The eudicots, Eudicotidae or eudicotyledons are a clade of flowering plants, called tricolpates or non-magnoliid dicots by previous authors. The botanical terms were introduced in 1991 by evolutionary botanist James A. Doyle and paleobotanist Carol L. Hotton to emphasize the evolutionary divergence of tricolpate dicots from earlier, less specialized, dicots; the close relationships among flowering plants with tricolpate pollen grains was seen in morphological studies of shared derived characters. These plants have a distinct trait in their pollen grains of exhibiting three colpi or grooves paralleling the polar axis. Molecular evidence confirmed the genetic basis for the evolutionary relationships among flowering plants with tricolpate pollen grains and dicotyledonous traits; the term means "true dicotyledons", as it contains the majority of plants that have been considered dicots and have characteristics of the dicots. The term "eudicots" has subsequently been adopted in botany to refer to one of the two largest clades of angiosperms, monocots being the other.
The remaining angiosperms include magnoliids and what are sometimes referred to as basal angiosperms or paleodicots, but these terms have not been or adopted, as they do not refer to a monophyletic group. The other name for the eudicots is tricolpates, a name which refers to the grooved structure of the pollen. Members of the group have tricolpate pollen; these pollens have three or more pores set in furrows called colpi. In contrast, most of the other seed plants produce monosulcate pollen, with a single pore set in a differently oriented groove called the sulcus; the name "tricolpates" is preferred by some botanists to avoid confusion with the dicots, a nonmonophyletic group. Numerous familiar plants are eudicots, including many common food plants and ornamentals; some common and familiar eudicots include members of the sunflower family such as the common dandelion, the forget-me-not and other members of its family, buttercup and macadamia. Most leafy trees of midlatitudes belong to eudicots, with notable exceptions being magnolias and tulip trees which belong to magnoliids, Ginkgo biloba, not an angiosperm.
The name "eudicots" is used in the APG system, of 1998, APG II system, of 2003, for classification of angiosperms. It is applied to a monophyletic group, which includes most of the dicots. "Tricolpate" is a synonym for the "Eudicot" monophyletic group, the "true dicotyledons". The number of pollen grain furrows or pores helps classify the flowering plants, with eudicots having three colpi, other groups having one sulcus. Pollen apertures are any modification of the wall of the pollen grain; these modifications include thinning and pores, they serve as an exit for the pollen contents and allow shrinking and swelling of the grain caused by changes in moisture content. The elongated apertures/ furrows in the pollen grain are called colpi, along with pores, are a chief criterion for identifying the pollen classes; the eudicots can be divided into two groups: the basal eudicots and the core eudicots. Basal eudicot is an informal name for a paraphyletic group; the core eudicots are a monophyletic group.
A 2010 study suggested the core eudicots can be divided into two clades, Gunnerales and a clade called "Pentapetalae", comprising all the remaining core eudicots. The Pentapetalae can be divided into three clades: Dilleniales superrosids consisting of Saxifragales and rosids superasterids consisting of Santalales, Berberidopsidales and asteridsThis division of the eudicots is shown in the following cladogram: The following is a more detailed breakdown according to APG IV, showing within each clade and orders: clade Eudicots order Ranunculales order Proteales order Trochodendrales order Buxales clade Core eudicots order Gunnerales order Dilleniales clade Superrosids order Saxifragales clade Rosids order Vitales clade Fabids order Fabales order Rosales order Fagales order Cucurbitales order Oxalidales order Malpighiales order Celastrales order Zygophyllales clade Malvids order Geraniales order Myrtales order Crossosomatales order Picramniales order Malvales order Brassicales order Huerteales order Sapindales clade Superasterids order Berberidopsidales order Santalales order Caryophyllales clade Asterids order Cornales order Ericales clade Campanulids order Aquifoliales order Asterales order Escalloniales order Bruniales order Apiales order Dipsacales order Paracryphiales clade Lamiids order Solanales order Lamiales order Vahliales order Gentianales order Boraginales order Garryales order Metteniusales order Icacinales Eudicots at the Encyclopedia of Life Eudicots, Tree of Life Web Project Dicots Plant Life Forms
Tsuga canadensis known as eastern hemlock, eastern hemlock-spruce or Canadian hemlock, in the French-speaking regions of Canada as pruche du Canada, is a coniferous tree native to eastern North America. It is the state tree of Pennsylvania; the eastern hemlock grows well in shade and is long lived, with the oldest recorded specimen, found in Tionesta, being at least 554 years old. The tree reaches heights of about 31 m, but exceptional trees have been recorded up to 53 m; the diameter of the trunk at breast height is 1.5 m, but again, outstanding trees have been recorded up to 1.75 m. The trunk is straight and monopodial, but rarely is forked; the crown is broadly conic, while the brownish bark is scaly and fissured with age. The twigs are a yellow-brown in color with darker red-brown pulvini, are densely pubescent; the buds are ovoid in shape and are small, measuring only 1.5 to 2.5 mm in length. These are not resinous, but may be so; the leaves are 15 to 20 mm in length, but may be as short as 5 mm or as long as 25 mm.
