The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any
The British Isles are a group of islands in the North Atlantic off the north-western coast of continental Europe that consist of the islands of Great Britain, the Isle of Man, the Hebrides and over six thousand smaller isles. They have a total area of about 315,159 km2 and a combined population of 72 million, include two sovereign states, the Republic of Ireland, the United Kingdom of Great Britain and Northern Ireland; the islands of Alderney, Jersey and Sark, their neighbouring smaller islands, are sometimes taken to be part of the British Isles though, as islands off the coast of France, they do not form part of the archipelago. The oldest rocks in the group are in the north west of Scotland and North Wales and are 2.7 billion years old. During the Silurian period, the north-western regions collided with the south-east, part of a separate continental landmass; the topography of the islands is modest in scale by global standards. Ben Nevis rises to an elevation of only 1,345 metres, Lough Neagh, notably larger than other lakes in the island group, covers 390 square kilometres.
The climate is temperate marine, with warm summers. The North Atlantic drift brings significant moisture and raises temperatures 11 °C above the global average for the latitude; this led to a landscape, long dominated by temperate rainforest, although human activity has since cleared the vast majority of forest cover. The region was re-inhabited after the last glacial period of Quaternary glaciation, by 12,000 BC, when Great Britain was still part of a peninsula of the European continent. Ireland, which became an island by 12,000 BC, was not inhabited until after 8000 BC. Great Britain became an island by 5600 BC. Hiberni and Britons tribes, all speaking Insular Celtic, inhabited the islands at the beginning of the 1st millennium AD. Much of Brittonic-occupied Britain was conquered by the Roman Empire from AD 43; the first Anglo-Saxons arrived as Roman power waned in the 5th century, dominated the bulk of what is now England. Viking invasions began in the 9th century, followed by more permanent settlements and political change in England.
The Norman conquest of England in 1066 and the Angevin partial conquest of Ireland from 1169 led to the imposition of a new Norman ruling elite across much of Britain and parts of Ireland. By the Late Middle Ages, Great Britain was separated into the Kingdoms of England and Kingdom of Scotland, while control in Ireland fluxed between Gaelic kingdoms, Hiberno-Norman lords and the English-dominated Lordship of Ireland, soon restricted only to The Pale; the 1603 Union of the Crowns, Acts of Union 1707 and Acts of Union 1800 attempted to consolidate Britain and Ireland into a single political unit, the United Kingdom of Great Britain and Ireland, with the Isle of Man and the Channel Islands remaining as Crown Dependencies. The expansion of the British Empire and migrations following the Irish Famine and Highland Clearances resulted in the dispersal of some of the islands' population and culture throughout the world, a rapid depopulation of Ireland in the second half of the 19th century. Most of Ireland seceded from the United Kingdom after the Irish War of Independence and the subsequent Anglo-Irish Treaty, with six counties remaining in the UK as Northern Ireland.
The term "British Isles" is controversial in Ireland, where there are nationalist objections to its usage. The Government of Ireland does not recognise the term, its embassy in London discourages its use. Britain and Ireland is used as an alternative description, Atlantic Archipelago has seen limited use in academia; the earliest known references to the islands as a group appeared in the writings of sea-farers from the ancient Greek colony of Massalia. The original records have been lost. In the 1st century BC, Diodorus Siculus has Prettanikē nēsos, "the British Island", Prettanoi, "the Britons". Strabo used Βρεττανική, Marcian of Heraclea, in his Periplus maris exteri, used αἱ Πρεττανικαί νῆσοι to refer to the islands. Historians today, though not in absolute agreement agree that these Greek and Latin names were drawn from native Celtic-language names for the archipelago. Along these lines, the inhabitants of the islands were called the Πρεττανοί; the shift from the "P" of Pretannia to the "B" of Britannia by the Romans occurred during the time of Julius Caesar.
The Greco-Egyptian scientist Claudius Ptolemy referred to the larger island as great Britain and to Ireland as little Britain in his work Almagest. In his work, Geography, he gave these islands the names Alwion and Mona, suggesting these may have been names of the individual islands not known to him at the time of writing Almagest; the name Albion appears to have fallen out of use sometime after the Roman conquest of Great Britain, after which Britain became the more commonplace name for the island called Great Britain. The earliest known use of the phrase Brytish Iles in the English language is dated 1577 in a work by John Dee. Today, this name is seen by some as carrying imperialist overtones although it is still used. Other names used to describe the islands include the Anglo-Celtic Isles, Atlantic archipelago, British-Irish Isles and Ireland, UK
Binomial nomenclature called binominal nomenclature or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomen, binominal name or a scientific name; the first part of the name – the generic name – identifies the genus to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong within this genus to the species Homo sapiens. Tyrannosaurus rex is the most known binomial; the formal introduction of this system of naming species is credited to Carl Linnaeus beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus; the application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature for animals and the International Code of Nomenclature for algae and plants.
Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules. In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not when derived from a proper noun such as the name of a person or place. Both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a binomial name is given, at least when it is first mentioned, the date of publication may be specified. In zoology "Patella vulgata Linnaeus, 1758"; the name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet. "Passer domesticus". The original name given by Linnaeus was Fringilla domestica; the ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs include such information.
In botany "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus". "Hyacinthoides italica Rothm. – Linnaeus first named this bluebell species Scilla italica. The name is composed of two word-forming elements: "bi", a Latin prefix for two, "-nomial", relating to a term or terms; the word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics. Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name, from one to several words long. Together they formed a system of polynomial nomenclature; these names had two separate functions. First, to designate or label the species, second, to be a diagnosis or description. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; such "polynomial names" may sometimes look like binomials, but are different. For example, Gerard's herbal describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort.
The other... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels; the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more known by his Latinized name Carl Linnaeus, it was in his 1753 Species Plantarum that he first began using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as specific name; the Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. Linnaeus's trivial names introduced an important new idea, namely that the function of a name could be to give a species a unique label; this meant. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virgi
A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Leaves are collectively referred to as foliage, as in "autumn foliage". A leaf is a thin, dorsiventrally flattened organ borne above ground and specialized for photosynthesis. In most leaves, the primary photosynthetic tissue, the palisade mesophyll, is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves have distinct upper surface and lower surface that differ in colour, the number of stomata, the amount and structure of epicuticular wax and other features. Leaves can have many different shapes and textures; the broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. In the clubmosses, with different evolutionary origins, the leaves are simple and are known as microphylls.
Some leaves, such as bulb scales, are not above ground. In many aquatic species the leaves are submerged in water. Succulent plants have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not homologous with them. Examples include flattened plant stems called phylloclades and cladodes, flattened leaf stems called phyllodes which differ from leaves both in their structure and origin; some structures of non-vascular plants function much like leaves. Examples include the phyllids of liverworts. Leaves are the most important organs of most vascular plants. Green plants are autotrophic, meaning that they do not obtain food from other living things but instead create their own food by photosynthesis, they capture the energy in sunlight and use it to make simple sugars, such as glucose and sucrose, from carbon dioxide and water. The sugars are stored as starch, further processed by chemical synthesis into more complex organic molecules such as proteins or cellulose, the basic structural material in plant cell walls, or metabolised by cellular respiration to provide chemical energy to run cellular processes.
The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf, while leaves are orientated to maximise their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the plant shoots and roots. Vascular plants transport sucrose in a special tissue called the phloem; the phloem and xylem are parallel to each other but the transport of materials is in opposite directions. Within the leaf these vascular systems branch to form veins which supply as much of the leaf as possible, ensuring that cells carrying out photosynthesis are close to the transportation system. Leaves are broad and thin, thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts, thus promoting photosynthesis.
They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance plants adapted to windy conditions may have pendent leaves, such as in many willows and eucalyptss; the flat, or laminar, shape maximises thermal contact with the surrounding air, promoting cooling. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of transpiration, providing the energy required to draw the transpiration stream up from the roots, guttation. Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost; these are interpreted as reduced from megaphyllous leaves of their Devonian ancestors. Some leaf forms are adapted to modulate the amount of light they absorb to avoid or mitigate excessive heat, ultraviolet damage, or desiccation, or to sacrifice light-absorption efficiency in favour of protection from herbivory.
For xerophytes the major constraint drought. Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. and Bulbine mesembryanthemoides. Leaves function to store chemical energy and water and may become specialised organs serving other functions, such as tendrils of peas and other legumes, the protective spines of cacti and the insect traps in carnivorous plants such as Nepenthes and Sarracenia. Leaves are the fundamental structural units from which cones are constructed in gymnosperms and from which flowers are constructed in flowering plants; the internal organisation of most kinds of leaves has evolved to maximise exposure of the photosynthetic organelles, the chloroplasts, to light and to increase the absorption of carbon dioxide while at the same time controlling water loss. Their surfaces are waterproofed by the plant cuticle and gas exchange between the mesophyll cells and the atmosphere is controlled by minute openings called stomata which open or close to regulate the rate exchange of carbon dioxide and water vapour into
Missouri Botanical Garden
The Missouri Botanical Garden is a botanical garden located at 4344 Shaw Boulevard in St. Louis, Missouri, it is known informally as Shaw's Garden for founder and philanthropist Henry Shaw. Its herbarium, with more than 6.6 million specimens, is the second largest in North America, behind only that of the New York Botanical Garden. Founded in 1859, the Missouri Botanical Garden is one of the oldest botanical institutions in the United States and a National Historic Landmark, it is listed in the National Register of Historic Places. The Garden is a center for botanical research and science education of international repute, as well as an oasis in the city of St. Louis, with 79 acres of horticultural display, it includes a 14-acre Japanese strolling garden named Seiwa-en. It is adjacent to another of Shaw's legacies. In 1983, the Botanical Garden was added as the fourth subdistrict of the Metropolitan Zoological Park and Museum District. For part of 2006, the Missouri Botanical Garden featured "Glass in the Garden", with glass sculptures by Dale Chihuly placed throughout the garden.
