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Gaelic football

Gaelic football (Peil Ghaelach; short name Peil), commonly known as simply Gaelic, GAA or football is an Irish team sport. A form of football, it is played between two teams of 15 players on a rectangular grass pitch. The objective of the sport is to score by kicking or punching the ball into the other team's goal (3 points) or between two upright posts above the goal and over a crossbar 2.5 m above the ground (1 point).

Players advance the ball up the field with a combination of carrying, bouncing, kicking, hand-passing, and soloing (dropping the ball and then toe-kicking the ball upward into the hands). In the game, two types of scores are possible: points and goals. A point is awarded for kicking or hand-passing the ball over the crossbar, signalled by the umpire raising a white flag. A goal is awarded for kicking the ball under the crossbar into the net (the ball cannot be hand-passed into the goal), signalled by the umpire raising a green flag. Positions in Gaelic football are similar to those in other football codes and comprise one goalkeeper, six backs, two midfielders, and six forwards, with a variable number of substitutes.

Gaelic football is one of four sports (collectively referred to as the "Gaelic games") controlled by the Gaelic Athletic Association (GAA), the largest sporting organisation in Ireland. Along with hurling and camogie, Gaelic football is one of the few remaining strictly amateur sports in the world, with players, coaches, and managers prohibited from receiving any form of payment. Gaelic football is mainly played on the island of Ireland, although units of the Association exist in Great Britain, mainland Europe, North America, Africa, Asia and Oceania.

The final of the All-Ireland Senior Championship, held every year at Croke Park, Dublin, draws crowds of more than 80,000 people. Outside Ireland, football is mainly played among members of the Irish diaspora. A notable exception is France, where it has been growing lately, not least in the Celtic region of Brittany. Gaelic Park in New York City is the largest purpose-built Gaelic sports venue outside Ireland. Three major football competitions operate throughout the year: the National Football League and the All-Ireland Senior Championship operate on an inter-county basis, while the All-Ireland Club Championship is contested by individual clubs. The All-Ireland Senior Championship is considered the most prestigious event in Gaelic football.

Under the auspices of the GAA, Gaelic football is a male-only sport; however, the related sport of ladies' Gaelic football is governed by the Ladies' Gaelic Football Association.

Similarities between Gaelic football and Australian rules football have allowed the development of international rules football, a hybrid sport, and a series of Test matches has been held regularly since 1998.

History
While Gaelic football as it is known today dates back to the late 19th century, various kinds of football were played in Ireland before this time.

Ancient Mob football (caid)
The first legal reference to football in Ireland was in 1308, when John McCrocan, a spectator at a football game at Novum Castrum de Leuan (the New Castle of the Lyons or Newcastle), was charged with accidentally stabbing a player named William Bernard. A field near Newcastle, South Dublin is still known as the football field. The Statute of Galway of 1527 allowed the playing of "foot balle" and archery but banned "hokie'—the hurling of a little ball with sticks or staves" as well as other sports.

By the 17th century, the situation had changed considerably. The games had grown in popularity and were widely played. This was due to the patronage of the gentry. Now instead of opposing the games it was the gentry and the ruling class who were serving as patrons of the games. Games were organised between landlords with each team comprising 20 or more tenants. Wagers were commonplace with purses of up to 100 guineas (Prior, 1997).

The earliest record of a recognised precursor to the modern game dates from a match in County Meath in 1670, in which catching and kicking the ball were permitted.

However even "foot-ball" was banned by the severe Sunday Observance Act of 1695, which imposed a fine of one shilling (a substantial amount at the time) for those caught playing sports. It proved difficult, if not impossible, for the authorities to enforce the Act and the earliest recorded inter-county match in Ireland was one between Louth and Meath, at Slane, in 1712, about which the poet Séamas Dall Mac Cuarta wrote a poem of 88 verses beginning "Ba haigeanta".

A six-a-side version was played in Dublin in the early 18th century, and 100 years later there were accounts of games played between County sides (Prior, 1997).

By the early 19th century, various football games, referred to collectively as caid, were popular in County Kerry, especially the Dingle Peninsula. Father W. Ferris described two forms of caid: the "field game" in which the object was to put the ball through arch-like goals, formed from the boughs of two trees, and; the epic "cross-country game", which lasted the whole of a Sunday (after mass) and was won by taking the ball across a parish boundary. "Wrestling", "holding" opposing players, and carrying the ball were all allowed.

Accounts from the Irish diaspora
Some accounts of traditional Irish football come not from Ireland, but from the Irish diaspora, often in celebrating traditional events such as St Patrick's Day. The largest such communities existed in Britain, the United States, Australia, and New Zealand. Many of the earliest football matches in Australia date back to the 1840s amongst Irish immigrants. In the Colony of South Australia, there are several accounts of Irish football being played at Thebarton in 1843 and again in 1853. There were similar accounts of football in the 1840s in the Colony of Victoria including Melbourne at Batman's Hill and the goldfields in the Colony of Victoria. The account of H C A Harrison, one of the seminal in the history of Victorian football, of Irish rules was that it gave players "the full ability to kick anybody that came within reach". Shin-kicking (or hacking) was a major feature of traditional Irish football and also one of the main reasons why it failed to be widely adopted in Australia. Irish football was also played in the Colony of New Zealand in the 1860s and 1870s in Auckland during Thomas Croke's term as Archbishop there. An 1882 theatrical performance in New York portrays a controversial Irish football match on Saint Nicholas Day 6 December 1790 at the school of Champs de Mars in Paris. Despite a large Irish population references to it being played in America before the 1880s are scant. USGAA makes the unsourced claim that matches were played at Hyde Park, San Francisco in the 1850s.

First appearance of modern football
During the 1860s and 1870s, rugby football started to become popular in Ireland. Trinity College Dublin was an early stronghold of rugby, and the rules of the (English) Football Association were codified in 1863 and distributed widely. By this time, according to Gaelic football historian Jack Mahon, even in the Irish countryside, caid had begun to give way to a "rough-and-tumble game", which even allowed tripping.

The first account of what the founders of modern Gaelic football referred to as Irish football dates to 1873. Paddy Begley notes that in County Kerry in 1870 only soccer and rugby were played, although historian Paddy Foley notes that by 1874 a third, very different form of football began to emerge and spread across South-West Ireland. At Killarney, these highly popular matches were virtually indistinguishable from the Victorian Rules (first codified in 1859 and then played extensively in the Colony of Victoria and Colony of Queensland and to a lesser extent in the colonies of New South Wales and New Zealand). This kicking variety of football was even played with an oval ball which became customary in Australia in the 1870s and that scoring was achieved only by kicking goals. A major difference between the two styles is that the Irish variety featured high kicking "up and under" whereas in colonial Victoria, the little marks or foot passes were much more common. While the founders of the game were all familiar with or played rugby, including Cusack and Davin, few had played Irish football as it was so rare outside of the South-West, though the influence of this football on the founders was obvious, this is most likely the "football kicking under the Irish rules" that Thomas Croke later recalled in County Cork.