They are flattened and are distichous, or two-ranked. The bottom of the leaf is glaucous with two broad and visible stomatal bands, while the top is a shiny green to yellow-green in color; the leaf margins are slightly toothed near the apex. The seed cones are ovoid in shape and measure 1.5 to 2.5 cm in length and 1.0 to 1.5 cm in width. The scales are ovate to measure 8 to 12 mm in length by 7.0 to 10 mm in width. The apex is more or less rounded and is projected outward. Twenty-four diploid chromosomes are present within the trees' DNA; the wood is soft, coarse-grained, light buff in color. Air-dried, a cubic foot weighs 28 lbs; the lumber is used for general construction and crates. Because of its unusual power of holding spikes, it is used for railroad ties. Untreated, the wood is not durable; as a fuel, it is low in value. The wood is a source of pulp for paper manufacturing. T. canadensis occurs at sea level in the north of its distribution, but is found at elevations of 600–1,800 m. It ranges from northeastern Minnesota eastward through southern Quebec and into Nova Scotia, south in the Appalachian Mountains to northern Georgia and Alabama.
Disjunct populations occur in the southeastern Piedmont, western Ohio and into Illinois, as well as eastern Minnesota. In Canada, it is present in all provinces to the east except Newfoundland and Labrador. In the USA, it is found in all states east of and including Minnesota, Indiana, Kentucky and Alabama, but excluding Florida, its range overlaps that of the related Tsuga caroliniana. It is found on rocky ridges and hillsides with high levels of moisture. Eastern hemlock is confined to areas with cool and humid climates. Precipitation in the areas where it grows is 740 mm to more than 1,270 mm per year; the lower number is more typical of northern forests. Near the Atlantic coast and in the southern Appalachians where the trees reach their greatest heights, annual rainfall exceeds 1,520 mm. In the north of its range, the temperatures in January average −12 °C, while in July they average only 16 °C. In these areas, the frost-free season can last fewer than 80 days. In contrast, the southern end of the range experiences up to 200 days without frost and January temperatures as high as 6 °C.
The species is threatened by the hemlock woolly adelgid, a sap-sucking bug accidentally introduced from East Asia to the United States in 1924, first found in the native range of eastern hemlock in the late 1960s. The adelgid has spread rapidly in southern parts of the range once becoming established, while its expansion northward is much slower. All the hemlocks in the southern Appalachian Mountains have seen infestations of the insect within the last five to seven years, with thousands of hectares of stands dying within the last two to three years. Attempts to save representative examples on both public and private lands are on-going. A project named "Tsuga Search", funded by the Great Smoky Mountains National Park, is being conducted to save the largest and tallest remaining eastern hemlocks in the Park. Through Tsuga Search, hemlocks have been found with trunk volumes up to 44.8 m³ within the park, making it the largest eastern evergreen conifer, eclipsing in volume both eastern white pine and loblolly pine.
The tree is listed as a least concern species in the IUCN Red List, but this is based on its wide distribution and because the adelgid populations have not reached the northern areas of its range. A 2009 study conducted by scientists with the U. S. Forest Service Southern Research Station suggests the hemlock woolly adelgid is killing hemlock trees faster than expected in the southern Appalachians, altering the carbon cycle of these forests. According to Science Daily, the pest could kill most of the region's hemlock trees within the next decade. According to the study, researchers found "hemlock woolly adelgid infestation is impacting the carbon cycle in tree stands," and "adelgid-infested hemlock trees in the South are declining much faster than the reported 9-year decline of some infested hemlock trees in the Northeast." In a 2009 case study, entom
Fagaceae is a family of flowering plants that includes beeches and oaks, comprises eight genera with about 927 species. The Fagaceae are deciduous or evergreen trees and shrubs, characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, fruit in the form of cup-like nuts, their leaves are lobed and both petioles and stipules are present. Leaf characteristics of Fagaceae can be similar to those of Rosaceae and other rose motif families, their fruits lack endosperm and lie in a scaly or spiny husk that may or may not enclose the entire nut, which may consist of one to seven seeds. In the oaks, genus Quercus, the fruit is a non-valved nut called an acorn; the husk of the acorn in most oaks only forms a cup. Other members of the family have enclosed nuts. Fagaceae is one of the most ecologically important woody plant families in the Northern Hemisphere, as oaks form the backbone of temperate forest in North America and Asia and one of the most significant sources of wildlife fodder.
