerly Veneroida ) is an order of mostly saltwater but also some freshwater bivalve molluscs . This order includes many familiar groups such as many clams that are valued for food and a number of freshwater bivalves . Since the 2000s, the taxonomy currently represented in the World Register of Marine Species (WoRMS) classifies several taxa contained in
126-585: A bend in the middle that is caused by start of the twin. Penetration twins consist of two single crystals that have grown into each other; examples of this twinning include cross-shaped staurolite twins and Carlsbad twinning in orthoclase. Cyclic twins are caused by repeated twinning around a rotation axis. This type of twinning occurs around three, four, five, six, or eight-fold axes, and the corresponding patterns are called threelings, fourlings, fivelings , sixlings, and eightlings. Sixlings are common in aragonite. Polysynthetic twins are similar to cyclic twins through
189-417: A bigger coordination numbers because of the increase in relative size as compared to oxygen (the last orbital subshell of heavier atoms is different too). Changes in coordination numbers leads to physical and mineralogical differences; for example, at high pressure, such as in the mantle , many minerals, especially silicates such as olivine and garnet , will change to a perovskite structure , where silicon
252-429: A characteristic folded gill structure adapted to that way of life. In 2002, Gonzalo Giribet and Ward Wheeler suggested that the orders Myoida and Veneroida were not monophyletic. They have since been widely reorganised. Order: Venerida Order (biology) What does and does not belong to each order is determined by a taxonomist , as is whether a particular order should be recognized at all. Often there
315-416: A definite crystalline structure, such as opal or obsidian , are more properly called mineraloids . If a chemical compound occurs naturally with different crystal structures, each structure is considered a different mineral species. Thus, for example, quartz and stishovite are two different minerals consisting of the same compound, silicon dioxide . The International Mineralogical Association (IMA)
378-470: A distinct mineral: The details of these rules are somewhat controversial. For instance, there have been several recent proposals to classify amorphous substances as minerals, but they have not been accepted by the IMA. The IMA is also reluctant to accept minerals that occur naturally only in the form of nanoparticles a few hundred atoms across, but has not defined a minimum crystal size. Some authors require
441-463: A key to defining a substance as a mineral. A 2011 article defined icosahedrite , an aluminium-iron-copper alloy, as a mineral; named for its unique natural icosahedral symmetry , it is a quasicrystal . Unlike a true crystal, quasicrystals are ordered but not periodic. A rock is an aggregate of one or more minerals or mineraloids. Some rocks, such as limestone or quartzite , are composed primarily of one mineral – calcite or aragonite in
504-409: A mineral defines how much it can resist scratching or indentation. This physical property is controlled by the chemical composition and crystalline structure of a mineral. The most commonly used scale of measurement is the ordinal Mohs hardness scale, which measures resistance to scratching. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc,
567-432: A sedimentary mineral, and silicic acid ): Under low-grade metamorphic conditions, kaolinite reacts with quartz to form pyrophyllite (Al 2 Si 4 O 10 (OH) 2 ): As metamorphic grade increases, the pyrophyllite reacts to form kyanite and quartz: Alternatively, a mineral may change its crystal structure as a consequence of changes in temperature and pressure without reacting. For example, quartz will change into
630-406: A tetrahedral fashion; on the other hand, graphite is composed of sheets of carbons in sp hybrid orbitals, where each carbon is bonded covalently to only three others. These sheets are held together by much weaker van der Waals forces , and this discrepancy translates to large macroscopic differences. Twinning is the intergrowth of two or more crystals of a single mineral species. The geometry of
693-935: A variety of its SiO 2 polymorphs , such as tridymite and cristobalite at high temperatures, and coesite at high pressures. Classifying minerals ranges from simple to difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex optical , chemical or X-ray diffraction analysis; these methods, however, can be costly and time-consuming. Physical properties applied for classification include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, cleavage and fracture, and specific gravity. Other less general tests include fluorescence , phosphorescence , magnetism , radioactivity , tenacity (response to mechanical induced changes of shape or form), piezoelectricity and reactivity to dilute acids . Crystal structure results from