Four pieces were purchased to remain at the gardens. In 2008 sculptures of the French artist Niki de Saint Phalle were placed throughout the garden. In 2009, the 150th anniversary of the Garden was celebrated, including a floral clock display. After 40 years of service to the Garden, Dr. Peter Raven retired from his presidential post on September 1, 2010. Dr. Peter Wyse Jackson replaced him as President; the Garden is a place for many annual cultural festivals, including the Japanese Festival and the Chinese Culture Days by the St. Louis Chinese Culture Days Committee. During this time, there are showcases of the culture's botanics as well as cultural arts, crafts and food; the Japanese Festival features sumo wrestling, taiko drumming, koma-mawashi top spinning, kimono fashion shows. The Garden is known for its bonsai growing, which can be seen all year round, but is highlighted during the multiple Asian festivals. Major garden features include: Tower Grove House and Herb Garden - Shaw's Victorian country house designed by prominent local architect George I.
Barnett in the Italianate style. Victory of Science Over Ignorance - Marble statue by Carlo Nicoli. Linnean House - Said to be the oldest continually operated greenhouse west of the Mississippi River. Shaw's orangery, in the late 1930s it was converted to house camellias. Gladney Rose Garden - Circular rose garden with arbors. Climatron and Reflecting Pools - the world's first geodesic dome greenhouse designed by architect and engineer Thomas C. Howard of Synergetics, Inc. English Woodland Garden - aconite, bluebells, hosta and others beneath the tree canopy. Seiwa-en Japanese Garden - is a 14-acre chisen kaiyu-shiki with lawns and path set around a 4-acre central lake, it is the largest Japanese Garden in North America. Grigg Nanjing Friendship Chinese Garden - Designed by architect Yong Pan. Blanke Boxwood Garden - walled parterre with a fine boxwood collection. Strassenfest German Garden - flora native to Germany and Central Europe. Ottoman garden with water xeriscape. Douglas Trumbull, director of the 1972 science fiction classic film Silent Running, stated that the geodesic domes on the spaceship Valley Forge were based on the Missouri Botanical Garden's Climatron dome.
Missouri Botanical Garden operates the Sophia M. Sachs Butterfly House in Chesterfield; the Butterfly House includes an 8,000-square-foot indoor butterfly conservatory as well as an outdoor butterfly garden. The EarthWays Center is a group at the Missouri Botanical Garden that provides resources on and educates the public about green practices, renewable energy, energy efficiency, other sustainability matters; the Shaw Nature Reserve was started by the Missouri Botanical Garden in 1925 as a place to store plants away from the pollution of the city. The air in St. Louis cleared up, the reserve has continued to be open to the public for enjoyment and education since; the 2,400-acre reserve is located in Missouri, 35 miles away from the city. The Plant List is an Internet encyclopedia project to compile a comprehensive list of botanical nomenclature, created by the Royal Botanic Gardens and the Missouri Botanical Garden; the Plant List has 1,040,426 scientific plant names of species rank, of which 298,900 are accepted species names.
In addition, the list has 16,167 plant genera. Monsanto has donated $10 million to the Missouri Botanical Garden since the 1970s, which named its 1998 plant science facility the'Monsanto Center'. List of botanical gardens in the United States Peter F. Stevens, a biologist working in the Missouri Botanical Garden Annals of the Missouri Botanical Garden, journal St. Louis Chinese Culture Day List of National Historic Landmarks in Missouri N
Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans insects and other arthropods. Carnivorous plants have adapted to grow in places where the soil is thin or poor in nutrients nitrogen, such as acidic bogs. Charles Darwin wrote Insectivorous Plants, the first well-known treatise on carnivorous plants, in 1875. True carnivory is thought to have evolved independently nine times in five different orders of flowering plants, is represented by more than a dozen genera; this classification includes at least 583 species that attract and kill prey, absorbing the resulting available nutrients. Additionally, over 300 protocarnivorous plant species in several genera show some but not all of these characteristics. Five basic trapping mechanisms are found in carnivorous plants. Pitfall traps trap prey in a rolled leaf that contains a pool of digestive bacteria. Flypaper traps use a sticky mucilage. Snap traps utilize rapid leaf movements.