Several members of the Fagaceae have important economic uses. Many species of oak and beech are used as timber for floors, furniture and wine barrels. Cork for stopping wine bottles and myriad other uses is made from the bark of cork oak, Quercus suber. Chestnuts are the fruits from species of the genus Castanea. Numerous species from several genera are prominent ornamentals, wood chips from the genus Fagus are used in flavoring beers; the Fagaceae are divided into five or six subfamilies and are accepted to include 8 genera. Monophyly of the Fagaceae is supported by both morphological and molecular data; the Southern Hemisphere genus Nothofagus the southern beeches, was placed in the Fagaceae sister to the genus Fagus, but recent molecular evidence suggests otherwise. While Nothofagus shares a number of common characteristics with the Fagaceae, such as cupule fruit structure, it differs in a number of ways, including distinct stipule and pollen morphology, as well as having a different number of chromosomes.
The accepted view by systematic botanists is to place Nothofagus in its own family, Nothofagaceae. Fagoideae K. Koch Fagus L.—beeches. 1754—chestnuts. 1948—golden chinkapins. H. Oh 2008 —Tanoaks; the genus Nothofagus included in the Fagaceae, is now treated in the separate family Nothofagaceae. The Fagaceae are distributed across the Northern Hemisphere. Genus-level diversity is concentrated in Southeast Asia, where most of the extant genera are thought to have evolved before migrating to Europe and North America. Members of the Fagaceae are ecologically dominant in northern temperate forests. Modern molecular phylogenetics suggest the following relationships: Fagaceae in Topwalks Family Fagaceae - diagnostic photos of many species at The Morton Arboretum
Florida is the southernmost contiguous state in the United States. The state is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Atlantic Ocean, to the south by the Straits of Florida. Florida is the 22nd-most extensive, the 3rd-most populous, the 8th-most densely populated of the U. S. states. Jacksonville is the most populous municipality in the state and the largest city by area in the contiguous United States; the Miami metropolitan area is Florida's most populous urban area. Tallahassee is the state's capital. Florida's $1.0 trillion economy is the fourth largest in the United States. If it were a country, Florida would be the 16th largest economy in the world, the 58th most populous as of 2018. In 2017, Florida's per capita personal income was ranking 26th in the nation; the unemployment rate in September 2018 was 3.5% and ranked as the 18th in the United States. Florida exports nearly $55 billion in goods made in the 8th highest among all states.
The Miami Metropolitan Area is by far the largest urban economy in Florida and the 12th largest in the United States with a GDP of $344.9 billion as of 2017. This is more than twice the number of the next metro area, the Tampa Bay Area, which has a GDP of $145.3 billion. Florida is home to 51 of the world's billionaires with most of them residing in South Florida; the first European contact was made in 1513 by Spanish explorer Juan Ponce de León, who called it la Florida upon landing there in the Easter season, known in Spanish as Pascua Florida. Florida was a challenge for the European colonial powers before it gained statehood in the United States in 1845, it was a principal location of the Seminole Wars against the Native Americans, racial segregation after the American Civil War. Today, Florida is distinctive for its large Cuban expatriate community and high population growth, as well as for its increasing environmental issues; the state's economy relies on tourism and transportation, which developed in the late 19th century.
Florida is renowned for amusement parks, orange crops, winter vegetables, the Kennedy Space Center, as a popular destination for retirees. Florida is the flattest state in the United States. Lake Okeechobee is the largest freshwater lake in the U. S. state of Florida. Florida's close proximity to the ocean influences many aspects of daily life. Florida is a reflection of multiple inheritance. Florida has attracted many writers such as Marjorie Kinnan Rawlings, Ernest Hemingway and Tennessee Williams, continues to attract celebrities and athletes, it is internationally known for golf, auto racing, water sports. Several beaches in Florida have emerald-colored coastal waters. About two-thirds of Florida occupies a peninsula between the Gulf of the Atlantic Ocean. Florida has the longest coastline in the contiguous United States 1,350 miles, not including the contribution of the many barrier islands. Florida has a total of 4,510 islands; this is the second-highest number of islands of any state of the United States.