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#1733085570609756-498: A variety of minerals because of the need to balance charges. Because the eight most common elements make up over 98% of the Earth's crust, the small quantities of the other elements that are typically present are substituted into the common rock-forming minerals. The distinctive minerals of most elements are quite rare, being found only where these elements have been concentrated by geological processes, such as hydrothermal circulation , to
819-595: A white mica, can be used for windows (sometimes referred to as isinglass), as a filler, or as an insulator. Ores are minerals that have a high concentration of a certain element, typically a metal. Examples are cinnabar (HgS), an ore of mercury; sphalerite (ZnS), an ore of zinc; cassiterite (SnO 2 ), an ore of tin; and colemanite , an ore of boron . Gems are minerals with an ornamental value, and are distinguished from non-gems by their beauty, durability, and usually, rarity. There are about 20 mineral species that qualify as gem minerals, which constitute about 35 of
882-429: Is a purple variety of the mineral species quartz . Some mineral species can have variable proportions of two or more chemical elements that occupy equivalent positions in the mineral's structure; for example, the formula of mackinawite is given as (Fe,Ni) 9 S 8 , meaning Fe x Ni 9- x S 8 , where x is a variable number between 0 and 9. Sometimes a mineral with variable composition
945-707: Is a sedimentary rock composed primarily of organically derived carbon. In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals. The major examples of these are quartz, the feldspars , the micas , the amphiboles , the pyroxenes , the olivines , and calcite; except for the last one, all of these minerals are silicates. Overall, around 150 minerals are considered particularly important, whether in terms of their abundance or aesthetic value in terms of collecting. Commercially valuable minerals and rocks, other than gemstones, metal ores, or mineral fuels, are referred to as industrial minerals . For example, muscovite ,
1008-445: Is in octahedral coordination. Other examples are the aluminosilicates kyanite , andalusite , and sillimanite (polymorphs, since they share the formula Al 2 SiO 5 ), which differ by the coordination number of the Al ; these minerals transition from one another as a response to changes in pressure and temperature. In the case of silicate materials, the substitution of Si by Al allows for
1071-459: Is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with a capital letter. For some groups of organisms, their orders may follow consistent naming schemes . Orders of plants , fungi , and algae use
1134-408: Is possible for one element to be substituted for another. Chemical substitution will occur between ions of a similar size and charge; for example, K will not substitute for Si because of chemical and structural incompatibilities caused by a big difference in size and charge. A common example of chemical substitution is that of Si by Al , which are close in charge, size, and abundance in the crust. In
1197-470: Is possible for two rocks to have an identical or a very similar bulk rock chemistry without having a similar mineralogy. This process of mineralogical alteration is related to the rock cycle . An example of a series of mineral reactions is illustrated as follows. Orthoclase feldspar (KAlSi 3 O 8 ) is a mineral commonly found in granite , a plutonic igneous rock . When exposed to weathering, it reacts to form kaolinite (Al 2 Si 2 O 5 (OH) 4 ,
1260-653: Is split into separate species, more or less arbitrarily, forming a mineral group ; that is the case of the silicates Ca x Mg y Fe 2- x - y SiO 4 , the olivine group . Besides the essential chemical composition and crystal structure, the description of a mineral species usually includes its common physical properties such as habit , hardness , lustre , diaphaneity , colour, streak , tenacity , cleavage , fracture , parting, specific gravity , magnetism , fluorescence , radioactivity , as well as its taste or smell and its reaction to acid . Minerals are classified by key chemical constituents;
1323-524: Is the angle opposite the a-axis, viz. the angle between the b and c axes): The hexagonal crystal family is also split into two crystal systems – the trigonal , which has a three-fold axis of symmetry, and the hexagonal, which has a six-fold axis of symmetry. Chemistry and crystal structure together define a mineral. With a restriction to 32 point groups, minerals of different chemistry may have identical crystal structure. For example, halite (NaCl), galena (PbS), and periclase (MgO) all belong to