Irish historian Garnham, citing R.M. Peter's Irish Football Annual of 1880, argued that Gaelic football did not exist before the 1880s and curious about the origin of the distinctive features believed that clubs from England in 1868 most likely introduced elements of their codes including the "mark" (a free kick to players who cleanly catch the ball, which was a feature of the matches played in the 1880s), lack of offside and scoring by kicking between the upright posts. Unable to identify the source of these peculiar traits he concluded that they must have been introduced by Trinity, Cambridge (those known as the 1858 Cambridge Rules) and Blackheath (1862 club rules).

County Limerick was a stronghold of the game in the 1880s, and the Commercials Club in Limerick, founded by employees of Cannock's Drapery Store, was one of the first to impose a set of rules, which was adapted by other clubs in the city. These rules are believed to be the basis for the rules that were later adopted by the GAA and appear to have contained some of the Victorian Rules of 1866. It is not known how or when these Victorian Rules reached Ireland, though many of the goldrush Irish immigrants returned to Ireland during the 1870s and 1880s as the colonial fortunes faded. At a similar point in time, the same football rules were proposed as an alternative to those of soccer and rugby in northern England but did not take root there. Playing the code under its own rules the club (representing County Limerick) later won the inaugural 1887 All-Ireland Senior Football Championship Final.

English (Association) football started to take hold, especially in Ulster, in the 1880s. By the mid-1880s it had become so popular that it was feared by many to completely displace Irish football.

Irish football, however, continued its grip on the southern counties. Accounts from 1889 state that the variety of football that was becoming popular in Ireland in 1884 bore little resemblance at all to the old mob football and was received by the public as more a hybrid of English and Scotch football.

Codification and Administration
Irish forms of football were not formally arranged into an organised playing code by the Gaelic Athletic Association (GAA) until 1884 with the rules widely distributed in 1887. The GAA sought to promote traditional Irish sports, such as hurling, and to reject "foreign" (particularly English) imports. The first Gaelic football rules, showing the influence of hurling (and incorporating some of the Victorian Rules of 1866 and 1877  ) represented the strong desire to differentiate from association football (and rugby)—for example in their lack of an offside rule. The rules were first drawn up by Maurice Davin in 1884 and later published in the United Ireland magazine on 7 February 1887. The original rules bear many similarities to modern football with the requirement to kick, handpass, and the basic scoring system, however, the original rules also included many Australian features including additional scoring posts (removed later in 1910 ). The code had already begun to diverge, with the mark being deprecated, the soccer ball being adopted, and carrying the ball not allowed, as such there was no requirement to bounce or solo the ball carrying the ball remained illegal until the turn of the 20th century. The game was intended to promote peace and harmony, rejecting the violence of other football codes, and Davin even included a requirement for players to hold hands with their opponents though this practice fell out of favour.

The first game of Gaelic football under GAA rules (developed by Maurice Davin) was played near Callan, Co Kilkenny in February 1885. From 1886 the GAA banned tackling.

GAA rules of 1887
The widely published GAA rules were as follows: 1. The ground for full teams (21 aside) shall be 140 yards long by 84 yards broad, or as near that size as can be got. The ground must be properly marked by boundary lines. Boundary lines are to be at least five yards from the fences. Note— There is no objection to a larger ground.

2. There shall not be less than 14 or more than 21 players a side in regular matches.

3. There shall be two umpires and a referee. Where the umpires disagree the referee's decision shall be final. There shall also be a goal umpire at each end of the ground to watch for goals and points. The referee shall keep the time, and throw up the ball at the commencement of each goal.

4. The goalposts shall stand at each end in the centre of the goal line. They shall be 21 feet apart, with a crossbar 8 feet from the ground. Besides the goal posts, there shall be two upright posts standing in each goal line 21 feet from the goal posts. A goal is won when the ball is driven between the goalposts and under the crossbar. A point is counted when the ball is driven over the crossbar, or the goal line, within 21 feet of either goal post.

5. The captains of the teams shall toss for choice of sides before commencing play, and the players shall stand in two ranks opposite each other in the centre of the field until the ball is thrown up, each holding the hand of one of the other side.

6. Pushing or tripping behind, holding from behind, catching below knees, or butting with the head, shall be deemed foul, and the player so offending shall be ordered to stand aside for such time as the referee may think fit, and his side cannot substitute another man. Wrestling shall not be allowed.

7. The time of actual play shall be one hour, and sides are to be changed only at half-time.

8. When a player drives the ball over the sideline, it shall be thrown back from the point where it first crossed the line by a player on the opposite side. It may be thrown in any direction. When the ball is driven over the goal line, and not through the goal, the goalkeeper shall have a free kick from the goal, and no player on the opposite side to approach nearer than the 21-yard line until the ball is kicked. If the ball is driven over the goal line by a player whose goal line it is, it shall count one point for the opposite side; if driven over the goal line within 21 feet of either goal post, it shall count three points; if through the goal it shall count a goal.

9. The match shall be decided by the greater number of goals. When no goal is made, or when the goals are even, it shall be decided by the greater number of points.

10. The ball must be struck with the hand. It may be caught when off the ground, and the player catching it may kick it any way he pleases, but must not carry it or throw it forward. Note. — There is nothing in this rule to prevent a player from throwing the ball a little in front to allow himself more freedom in kicking it.

11. Where the rules are broken the referee may allow a free kick if he thinks fit. In such a free kick the ball must be kicked from the ground. No player on the opposite side is to approach nearer than 14 yards until the ball is kicked; but if the free kick is allowed nearer than 14 yards of the goal line, the opposite players need not stand behind that line.

12. If the ball strikes a bystander near the sideline, except the referee or umpire, it shall be considered out of play and must be thrown in as directed in Rule 8. If it occurs near the goal line it shall be considered out of play and must be kicked from the goal. In the latter case, the referee may allow one point or more if he thinks fit.

13. The referee shall have, during the match, full power to disqualify any player or order him to stand aside and discontinue play, for any act he may consider unfair, as set out in Rule 6, or for vicious play.

No nails or iron tips are allowed on the boots. Strips of leather fastened on the soles will prevent slipping. The dress for hurling and football is to be knee breeches and stockings and shoes or boots.

Game spreads

Gaelic football spread throughout the world in the late 19th century. Despite a huge Irish American population there was limited awareness of the game in America, though there was limited knowledge of its rules, apart from that the ball cannot be lifted from the ground by hand, and throttling is banned. It was first played in North America in the 1890s with games being played in both Canada and the United States in 1892. More than a dozen clubs had been established in the US by 1893. The first clubs appeared in England in 1896.

Around 1900 the game began to resemble more closely to the running game of today, players were able to lift the ball off the ground and run and carry it if they bounced it every 4 yards.

The first match played in Australia was in 1902 finding a niche in Queensland during a period when Australian football there was in recess.

Increasing nationalism
Some Gaelic Athletic Associations began to impose strict nationalistic policies during this time. For example, in Connacht free kicks began to be introduced into some leagues penalising speaking of any language but Irish, and imposing a rule that the referee may speak only in Irish.

On Bloody Sunday in 1920, during the Irish War of Independence, a football match at Croke Park was attacked by the Royal Irish Constabulary (RIC), including its Auxiliary Division. 14 people were killed and 65 were injured. Among the dead was Tipperary footballer Michael Hogan, for whom the Hogan Stand at Croke Park (completed in 1924) was named.