Bladder traps suck in prey with a bladder. Lobster traps known as eel traps, force prey to move towards a digestive organ with inward-pointing hairs; these traps may be passive, depending on whether movement aids the capture of prey. For example, Triphyophyllum is a passive flypaper that secretes mucilage, but whose leaves do not grow or move in response to prey capture. Meanwhile, sundews are active flypaper traps whose leaves undergo rapid acid growth, an expansion of individual cells as opposed to cell division; the rapid acid growth allows the sundew tentacles to bend, aiding in the retention and digestion of prey. The sundew species Drosera glanduligera employs a unique trapping mechanism with features of both flypaper and snap traps. Characterized by an internal chamber, pitfall traps are thought to have evolved independently at least six times; this particular adaptation is found within the families Sarraceniaceae, Nepenthaceae and Eriocaulaceae. Within the family Bromeliaceae, pitcher morphology and carnivory evolved twice.
Because these families do not share a common ancestor who had pitfall trap morphology, carnivorous pitchers are an example of convergent evolution. A passive trap, pitfall traps attract prey with nectar bribes secreted by the peristome and bright flower-like anthocyanin patterning within the pitcher; the linings of most pitcher plants are covered in a loose coating of waxy flakes which are slippery for insects, causing them to fall into the pitcher. Once within the pitcher structure, digestive enzymes or mutualistic species break down the prey into an absorbable form for the plant. Water can become trapped within the pitcher, making a habitat for other fauna; this type of'water body' is called a Phytotelma. The simplest pitcher plants are those of Heliamphora, the marsh pitcher plant. In this genus, the traps are derived from a simple rolled leaf whose margins have sealed together; these plants live in areas of high rainfall in South America such as Mount Roraima and have a problem ensuring their pitchers do not overflow.
To counteract this problem, natural selection has favoured the evolution of an overflow similar to that of a bathroom sink—a small gap in the zipped-up leaf margins allows excess water to flow out of the pitcher. Heliamphora is a member of a New World family in the order Ericales. Heliamphora is limited to South America, but the family contains two other genera and Darlingtonia, which are endemic to the Southeastern United States and California respectively. Sarracenia purpurea subsp. Purpurea can be found as far north as Canada. Sarracenia is the pitcher plant genus most encountered in cultivation, because it is hardy and easy to grow. In the genus Sarracenia, the problem of pitcher overflow is solved by an operculum, a flared leaflet that covers the opening of the rolled-leaf tube and protects it from rain; because of this improved waterproofing, Sarracenia species secrete enzymes such as proteases and phosphatases into the digestive fluid at the bottom of the pitcher. The enzymes digest the proteins and nucleic acids in the prey, releasing amino acids and phosphate ions, which the plant absorbs.
In at least one species, Sarracenia flava, the nectar bribe is laced with coniine, a toxic alkaloid found in hemlock, which increases the efficiency of the traps by intoxicating prey. Darlingtonia californica, the cobra plant, possesses an adaptation found in Sarracenia psittacina and, to a lesser extent, in Sarracenia minor: the operculum is balloon-like and seals the opening to the tube; this balloon-like chamber is pitted with areolae, chlorophyll-free patches through which light can penetrate. Insects ants, enter the chamber via the opening underneath the balloon. Once inside, they tire themselves trying to escape from these false exits, until they fall into the tube. Prey access is increased by the "fish tails", outgrowths of the operculum that give the plant its name; some seedling Sarracenia species have long, overhanging opercular outgrowths. The second major group of pitcher plants are the monkey cups or tropical pitcher plants of the genus Nepenthes. In the hundred or so species of this genus, the pitcher is borne at the end of a tendril, which grows as an extension to the midrib o
In botanical nomenclature, a form is one of the "secondary" taxonomic ranks, below that of variety, which in turn is below that of species. If more than three ranks are listed in describing a taxon, the "classification" is being specified, but only three parts make up the "name" of the taxon: a genus name, a specific epithet, an infraspecific epithet; the abbreviation "f." or the full "forma" should be put before the infraspecific epithet to indicate the rank. It is not italicised. For example: Acanthocalycium spiniflorum f. klimpelianum or Acanthocalycium spiniflorum forma klimpelianum Donald Crataegus aestivalis Torr. & A. Gray var. cerasoides Sarg. f. luculenta Sarg. is a classification of a plant whose name is: Crataegus aestivalis Torr. & A. Gray f. luculenta Sarg. A form designates a group with a noticeable morphological deviation; the usual taxonomic practice is that the individuals classified within the form are not known to be related. For instance, white-flowered plants of species that have coloured flowers can be grouped and named.
Formae apomicticae are sometimes named among plants. There are theoretically countless numbers of forms based on minor genetic differences, only a few that have particular significance are to be named. Form Forma specialis, an informal rank used for a parasitic form adapted to a particular host Trinomial nomenclature Variety Subvariety Plant variety Cultivar Hybrid Race