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#17330855706091386-422: Is the generally recognized standard body for the definition and nomenclature of mineral species. As of November 2024 , the IMA recognizes 6,100 official mineral species. The chemical composition of a named mineral species may vary somewhat due to the inclusion of small amounts of impurities. Specific varieties of a species sometimes have conventional or official names of their own. For example, amethyst
1449-405: Is the hardest natural substance, has an adamantine lustre, and belongs to the isometric crystal family, whereas graphite is very soft, has a greasy lustre, and crystallises in the hexagonal family. This difference is accounted for by differences in bonding. In diamond, the carbons are in sp hybrid orbitals, which means they form a framework where each carbon is covalently bonded to four neighbours in
1512-456: Is typical of garnet, prismatic (elongated in one direction), and tabular, which differs from bladed habit in that the former is platy whereas the latter has a defined elongation. Related to crystal form, the quality of crystal faces is diagnostic of some minerals, especially with a petrographic microscope. Euhedral crystals have a defined external shape, while anhedral crystals do not; those intermediate forms are termed subhedral. The hardness of
1575-628: The Prodromus Systematis Naturalis Regni Vegetabilis of Augustin Pyramus de Candolle and the Genera Plantarum of Bentham & Hooker, it indicated taxa that are now given the rank of family (see ordo naturalis , ' natural order '). In French botanical publications, from Michel Adanson 's Familles naturelles des plantes (1763) and until the end of the 19th century, the word famille (plural: familles )
1638-614: The CIPW norm , which gives reasonable estimates for volcanic rock formed from dry magma. The chemical composition may vary between end member species of a solid solution series. For example, the plagioclase feldspars comprise a continuous series from sodium -rich end member albite (NaAlSi 3 O 8 ) to calcium -rich anorthite (CaAl 2 Si 2 O 8 ) with four recognized intermediate varieties between them (given in order from sodium- to calcium-rich): oligoclase , andesine , labradorite , and bytownite . Other examples of series include
1701-496: The hydrosphere , atmosphere , and biosphere . The group's scope includes mineral-forming microorganisms, which exist on nearly every rock, soil, and particle surface spanning the globe to depths of at least 1600 metres below the sea floor and 70 kilometres into the stratosphere (possibly entering the mesosphere ). Biogeochemical cycles have contributed to the formation of minerals for billions of years. Microorganisms can precipitate metals from solution , contributing to
1764-451: The 78 mineral classes listed in the Dana classification scheme. Skinner's (2005) definition of a mineral takes this matter into account by stating that a mineral can be crystalline or amorphous. Although biominerals are not the most common form of minerals, they help to define the limits of what constitutes a mineral proper. Nickel's (1995) formal definition explicitly mentioned crystallinity as
1827-431: The IMA's decision to exclude biogenic crystalline substances. For example, Lowenstam (1981) stated that "organisms are capable of forming a diverse array of minerals, some of which cannot be formed inorganically in the biosphere." Skinner (2005) views all solids as potential minerals and includes biominerals in the mineral kingdom, which are those that are created by the metabolic activities of organisms. Skinner expanded
1890-455: The IMA. They are most commonly named after a person , followed by discovery location; names based on chemical composition or physical properties are the two other major groups of mineral name etymologies. Most names end in "-ite"; the exceptions are usually names that were well-established before the organization of mineralogy as a discipline, for example galena and diamond . A topic of contention among geologists and mineralogists has been
1953-548: The Latin species , "a particular sort, kind, or type with distinct look, or appearance". The abundance and diversity of minerals is controlled directly by their chemistry, in turn dependent on elemental abundances in the Earth. The majority of minerals observed are derived from the Earth's crust . Eight elements account for most of the key components of minerals, due to their abundance in the crust. These eight elements, summing to over 98% of