In 1930 the GAA banned children found playing rugby instead of Gaelic football.

20th century Gaelic football
In 1939, at Yankee Stadium in New York City, Kerry played Galway in front of a crowd of 70,000 spectators.

By 1958, Wembley Stadium hosted annual exhibition games of Gaelic football in England, before tens of thousands of spectators.

Ladies' Gaelic football has become increasingly popular with women since the 1970s.

Interactions with Australia (1967–)
In 1967, Australian journalist, broadcaster, and VFL umpire Harry Beitzel, inspired by watching the 1966 All-Ireland senior football final on television, sent an Australian team known as the "Galahs" including South Melbourne's Bob Skilton, Richmond's Royce Hart, Carlton's Alex Jesaulenko and Melbourne and Carlton legend Ron Barassi as captain-coach – to play against Mayo and All-Ireland champions Meath, which was the first recorded major interaction between the two codes.

What then followed is the current International Rules Series between players of both codes and utilizing rules from both codes, which also gives them a chance to represent their country. The GAA chooses the team to represent Ireland, while the AFL chooses the team to represent Australia and has added a stipulation that each member of their team must have been named an All-Australian at least once. The two countries take turns hosting the series, and both countries' and sports' respective most prestigious venues – Croke Park and the Melbourne Cricket Ground (MCG) – have hosted series Tests. What is known as the Irish experiment also occurred, with Australian rules football clubs recruiting Gaelic football players. Irishmen who have distinguished themselves in both codes include Dublin's Jim Stynes – a 1984 minor All-Ireland football champion who became the 1991 Brownlow Medallist, a recipient of the Medal of the Order of Australia and a member of Melbourne's Team of the Century – and Kerry's Tadhg Kennelly, the first man to become both a senior All-Ireland football champion (2009) and an AFL Premiership player (2005 with Sydney, the Swans' first flag in 72 years).

Overview
Players advance the football up the field with a combination of carrying, bouncing, kicking, hand-passing, and soloing (dropping the ball and then toe-kicking it upward into the hands). In the game, two types of scores are possible: points and goals. A point is awarded for kicking or hand-passing the ball over the crossbar, signalled by the umpire raising a white flag. A goal is awarded for kicking the ball under the crossbar into the net, signalled by the umpire raising a green flag. Positions in Gaelic football are similar to those in other football codes and comprise one goalkeeper, six backs, two midfielders, and six forwards, with a variable number of substitutes.

Playing field
A Gaelic pitch is similar in some respects to a rugby pitch but larger. The grass pitch is rectangular, stretching 130 - 145 m long and 80 - 90 m wide. There are H-shaped goalposts at each end, formed by two posts, which are usually 6 - 7 m high, set 6.5 m apart, and connected 2.5 m above the ground by a crossbar. A net extending behind the goal is attached to the crossbar and lower goalposts. The same pitch is used for hurling; the GAA, which organises both sports, decided this to facilitate dual usage. Lines are marked at distances of 13 m, 20 m, and 45 m (65 m in hurling) from each end-line. Shorter pitches and smaller goals are used by youth teams.

Duration
The majority of adult football and all minor and under-21 matches last for 60 minutes, divided into two halves of 30 minutes, except for senior inter-county games, which last for 70 minutes (two halves of 35 minutes). Draws are decided by replays or by playing 20 minutes of extra time (two halves of 10 minutes). Juniors have halves of 20 minutes or 25 minutes in some cases. Half-time intermission lasts from 5 to 15 minutes. Championship matches have a 30-minute intermission.

Teams
Teams consist of fifteen players (a goalkeeper, two corner backs, a full back, two wing backs, a centre back, two midfielders, two wing forwards, a centre forward, two corner forwards and a full forward) plus up to fifteen substitutes, of which six may be used. As for younger teams or teams that do not have enough players for fifteen a side, it is not uncommon to play thirteen a side (the same positions except without the full-back and the full forward). Each player is numbered 1–15, starting with the goalkeeper, who must wear a jersey colour different from that of his or her teammates. Up to 15 substitutes may be named on the team sheet, number 16 usually being the reserve goalkeeper.

Ball
The game is played with a round leather football made of 18 stitched leather panels, with a circumference of 68 - 70 cm, weighing between 480 and 500 g when dry. It may be kicked or hand-passed. A hand pass is not a punch but rather a strike of the ball with the side of the closed fist, using the knuckle of the thumb.

Mark
In 2017, the GAA introduced the 'mark' across the board in Gaelic football. Similar to the mark in Australian rules football, a player who catches the ball from a kick-out is awarded a free kick. The rule in full states: "When a player catches the ball cleanly from a Kick-Out without it touching the ground, on or past the 45 m line nearest the Kick-Out point, he shall be awarded 'a Mark' by the Referee. The player awarded a 'Mark' shall have the options of (a) Taking a free kick or (b) Playing on immediately." In comparison, the Australian rules equivalent requires the ball not to have touched the ground and for the kick to have travelled at least 15 m. In the experimental rules of 2019, a player can now also call a mark inside the opposition's 45 m line after a clean catch from a kick played over 20 m from outside the 45 m line that does not touch the ground or any other player.

In 2020, additional versions of the Mark came into force in Gaelic football. The Advanced Mark allowed a ball to be fielded cleanly inside the opposition 45 when kicked forward over a distance greater than 20 m from outside the opposition 45. The referee is required to blow the whistle as this occurs, at which point the player has the option to take the Mark or play on.

There is also a Defensive Mark, which a defender can get from a long ball played into him.

Types of fouls
There are three main types of fouls in Gaelic football, which can result in the ball being given to the other team, a player being cautioned, a player being removed from the field, or even the game being terminated.

Technical fouls
The following are considered technical fouls ("fouling the ball"):
 * Going five steps without releasing, bouncing, or soloing the ball (soloing involves kicking the ball into one's own hands)
 * Bouncing the ball twice in a row (It may be soloed continuously)
 * Changing hands: Throwing the ball between the hands (legal in the ladies' game)
 * Throwing the ball (it may be "hand-passed" by striking with the fist).
 * Hand passing a goal. To hand pass a ball with an open palm there must be a clear striking action (the ball may be punched over the bar from up in the air, but not into the goal).
 * Picking the ball directly off the ground (it must be scooped up into the hands by the foot). However, in ladies' Gaelic football, the ball may be picked up directly.
 * The square ball is an often controversial rule: "If at the moment the ball enters the small square, there is already an attacking player inside the small rectangle, then a free out is awarded." As of 2012 square balls are only counted if the player is inside the square when the ball is kicked from a free or set piece. An opposing player is allowed in the square during open play.

Aggressive fouls
Aggressive fouls are physical or verbal fouls committed by a player against an opponent or the referee. The player can be cautioned (shown a yellow card), ordered off the pitch without a substitute (red card), or (as of January 2020) ejected from the match to the Sin Bin, where they must remain for ten minutes before returning to the field (black card). Picking up two black cards risks a red card, and the substitute will serve out whatever time imposed by officials.