It is the only state that borders both the Gulf of the Atlantic Ocean. Much of the state is characterized by sedimentary soil. Florida has the lowest high point of any U. S. state. The climate varies from subtropical in the north to tropical in the south; the American alligator, American crocodile, American flamingo, Roseate spoonbill, Florida panther, bottlenose dolphin, manatee can be found in Everglades National Park in the southern part of the state. Along with Hawaii, Florida is one of only two states that has a tropical climate, is the only continental state with either a tropical climate or a coral reef; the Florida Reef is the only living coral barrier reef in the continental United States, the third-largest coral barrier reef system in the world. By the 16th century, the earliest time for which there is a historical record, major Native American groups included the Apalachee of the Florida Panhandle, the Timucua of northern and central Florida, the Ais of the central Atlantic coast, the Tocobaga of the Tampa Bay area, the Calusa of southwest Florida and the Tequesta of the southeastern coast.
Florida was the first region of the continental United States to be visited and settled by Europeans. The earliest known European explorers came with the Spanish conquistador Juan Ponce de León. Ponce de León spotted and landed on the peninsula on April 2, 1513, he named the region Florida. The story that he was searching for the Fountain of Youth is mythical and only appeared long after his death. In May 1539, Conquistador Hernando de Soto skirted the coast of Florida, searching for a deep harbor to land, he described seeing a thick wall of red mangroves spread mile after mile, some reaching as high as 70 feet, with intertwined and elevated roots making landing difficult. The Spanish introduced Christianity, horses, the Castilian language, more to Florida. Spain established several settlements with varying degrees of success. In 1559, Don Tristán de Luna y Arellano established a settlement at present-day Pensacola, making it the first attempted settlement in Florida, but it was abandoned by 1561.
In 1565, the settlement of St. Augustine was established under the leadership of admiral and
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
North America is a continent within the Northern Hemisphere and all within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands are included. North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge 40,000 to 17,000 years ago; the so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago. The Classic stage spans the 6th to 13th centuries.
The Pre-Columbian era ended in 1492, the transatlantic migrations—the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect interactions between European colonists, indigenous peoples, African slaves and their descendants. Owing to the European colonization of the Americas, most North Americans speak English, Spanish or French, their culture reflects Western traditions; the Americas are accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass unknown by Europeans. In 1507, Waldseemüller produced a world map, in which he placed the word "America" on the continent of South America, in the middle of what is today Brazil, he explained the rationale for the name in the accompanying book Cosmographiae Introductio:... ab Americo inventore... quasi Americi terram sive Americam.
For Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespucci's name, but in its feminine form "America", following the examples of "Europa", "Asia" and "Africa". Other mapmakers extended the name America to the northern continent, In 1538, Gerard Mercator used America on his map of the world for all the Western Hemisphere; some argue that because the convention is to use the surname for naming discoveries, the derivation from "Amerigo Vespucci" could be put in question. In 1874, Thomas Belt proposed a derivation from the Amerrique mountains of Central America. Marcou corresponded with Augustus Le Plongeon, who wrote: "The name AMERICA or AMERRIQUE in the Mayan language means, a country of perpetually strong wind, or the Land of the Wind, and... the can mean... a spirit that breathes, life itself." The United Nations formally recognizes "North America" as comprising three areas: Northern America, Central America, The Caribbean.
This has been formally defined by the UN Statistics Division. The term North America maintains various definitions in accordance with context. In Canadian English, North America refers to the land mass as a whole consisting of Mexico, the United States, Canada, although it is ambiguous which other countries are included, is defined by context. In the United States of America, usage of the term may refer only to Canada and the US, sometimes includes Greenland and Mexico, as well as offshore islands. In France, Portugal, Romania and the countries of Latin America, the cognates of North America designate a subcontinent of the Americas comprising Canada, the United States, Mexico, Greenland, Saint Pierre et Miquelon, Bermuda. North America has been referred to by other names. Spanish North America was referred to as Northern America, this was the first official name given to Mexico. Geographically the North American continent has many subregions; these include cultural and geographic regions. Economic regions included those formed by trade blocs, such as the North American Trade Agreement bloc and Central American Trade Agreement.
Linguistically and culturally, the continent could be divided into Latin America. Anglo-America includes most of Northern America and Caribbean islands with English-speaking populations; the southern North American continent is composed of two regions. These are the Caribbean; the north of the continent maintains recognized regions as well. In contrast to the common definition of "North America", which encompasses the whole continent, the term "North America" is sometimes used to refer only to Mexico, the United States, Greenland; the term Northern America refers to the northern-most countries and territories of North America: the United States, Bermuda, St. Pierre and Miquelon and Greenland. Although the term does not refer to a unifie
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