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2016-488: The aluminium abundance is unusually high, the excess aluminium will form muscovite or other aluminium-rich minerals. If silicon is deficient, part of the feldspar will be replaced by feldspathoid minerals. Precise predictions of which minerals will be present in a rock of a particular composition formed at a particular temperature and pressure requires complex thermodynamic calculations. However, approximate estimates may be made using relatively simple rules of thumb , such as
2079-449: The bulk chemistry of the parent body. For example, in most igneous rocks, the aluminium and alkali metals (sodium and potassium) that are present are primarily found in combination with oxygen, silicon, and calcium as feldspar minerals. However, if the rock is unusually rich in alkali metals, there will not be enough aluminium to combine with all the sodium as feldspar, and the excess sodium will form sodic amphiboles such as riebeckite . If
2142-424: The case of limestone, and quartz in the latter case. Other rocks can be defined by relative abundances of key (essential) minerals; a granite is defined by proportions of quartz, alkali feldspar , and plagioclase feldspar . The other minerals in the rock are termed accessory minerals , and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal
2205-415: The coordination of the silicate is by a number: in the case of the silica tetrahedron, the silicon is said to have a coordination number of 4. Various cations have a specific range of possible coordination numbers; for silicon, it is almost always 4, except for very high-pressure minerals where the compound is compressed such that silicon is in six-fold (octahedral) coordination with oxygen. Bigger cations have
2268-417: The crust by weight, are, in order of decreasing abundance: oxygen , silicon , aluminium , iron , magnesium , calcium , sodium and potassium . Oxygen and silicon are by far the two most important – oxygen composes 47% of the crust by weight, and silicon accounts for 28%. The minerals that form are those that are most stable at the temperature and pressure of formation, within the limits imposed by
2331-434: The difference in charge has to accounted for by making a second substitution of Si by Al . Coordination polyhedra are geometric representations of how a cation is surrounded by an anion. In mineralogy, coordination polyhedra are usually considered in terms of oxygen, due its abundance in the crust. The base unit of silicate minerals is the silica tetrahedron – one Si surrounded by four O . An alternate way of describing
2394-414: The dipyramidal point group. These differences arise corresponding to how aluminium is coordinated within the crystal structure. In all minerals, one aluminium ion is always in six-fold coordination with oxygen. Silicon, as a general rule, is in four-fold coordination in all minerals; an exception is a case like stishovite (SiO 2 , an ultra-high pressure quartz polymorph with rutile structure). In kyanite,
2457-468: The ending -anae that was initiated by Armen Takhtajan 's publications from 1966 onwards. The order as a distinct rank of biological classification having its own distinctive name (and not just called a higher genus ( genus summum )) was first introduced by the German botanist Augustus Quirinus Rivinus in his classification of plants that appeared in a series of treatises in the 1690s. Carl Linnaeus
2520-517: The example of plagioclase, there are three cases of substitution. Feldspars are all framework silicates, which have a silicon-oxygen ratio of 2:1, and the space for other elements is given by the substitution of Si by Al to give a base unit of [AlSi 3 O 8 ] ; without the substitution, the formula would be charge-balanced as SiO 2 , giving quartz. The significance of this structural property will be explained further by coordination polyhedra. The second substitution occurs between Na and Ca ; however,
2583-888: The field of zoology , the Linnaean orders were used more consistently. That is, the orders in the zoology part of the Systema Naturae refer to natural groups. Some of his ordinal names are still in use, e.g. Lepidoptera (moths and butterflies) and Diptera (flies, mosquitoes, midges, and gnats). In virology , the International Committee on Taxonomy of Viruses 's virus classification includes fifteen taxomomic ranks to be applied for viruses , viroids and satellite nucleic acids : realm , subrealm , kingdom , subkingdom, phylum , subphylum , class, subclass, order, suborder, family, subfamily , genus, subgenus , and species. There are currently fourteen viral orders, each ending in
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2646-745: The formation of ore deposits. They can also catalyze the dissolution of minerals. Prior to the International Mineralogical Association's listing, over 60 biominerals had been discovered, named, and published. These minerals (a sub-set tabulated in Lowenstam (1981) ) are considered minerals proper according to Skinner's (2005) definition. These biominerals are not listed in the International Mineral Association official list of mineral names; however, many of these biomineral representatives are distributed amongst