Dissent
A dissent foul is a foul where a player fails to comply with the officials' judgment and/or instructions. The player can be cautioned (shown a yellow card), ordered off the pitch without a substitute (red card), the free kick placement moved 13 m further down-field, or in certain circumstances, the game can be terminated. The following are considered dissent fouls:
 * To challenge the authority of a referee, umpire, linesman, or sideline official.
 * To fail to comply with a referee's instruction to use an orifice guard.
 * To refuse to leave the field of play, on the instruction of the referee, for attention, after an injury involving bleeding.
 * To show dissent with the referee's decision to award a free kick to the opposing team.
 * To refuse to leave the field of play when ordered off (red card) or rejoin the game after being ordered off.
 * A team or player(s) leaving the field without the referee's permission or refusing to continue playing.

Scoring

If the ball goes over the crossbar, a point is scored and a white flag is raised by an umpire. A point is scored by either kicking the ball over the crossbar or fisting it over, in which case the hand must be closed while striking the ball. If the ball goes below the crossbar, a goal, worth three points, is scored, and a green flag is raised by an umpire. A goal is scored by kicking the ball into the net, not by fist-passing the ball into it. However, a player can strike the ball into the net with a closed fist if the ball was played to him by another player or came in contact with the post/crossbar/ground before connection. The goal is guarded by a goalkeeper. Scores are recorded in the format Goal Total-Point Total. To determine the score-line goals must be converted to points and added to the other points. For example, in a match with a final score of Team A 0–21 and Team B 4–8, Team A is the winner with 21 points, as Team B scored only 20 points (4 times 3, plus 8).

Tackling
The level of tackling allowed is less robust than in rugby or Australian rules.

Shoulder-to-shoulder contact and slapping the ball out of an opponent's hand are permitted, but the following are all fouls:
 * Blocking a shot with the foot
 * Pulling an opponent's jersey
 * Pushing an opponent
 * Sliding tackles
 * Striking an opponent
 * Touching the goalkeeper when he/she is inside the small rectangle
 * Tripping
 * Using both hands to tackle
 * Wrestling the ball from an opponent's hands

Restarting play

 * A match begins with the referee throwing the ball up between the four mid-fielders.
 * After an attacker has put the ball wide of the goals or scored a point or a goal, the goalkeeper may take a kick out from the ground at the 13 m line. All players must be beyond the 20 m line. However, in the 2019 experimental rules (rules tested in pre-season competitions), kick-outs must be taken from the 20 m line.
 * After a defender has put the ball wide of the goals, an attacker may take a "45" from the ground on the 45 m line, level with where the ball went wide.
 * After a player has put the ball over the sideline, the other team may take a sideline kick at the point where the ball left the pitch. It may be kicked from the ground or the hands. The player who is taking the sideline kick must not pass the boundary line while taking it.
 * After a player has committed a foul, the other team may take a free kick (usually shortened to "free" in reports/commentaries) at the point where the foul was committed. It may be kicked from the ground or the hands.
 * If a player has been fouled while passing the ball, the free may be taken from the point where the ball landed.
 * After a defender has committed a foul inside the large rectangle, the other team may take a penalty kick from the ground from the centre of the 11 m line. Only the goalkeeper may guard the goals.
 * If many players are struggling for the ball and it is unclear who was fouled first, the referee may throw the ball up between two opposing players.

Officials
A football match is overseen by up to eight officials:
 * The referee
 * Two linesmen
 * Sideline official/Standby linesman (often referred to as "fourth official"; inter-county games only)
 * Four umpires (two at each goal)

The referee is responsible for starting and stopping play, recording the score, awarding frees, and booking, and sending off players.

Linesmen are responsible for indicating the direction of line balls to the referee.

The fourth official is responsible for overseeing substitutions and also indicating the amount of stoppage time (signalled to him by the referee) and the players substituted using an electronic board.

The umpires are responsible for judging the scoring. They indicate to the referee whether a shot was: wide (spread both arms), a 45 m kick (raise one arm), a point (wave white flag), a square ball (cross arms) or a goal (wave green flag). A disallowed score is indicated by crossing the green and white flags.

Other officials are not obliged to indicate any misdemeanours to the referee; they are only permitted to inform the referee of violent conduct they have witnessed that has occurred without the referee's knowledge. A linesman/umpire is not permitted to inform the referee of technical fouls such as a "double bounce" or an illegal pick-up of the ball. Such decisions can only be made at the discretion of the referee.

Team of the Century
The Team of the Century was nominated in 1984 by Sunday Independent readers and selected by a panel of experts including journalists and former players. It was not chosen as part of the Gaelic Athletic Association's centenary year celebrations. The goal was to single out the best 15 players who had played the game in their respective positions. Naturally, many of the selections were hotly debated by fans around the country.

Team of the Millennium
The Team of the Millennium was a team chosen in 1999 by a panel of GAA past presidents and journalists. The goal was to single out the best 15 players who had played the game in their respective positions, since the foundation of the GAA in 1884 up to the Millennium year, 2000. Naturally, many of the selections were hotly debated by fans around the country.

Competition structure
Gaelic sports at all levels are amateur, in the sense that the athletes, even those playing at an elite level, do not receive payment for their performance.

The main competitions at all levels of Gaelic football are the League and the Championship. Of these, it is the Championship (a knock-out tournament) that tends to attain the most prestige.

The basic unit of each game is organised at the club level, which is usually arranged on a parochial basis. Local clubs compete against other clubs in their county intending to win the County Club Championship at senior, junior, or intermediate levels (for adults) or under-21, minor or under-age levels (for children). A club may field more than one team, for example, a club may field a team at the senior level and a "seconds" team at a junior or intermediate level. This format is laid out in the table below:

Clubs may come together in districts for the County Championship or compete on their own.

Though the island of Ireland was partitioned between two states by the British parliament in 1920, the organisation of Gaelic games (like that of most cultural organisations and religions) continues on an All-Ireland basis. At the national level, Ireland's Gaelic games are organised in 32 GAA counties, most of which are identical in name and extent to the 32 administrative counties on which local government throughout the island was based until the late 20th century. The term "county" is also used for some overseas GAA places, such as London and New York. Clubs are also located throughout the world, in other parts of the United States, in Great Britain, in Canada, in Asia, in Australasia and continental Europe.

The level at which county teams compete against each other is referred to as inter-county (i.e. similar to international). A county panel—a team of 15 players, plus a similar number of substitutes—is formed from the best players playing at the club level in each county. The most prestigious inter-county competition in Gaelic football is the All-Ireland Championship. The highest-level national championship is called the All-Ireland Senior Football Championship. Nearly all counties contest this tournament on an annual basis, with crowds of people thronging venues the length and breadth of Ireland—the most famous of these stadiums being Croke Park—to support their local county team, a team comprising players selected from the clubs in that county. These modified knock-out games start as provincial championships contested by counties against other counties in their respective province, the four Irish provinces of Ulster, Munster, Leinster and Connacht. The four victors in these then progress automatically to the All-Ireland series.

In the past, the team winning each provincial championship would play one of the others, at a stage known as the All-Ireland semi-finals, with the winning team from each game playing each other in the famed All-Ireland Final to determine the outright winner. A recent (the 1990s/2000s) re-organisation created a "back door" method of qualifying, with teams knocked out during the provincial rounds of the All-Ireland Championship now acquiring a second chance at glory. Now the four victorious teams at the provincial level enter the recently created All-Ireland quarter-finals instead, where they compete against the four remaining teams from the All-Ireland Qualifiers to progress to the All-Ireland semi-finals and then the All-Ireland Final. This re-organisation means that one team may defeat another team in an early stage of the championship, yet be defeated and knocked out of the tournament by the same team at a later stage. It also means a team may be defeated in an early stage of the championship, yet be crowned All-Ireland champions—as Tyrone was in 2005 and 2008.

The secondary competition at the inter-county level is the National League. The National Football League is held every spring and groups counties into four divisions according to their relative strength. As at local (county) levels of Gaelic football, the League at a national level is less prestigious than the Championship—however, in recent years attendances have grown, as has interest from the public and players. This is due in part to the 2002 adoption of a February–April timetable, in place of the former November start, as well as the provision of Division 2 final stages. Live matches are aired on the international channel Setanta Sports and the Irish language channel TG4, with highlights shown on RTÉ Two.

There are also All-Ireland championships for county teams at Junior, Under-21 and Minor levels, and provincial and national club championships, contested by the teams that win their respective county championships.

title: Gaelic football


text:
Martin Brennan (engineer)

Martin Brennan is a computer engineer who developed pioneering personal computers such as the Loki (for Sinclair Research) and the Atari Jaguar video game console.

A physics graduate of Cambridge University, he was a co-founder of Flare Technology, a design house involved in the design of the ill-fated Konix Multisystem.

Brennan initially worked for Sinclair Research where he designed the digital electronics and software in ZX Interface 1 before going on to found Flare with ex-Sinclair colleagues John Mathieson and Ben Cheese. After working at Flare on the Flare 1 and its development into the Konix Multisystem, he went on to work for Atari developing the Atari Panther and the Atari Jaguar.

In 1997 Brennan founded the "Cheap & Cheerful Chip Company" which later went on to become Global Silicon Limited.

In 2007 Brennan designed the Brennan JB7 digital jukebox produced by 3GA Ltd (Third Generation Audio). The second generation audio player, Brennan B2 with web interface, based on the Raspberry Pi chipset, is available as of 2015. In 2019, Brennan released the Brennan BB1 audio player which shares the same software and architecture of the B2 but packages it in portable radio format at a lower price. Featuring an integrated speaker and ability to run on 4 AA batteries, the BB1 is controllable via physical buttons or a smartphone/web app and can act also integrate with Spotify and Sonos.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Martin Brennan (engineer)


text:
Seed

In botany, a seed is a plant embryo and food reserve enclosed in a protective outer covering called a seed coat (testa). More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the product of the ripened ovule, after the embryo sac is fertilized by sperm from pollen, forming a zygote. The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth is halted.

The formation of the seed is the defining part of the process of reproduction in seed plants (spermatophytes). Other plants such as ferns, mosses and liverworts, do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological niches on land, from forests to grasslands both in hot and cold climates.

In the flowering plants, the ovary ripens into a fruit which contains the seed and serves to disseminate it. Many structures commonly referred to as "seeds" are actually dry fruits. Sunflower seeds are sometimes sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the so-called stone fruits (such as the peach) have a hardened fruit layer (the endocarp) fused to and surrounding the actual seed. Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed, such as an acorn or hazelnut.

History
The first land plants evolved around 468 million years ago, and reproduced using spores. The earliest seed bearing plants to appear were the gymnosperms, which have no ovaries to contain the seeds. They arose during the late Devonian period (416 million to 358 million years ago). From these early gymnosperms, seed ferns evolved during the Carboniferous period (359 to 299 million years ago); they had ovules that were borne in a cupule, which consisted of groups of enclosing branches likely used to protect the developing seed.

Published literature about seed storage, viability and its hygrometric dependence began in the early 19th century, influential works being:
 * 1832 seed storage guide in Augustin Pyramus de Candolle's Conservation des Graines, part of his 3-volume Physiologie végétale, ou Exposition des forces et des fonctions vitales des végétaux (1832, v. 2, pp. 618–626, Paris); (translated title, "Plant physiology, or Exposition of the vital forces and functions of plants")
 * 1846 viability studies by Augustin de Candolle, published in "Sur la durée relative de la faculté de germer des graines appartenant à diverses familles" (Annales des Sciences Naturelles; Botanique, 1846, III 6: 373–382); (translated title, "On the relative duration of the ability to germinate seeds belonging to various families")
 * 1897 seed hygrometric studies by Victor Jodin (Annales Agronomiques, October 1897)
 * 1912's Henry B. Guppy's 528 page "Studies in Seeds and Fruits- An Investigation with the Balance" (1912, London, England); subsequently reviewed in Science (June 1914, Washington, D.C.)

Development
[[File:Seed Development Cycle.svg|thumb|right|Stages of seed development:

I Zygote

II Proembryo

III Globular IV Heart

V Torpedo

VI Mature Embryo

Key: ''1. Endosperm 2. Zygote 3. Embryo 4. Suspensor 5. Cotyledons 6. Shoot Apical Meristem 7. Root Apical Meristem 8. Radicle 9. Hypocotyl 10. Epicotyl 11. Seed Coat'']]

Angiosperm seeds are "enclosed seeds", produced in a hard or fleshy structure called a fruit that encloses them for protection. Some fruits have layers of both hard and fleshy material. In gymnosperms, no special structure develops to enclose the seeds, which begin their development "naked" on the bracts of cones. However, the seeds do become covered by the cone scales as they develop in some species of conifer.

Angiosperm (flowering plants) seeds consist of three genetically distinct constituents: (1) the embryo formed from the zygote, (2) the endosperm, which is normally triploid, (3) the seed coat from tissue derived from the maternal tissue of the ovule. In angiosperms, the process of seed development begins with double fertilization, which involves the fusion of two male gametes with the egg cell and the central cell to form the primary endosperm and the zygote. Right after fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue. This tissue becomes the food the young plant will consume until the roots have developed after germination.

Ovule

After fertilization, the ovules develop into the seeds. The ovule consists of a number of components:
 * The funicle (funiculus, funiculi) or seed stalk which attaches the ovule to the placenta and hence ovary or fruit wall, at the pericarp.
 * The nucellus, the remnant of the megasporangium and main region of the ovule where the megagametophyte develops.
 * The micropyle, a small pore or opening in the apex of the integument of the ovule where the pollen tube usually enters during the process of fertilization.
 * The chalaza, the base of the ovule opposite the micropyle, where integument and nucellus are joined.

The shape of the ovules as they develop often affects the final shape of the seeds. Plants generally produce ovules of four shapes: the most common shape is called anatropous, with a curved shape. Orthotropous ovules are straight with all the parts of the ovule lined up in a long row producing an uncurved seed. Campylotropous ovules have a curved megagametophyte often giving the seed a tight "C" shape. The last ovule shape is called amphitropous, where the ovule is partly inverted and turned back 90 degrees on its stalk (the funicle or funiculus).