2709-498: The former Veneroida into other orders, such as the new Cardiida (for Cardioidea and Tellinoidea ) and Carditida (cockles and their allies). Venerids are generally thick-valved, equal-valved and isomyarian (that is, their adductor muscles are of equal size). Three main hinge teeth are characteristic of the subclass Heterodonta , to which this order belongs. Many species are active rather than sessile. However, they tend to be filter feeders , feeding through paired siphons , with
2772-410: The generic AX 2 formula; these two groups are collectively known as the pyrite and marcasite groups. Polymorphism can extend beyond pure symmetry content. The aluminosilicates are a group of three minerals – kyanite , andalusite , and sillimanite – which share the chemical formula Al 2 SiO 5 . Kyanite is triclinic, while andalusite and sillimanite are both orthorhombic and belong to
2835-451: The hexaoctahedral point group (isometric family), as they have a similar stoichiometry between their different constituent elements. In contrast, polymorphs are groupings of minerals that share a chemical formula but have a different structure. For example, pyrite and marcasite , both iron sulfides, have the formula FeS 2 ; however, the former is isometric while the latter is orthorhombic. This polymorphism extends to other sulfides with
2898-461: The material to be a stable or metastable solid at room temperature (25 °C). However, the IMA only requires that the substance be stable enough for its structure and composition to be well-determined. For example, it has recently recognized meridianiite (a naturally occurring hydrate of magnesium sulfate ) as a mineral, even though it is formed and stable only below 2 °C. As of November 2024 , 6,100 mineral species are approved by
2961-489: The most common gemstones. Gem minerals are often present in several varieties, and so one mineral can account for several different gemstones; for example, ruby and sapphire are both corundum , Al 2 O 3 . The first known use of the word "mineral" in the English language ( Middle English ) was the 15th century. The word came from Medieval Latin : minerale , from minera , mine, ore. The word "species" comes from
3024-428: The most encompassing of these being the six crystal families. These families can be described by the relative lengths of the three crystallographic axes, and the angles between them; these relationships correspond to the symmetry operations that define the narrower point groups. They are summarized below; a, b, and c represent the axes, and α, β, γ represent the angle opposite the respective crystallographic axis (e.g. α
3087-402: The olivine series of magnesium-rich forsterite and iron-rich fayalite, and the wolframite series of manganese -rich hübnerite and iron-rich ferberite . Chemical substitution and coordination polyhedra explain this common feature of minerals. In nature, minerals are not pure substances, and are contaminated by whatever other elements are present in the given chemical system. As a result, it
3150-622: The orderly geometric spatial arrangement of atoms in the internal structure of a mineral. This crystal structure is based on regular internal atomic or ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see or are irregularly shaped, the underlying crystal structure is always periodic and can be determined by X-ray diffraction. Minerals are typically described by their symmetry content. Crystals are restricted to 32 point groups , which differ by their symmetry. These groups are classified in turn into more broad categories,
3213-563: The point where they can no longer be accommodated in common minerals. Changes in temperature and pressure and composition alter the mineralogy of a rock sample. Changes in composition can be caused by processes such as weathering or metasomatism ( hydrothermal alteration ). Changes in temperature and pressure occur when the host rock undergoes tectonic or magmatic movement into differing physical regimes. Changes in thermodynamic conditions make it favourable for mineral assemblages to react with each other to produce new minerals; as such, it
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#17330855706093276-447: The presence of repetitive twinning; however, instead of occurring around a rotational axis, polysynthetic twinning occurs along parallel planes, usually on a microscopic scale. Crystal habit refers to the overall shape of crystal. Several terms are used to describe this property. Common habits include acicular, which describes needlelike crystals as in natrolite , bladed, dendritic (tree-pattern, common in native copper ), equant, which
3339-560: The previous definition of a mineral to classify "element or compound, amorphous or crystalline, formed through biogeochemical processes," as a mineral. Recent advances in high-resolution genetics and X-ray absorption spectroscopy are providing revelations on the biogeochemical relations between microorganisms and minerals that may shed new light on this question. For example, the IMA-commissioned "Working Group on Environmental Mineralogy and Geochemistry " deals with minerals in
3402-420: The same position. Michael Benton (2005) inserted them between superorder and magnorder instead. This position was adopted by Systema Naturae 2000 and others. In botany , the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order. Any number of further ranks can be used as long as they are clearly defined. The superorder rank is commonly used, with
3465-485: The second aluminium is in six-fold coordination; its chemical formula can be expressed as Al Al SiO 5 , to reflect its crystal structure. Andalusite has the second aluminium in five-fold coordination (Al Al SiO 5 ) and sillimanite has it in four-fold coordination (Al Al SiO 5 ). Differences in crystal structure and chemistry greatly influence other physical properties of the mineral. The carbon allotropes diamond and graphite have vastly different properties; diamond
3528-505: The sense of chemistry (such as mellite ). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite ) that also occur in rocks. The concept of mineral is distinct from rock , which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral or may be an aggregate of two or more different types of minerals, spacially segregated into distinct phases . Some natural solid substances without
3591-717: The suffix -ales (e.g. Dictyotales ). Orders of birds and fishes use the Latin suffix -iformes meaning 'having the form of' (e.g. Passeriformes ), but orders of mammals and invertebrates are not so consistent (e.g. Artiodactyla , Actiniaria , Primates ). For some clades covered by the International Code of Zoological Nomenclature , several additional classifications are sometimes used, although not all of these are officially recognized. In their 1997 classification of mammals , McKenna and Bell used two extra levels between superorder and order: grandorder and mirorder . Michael Novacek (1986) inserted them at
3654-473: The suffix -virales . Mineral In geology and mineralogy , a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form. The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite ) or organic compounds in
3717-439: The twinning is controlled by the mineral's symmetry. As a result, there are several types of twins, including contact twins, reticulated twins, geniculated twins, penetration twins, cyclic twins, and polysynthetic twins. Contact, or simple twins, consist of two crystals joined at a plane; this type of twinning is common in spinel. Reticulated twins, common in rutile, are interlocking crystals resembling netting. Geniculated twins have
3780-468: The two dominant systems are the Dana classification and the Strunz classification. Silicate minerals comprise approximately 90% of the Earth's crust . Other important mineral groups include the native elements , sulfides , oxides , halides , carbonates , sulfates , and phosphates . The International Mineralogical Association has established the following requirements for a substance to be considered
3843-574: The word family ( familia ) was assigned to the rank indicated by the French famille , while order ( ordo ) was reserved for a higher rank, for what in the 19th century had often been named a cohors (plural cohortes ). Some of the plant families still retain the names of Linnaean "natural orders" or even the names of pre-Linnaean natural groups recognized by Linnaeus as orders in his natural classification (e.g. Palmae or Labiatae ). Such names are known as descriptive family names. In
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#17330855706093906-543: Was the first to apply it consistently to the division of all three kingdoms of nature (then minerals , plants , and animals ) in his Systema Naturae (1735, 1st. Ed.). For plants, Linnaeus' orders in the Systema Naturae and the Species Plantarum were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. When the word ordo was first consistently used for natural units of plants, in 19th-century works such as
3969-540: Was used as a French equivalent for this Latin ordo . This equivalence was explicitly stated in the Alphonse Pyramus de Candolle 's Lois de la nomenclature botanique (1868), the precursor of the currently used International Code of Nomenclature for algae, fungi, and plants . In the first international Rules of botanical nomenclature from the International Botanical Congress of 1905,
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