In the majority of flowering plants, the zygote's first division is transversely oriented in regards to the long axis, and this establishes the polarity of the embryo. The upper or chalazal pole becomes the main area of growth of the embryo, while the lower or micropylar pole produces the stalk-like suspensor that attaches to the micropyle. The suspensor absorbs and manufactures nutrients from the endosperm that are used during the embryo's growth.

Embryo

The main components of the embryo are:
 * The cotyledons, the seed leaves, attached to the embryonic axis. There may be one (Monocotyledons), or two (Dicotyledons). The cotyledons are also the source of nutrients in the non-endospermic dicotyledons, in which case they replace the endosperm, and are thick and leathery. In endospermic seeds, the cotyledons are thin and papery. Dicotyledons have the point of attachment opposite one another on the axis.
 * The epicotyl, the embryonic axis above the point of attachment of the cotyledon(s).
 * The plumule, the tip of the epicotyl, and has a feathery appearance due to the presence of young leaf primordia at the apex, and will become the shoot upon germination.
 * The hypocotyl, the embryonic axis below the point of attachment of the cotyledon(s), connecting the epicotyl and the radicle, being the stem-root transition zone.
 * The radicle, the basal tip of the hypocotyl, grows into the primary root.

Monocotyledonous plants have two additional structures in the form of sheaths. The plumule is covered with a coleoptile that forms the first leaf while the radicle is covered with a coleorhiza that connects to the primary root and adventitious roots form the sides. Here the hypocotyl is a rudimentary axis between radicle and plumule. The seeds of corn are constructed with these structures; pericarp, scutellum (single large cotyledon) that absorbs nutrients from the endosperm, plumule, radicle, coleoptile, and coleorhiza – these last two structures are sheath-like and enclose the plumule and radicle, acting as a protective covering.

Seed coat
The maturing ovule undergoes marked changes in the integuments, generally a reduction and disorganization but occasionally a thickening. The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant, the inner integument forms the tegmen and the outer forms the testa. (The seed coats of some monocotyledon plants, such as the grasses, are not distinct structures, but are fused with the fruit wall to form a pericarp.) The testae of both monocots and dicots are often marked with patterns and textured markings, or have wings or tufts of hair. When the seed coat forms from only one layer, it is also called the testa, though not all such testae are homologous from one species to the next. The funiculus abscisses (detaches at fixed point – abscission zone), the scar forming an oval depression, the hilum. Anatropous ovules have a portion of the funiculus that is adnate (fused to the seed coat), and which forms a longitudinal ridge, or raphe, just above the hilum. In bitegmic ovules (e.g. Gossypium described here) both inner and outer integuments contribute to the seed coat formation. With continuing maturation the cells enlarge in the outer integument. While the inner epidermis may remain a single layer, it may also divide to produce two to three layers and accumulates starch, and is referred to as the colourless layer. By contrast, the outer epidermis becomes tanniferous. The inner integument may consist of eight to fifteen layers.

As the cells enlarge, and starch is deposited in the outer layers of the pigmented zone below the outer epidermis, this zone begins to lignify, while the cells of the outer epidermis enlarge radially and their walls thicken, with nucleus and cytoplasm compressed into the outer layer. these cells which are broader on their inner surface are called palisade cells. In the inner epidermis, the cells also enlarge radially with plate like thickening of the walls. The mature inner integument has a palisade layer, a pigmented zone with 15–20 layers, while the innermost layer is known as the fringe layer.

Gymnosperms
In gymnosperms, which do not form ovaries, the ovules and hence the seeds are exposed. This is the basis for their nomenclature – naked seeded plants. Two sperm cells transferred from the pollen do not develop the seed by double fertilization, but one sperm nucleus unites with the egg nucleus and the other sperm is not used. Sometimes each sperm fertilizes an egg cell and one zygote is then aborted or absorbed during early development. The seed is composed of the embryo (the result of fertilization) and tissue from the mother plant, which also form a cone around the seed in coniferous plants such as pine and spruce.

Shape and appearance
Seeds are very diverse, and as such there are many terms are used to describe them.

Terms to describe shape

 * Bean-shaped – resembling a kidney, with lobed ends on either side of the hilum
 * Square or Oblong – angular, with all sides being either equal, or longer-than-wide
 * Triangular – three-sided, broadest below the middle
 * Elliptic or Ovate or Obovate – rounded at both ends, or egg shaped (ovate or obovate, broader at one end), being rounded but either symmetrical about the middle, or broader below the middle, or broader above the middle
 * Discoid – resembling a disc or plate, having both thickness and parallel faces and with a rounded margin)
 * Ellipsoid
 * Globose – spherical
 * Subglobose (Inflated, but less than spherical)
 * Lenticular
 * Ovoid
 * Sectoroid
 * Other common descriptors for seeds focus on color, texture, and form. Striate seeds are striped with parallel, longitudinal lines or ridges. The most common colours are brown and black, with other colours appearing less frequently. The surface texture varies from highly polished to considerably roughened. The surface may also have a variety of appendages (see Seed coat), and be described by terms such as papillate or digitiform (finger-like). A seed coat with the consistency of cork is referred to as suberose. Other terms include crustaceous (hard, thin or brittle).
 * Other common descriptors for seeds focus on color, texture, and form. Striate seeds are striped with parallel, longitudinal lines or ridges. The most common colours are brown and black, with other colours appearing less frequently. The surface texture varies from highly polished to considerably roughened. The surface may also have a variety of appendages (see Seed coat), and be described by terms such as papillate or digitiform (finger-like). A seed coat with the consistency of cork is referred to as suberose. Other terms include crustaceous (hard, thin or brittle).

Structure

A typical seed includes two basic parts:
 * 1) an embryo;
 * 2) a seed coat.

In addition, the endosperm forms a supply of nutrients for the embryo in most monocotyledons and the endospermic dicotyledons.

Seed types
Seeds have been considered to occur in many structurally different types (Martin 1946). These are based on a number of criteria, of which the dominant one is the embryo-to-seed size ratio. This reflects the degree to which the developing cotyledons absorb the nutrients of the endosperm, and thus obliterate it.

Six types occur amongst the monocotyledons, ten in the dicotyledons, and two in the gymnosperms (linear and spatulate). This classification is based on three characteristics: embryo morphology, amount of endosperm and the position of the embryo relative to the endosperm.

Embryo
In endospermic seeds, there are two distinct regions inside the seed coat, an upper and larger endosperm and a lower smaller embryo. The embryo is the fertilised ovule, an immature plant from which a new plant will grow under proper conditions. The embryo has one cotyledon or seed leaf in monocotyledons, two cotyledons in almost all dicotyledons and two or more in gymnosperms. In the fruit of grains (caryopses) the single monocotyledon is shield shaped and hence called a scutellum. The scutellum is pressed closely against the endosperm from which it absorbs food and passes it to the growing parts. Embryo descriptors include small, straight, bent, curved, and curled.

Nutrient storage
Within the seed, there usually is a store of nutrients for the seedling that will grow from the embryo. The form of the stored nutrition varies depending on the kind of plant. In angiosperms, the stored food begins as a tissue called the endosperm, which is derived from the mother plant and the pollen via double fertilization. It is usually triploid, and is rich in oil or starch, and protein. In gymnosperms, such as conifers, the food storage tissue (also called endosperm) is part of the female gametophyte, a haploid tissue. The endosperm is surrounded by the aleurone layer (peripheral endosperm), filled with proteinaceous aleurone grains.

Originally, by analogy with the animal ovum, the outer nucellus layer (perisperm) was referred to as albumen, and the inner endosperm layer as vitellus. Although misleading, the term began to be applied to all the nutrient matter. This terminology persists in referring to endospermic seeds as "albuminous". The nature of this material is used in both describing and classifying seeds, in addition to the embryo to endosperm size ratio. The endosperm may be considered to be farinaceous (or mealy) in which the cells are filled with starch, as for instance cereal grains, or not (non-farinaceous). The endosperm may also be referred to as "fleshy" or "cartilaginous" with thicker soft cells such as coconut, but may also be oily as in Ricinus (castor oil), Croton and Poppy. The endosperm is called "horny" when the cell walls are thicker such as date and coffee, or "ruminated" if mottled, as in nutmeg, palms and Annonaceae.

In most monocotyledons (such as grasses and palms) and some (endospermic or albuminous) dicotyledons (such as castor beans) the embryo is embedded in the endosperm (and nucellus), which the seedling will use upon germination. In the non-endospermic dicotyledons the endosperm is absorbed by the embryo as the latter grows within the developing seed, and the cotyledons of the embryo become filled with stored food. At maturity, seeds of these species have no endosperm and are also referred to as exalbuminous seeds. The exalbuminous seeds include the legumes (such as beans and peas), trees such as the oak and walnut, vegetables such as squash and radish, and sunflowers. According to Bewley and Black (1978), Brazil nut storage is in hypocotyl and this place of storage is uncommon among seeds. All gymnosperm seeds are albuminous.

Seed coat

The seed coat develops from the maternal tissue, the integuments, originally surrounding the ovule. The seed coat in the mature seed can be a paper-thin layer (e.g. peanut) or something more substantial (e.g. thick and hard in honey locust and coconut), or fleshy as in the sarcotesta of pomegranate. The seed coat helps protect the embryo from mechanical injury, predators, and drying out. Depending on its development, the seed coat is either bitegmic or unitegmic. Bitegmic seeds form a testa from the outer integument and a tegmen from the inner integument while unitegmic seeds have only one integument. Usually, parts of the testa or tegmen form a hard protective mechanical layer. The mechanical layer may prevent water penetration and germination. Amongst the barriers may be the presence of lignified sclereids.

The outer integument has a number of layers, generally between four and eight organised into three layers: (a) outer epidermis, (b) outer pigmented zone of two to five layers containing tannin and starch, and (c) inner epidermis. The endotegmen is derived from the inner epidermis of the inner integument, the exotegmen from the outer surface of the inner integument. The endotesta is derived from the inner epidermis of the outer integument, and the outer layer of the testa from the outer surface of the outer integument is referred to as the exotesta. If the exotesta is also the mechanical layer, this is called an exotestal seed, but if the mechanical layer is the endotegmen, then the seed is endotestal. The exotesta may consist of one or more rows of cells that are elongated and pallisade like (e.g. Fabaceae), hence 'palisade exotesta'.

In addition to the three basic seed parts, some seeds have an appendage, an aril, a fleshy outgrowth of the funicle (funiculus), (as in yew and nutmeg) or an oily appendage, an elaiosome (as in Corydalis), or hairs (trichomes). In the latter example these hairs are the source of the textile crop cotton. Other seed appendages include the raphe (a ridge), wings, caruncles (a soft spongy outgrowth from the outer integument in the vicinity of the micropyle), spines, or tubercles.

A scar also may remain on the seed coat, called the hilum, where the seed was attached to the ovary wall by the funicle. Just below it is a small pore, representing the micropyle of the ovule.

Size and seed set
Seeds are very diverse in size. The dust-like orchid seeds are the smallest, with about one million seeds per gram; they are often embryonic seeds with immature embryos and no significant energy reserves. Orchids and a few other groups of plants are mycoheterotrophs which depend on mycorrhizal fungi for nutrition during germination and the early growth of the seedling. Some terrestrial orchid seedlings, in fact, spend the first few years of their lives deriving energy from the fungi and do not produce green leaves. At up to 55 pounds (25 kilograms) the largest seed is the coco de mer(Lodoicea maldivica). This indicates a 25 Billion fold difference in seed weight. Plants that produce smaller seeds can generate many more seeds per flower, while plants with larger seeds invest more resources into those seeds and normally produce fewer seeds. Small seeds are quicker to ripen and can be dispersed sooner, so autumn all blooming plants often have small seeds. Many annual plants produce great quantities of smaller seeds; this helps to ensure at least a few will end in a favorable place for growth. Herbaceous perennials and woody plants often have larger seeds; they can produce seeds over many years, and larger seeds have more energy reserves for germination and seedling growth and produce larger, more established seedlings after germination.

Functions
Seeds serve several functions for the plants that produce them. Key among these functions are nourishment of the embryo, dispersal to a new location, and dormancy during unfavorable conditions. Seeds fundamentally are means of reproduction, and most seeds are the product of sexual reproduction which produces a remixing of genetic material and phenotype variability on which natural selection acts. Plant seeds hold endophytic microorganisms that can perform various functions, the most important of which is protection against disease.

Embryo nourishment
Seeds protect and nourish the embryo or young plant. They usually give a seedling a faster start than a sporeling from a spore, because of the larger food reserves in the seed and the multicellularity of the enclosed embryo.

Dispersal
Unlike animals, plants are limited in their ability to seek out favorable conditions for life and growth. As a result, plants have evolved many ways to disperse their offspring by dispersing their seeds (see also vegetative reproduction). A seed must somehow "arrive" at a location and be there at a time favorable for germination and growth. When the fruits open and release their seeds in a regular way, it is called dehiscent, which is often distinctive for related groups of plants; these fruits include capsules, follicles, legumes, silicles and siliques. When fruits do not open and release their seeds in a regular fashion, they are called indehiscent, which include the fruits achenes, caryopses, nuts, samaras, and utricles.

By wind (anemochory)

 * Some seeds (e.g., pine) have a wing that aids in wind dispersal.
 * The dustlike seeds of orchids are carried efficiently by the wind.
 * Some seeds (e.g. milkweed, poplar) have hairs that aid in wind dispersal.

Other seeds are enclosed in fruit structures that aid wind dispersal in similar ways:
 * Dandelion achenes have hairs.
 * Maple samaras have two wings.

By water (hydrochory)

 * Some plants, such as Mucuna and Dioclea, produce buoyant seeds termed sea-beans or drift seeds because they float in rivers to the oceans and wash up on beaches.

By animals (zoochory)

 * Seeds (burrs) with barbs or hooks (e.g. acaena, burdock, dock) which attach to animal fur or feathers, and then drop off later.
 * Seeds with a fleshy covering (e.g. apple, cherry, juniper) are eaten by animals (birds, mammals, reptiles, fish) which then disperse these seeds in their droppings.
 * Seeds (nuts) are attractive long-term storable food resources for animals (e.g. acorns, hazelnut, walnut); the seeds are stored some distance from the parent plant, and some escape being eaten if the animal forgets them.

Myrmecochory is the dispersal of seeds by ants. Foraging ants disperse seeds which have appendages called elaiosomes (e.g. bloodroot, trilliums, acacias, and many species of Proteaceae). Elaiosomes are soft, fleshy structures that contain nutrients for animals that eat them. The ants carry such seeds back to their nest, where the elaiosomes are eaten. The remainder of the seed, which is hard and inedible to the ants, then germinates either within the nest or at a removal site where the seed has been discarded by the ants. This dispersal relationship is an example of mutualism, since the plants depend upon the ants to disperse seeds, while the ants depend upon the plants seeds for food. As a result, a drop in numbers of one partner can reduce success of the other. In South Africa, the Argentine ant (Linepithema humile) has invaded and displaced native species of ants. Unlike the native ant species, Argentine ants do not collect the seeds of Mimetes cucullatus or eat the elaiosomes. In areas where these ants have invaded, the numbers of Mimetes seedlings have dropped.

Dormancy
Seed dormancy has two main functions: the first is synchronizing germination with the optimal conditions for survival of the resulting seedling; the second is spreading germination of a batch of seeds over time so a catastrophe (e.g. late frosts, drought, herbivory) does not result in the death of all offspring of a plant (bet-hedging). Seed dormancy is defined as a seed failing to germinate under environmental conditions optimal for germination, normally when the environment is at a suitable temperature with proper soil moisture. This true dormancy or innate dormancy is therefore caused by conditions within the seed that prevent germination. Thus dormancy is a state of the seed, not of the environment. Induced dormancy, enforced dormancy or seed quiescence occurs when a seed fails to germinate because the external environmental conditions are inappropriate for germination, mostly in response to conditions being too dark or light, too cold or hot, or too dry.

Seed dormancy is not the same as seed persistence in the soil or on the plant, though even in scientific publications dormancy and persistence are often confused or used as synonyms.

Often, seed dormancy is divided into four major categories: exogenous; endogenous; combinational; and secondary. A more recent system distinguishes five classes: morphological, physiological, morphophysiological, physical, and combinational dormancy.

Exogenous dormancy is caused by conditions outside the embryo, including:
 * Physical dormancy or hard seed coats occurs when seeds are impermeable to water. At dormancy break, a specialized structure, the 'water gap', is disrupted in response to environmental cues, especially temperature, so water can enter the seed and germination can occur. Plant families where physical dormancy occurs include Anacardiaceae, Cannaceae, Convulvulaceae, Fabaceae and Malvaceae.
 * Chemical dormancy considers species that lack physiological dormancy, but where a chemical prevents germination. This chemical can be leached out of the seed by rainwater or snow melt or be deactivated somehow. Leaching of chemical inhibitors from the seed by rain water is often cited as an important cause of dormancy release in seeds of desert plants, but little evidence exists to support this claim.

Endogenous dormancy is caused by conditions within the embryo itself, including:
 * In morphological dormancy, germination is prevented due to morphological characteristics of the embryo. In some species, the embryo is just a mass of cells when seeds are dispersed; it is not differentiated. Before germination can take place, both differentiation and growth of the embryo have to occur. In other species, the embryo is differentiated but not fully grown (underdeveloped) at dispersal, and embryo growth up to a species specific length is required before germination can occur. Examples of plant families where morphological dormancy occurs are Apiaceae, Cycadaceae, Liliaceae, Magnoliaceae and Ranunculaceae.
 * Morphophysiological dormancy includes seeds with underdeveloped embryos, and also have physiological components to dormancy. These seeds, therefore, require a dormancy-breaking treatments, as well as a period of time to develop fully grown embryos. Plant families where morphophysiological dormancy occurs include Apiaceae, Aquifoliaceae, Liliaceae, Magnoliaceae, Papaveraceae and Ranunculaceae. Some plants with morphophysiological dormancy, such as Asarum or Trillium species, have multiple types of dormancy, one affects radicle (root) growth, while the other affects plumule (shoot) growth. The terms "double dormancy" and "two-year seeds" are used for species whose seeds need two years to complete germination or at least two winters and one summer. Dormancy of the radicle (seedling root) is broken during the first winter after dispersal while dormancy of the shoot bud is broken during the second winter.
 * Physiological dormancy means the embryo, due to physiological causes, cannot generate enough power to break through the seed coat, endosperm or other covering structures. Dormancy is typically broken at cool wet, warm wet, or warm dry conditions. Abscisic acid is usually the growth inhibitor in seeds, and its production can be affected by light.
 * Drying, in some plants, including a number of grasses and those from seasonally arid regions, is needed before they will germinate. The seeds are released, but need to have a lower moisture content before germination can begin. If the seeds remain moist after dispersal, germination can be delayed for many months or even years. Many herbaceous plants from temperate climate zones have physiological dormancy that disappears with drying of the seeds. Other species will germinate after dispersal only under very narrow temperature ranges, but as the seeds dry, they are able to germinate over a wider temperature range.
 * In seeds with combinational dormancy, the seed or fruit coat is impermeable to water and the embryo has physiological dormancy. Depending on the species, physical dormancy can be broken before or after physiological dormancy is broken.
 * Secondary dormancy* is caused by conditions after the seed has been dispersed and occurs in some seeds when nondormant seed is exposed to conditions that are not favorable to germination, very often high temperatures. The mechanisms of secondary dormancy are not yet fully understood, but might involve the loss of sensitivity in receptors in the plasma membrane.

The following types of seed dormancy do not involve seed dormancy, strictly speaking, as lack of germination is prevented by the environment, not by characteristics of the seed itself (see Germination):
 * Photodormancy or light sensitivity affects germination of some seeds. These photoblastic seeds need a period of darkness or light to germinate. In species with thin seed coats, light may be able to penetrate into the dormant embryo. The presence of light or the absence of light may trigger the germination process, inhibiting germination in some seeds buried too deeply or in others not buried in the soil.
 * Thermodormancy is seed sensitivity to heat or cold. Some seeds, including cocklebur and amaranth, germinate only at high temperatures (30 °C or 86 °F); many plants that have seeds that germinate in early to midsummer have thermodormancy, so germinate only when the soil temperature is warm. Other seeds need cool soils to germinate, while others, such as celery, are inhibited when soil temperatures are too warm. Often, thermodormancy requirements disappear as the seed ages or dries.

Not all seeds undergo a period of dormancy. Seeds of some mangroves are viviparous; they begin to germinate while still attached to the parent. The large, heavy root allows the seed to penetrate into the ground when it falls. Many garden plant seeds will germinate readily as soon as they have water and are warm enough; though their wild ancestors may have had dormancy, these cultivated plants lack it. After many generations of selective pressure by plant breeders and gardeners, dormancy has been selected out.

For annuals, seeds are a way for the species to survive dry or cold seasons. Ephemeral plants are usually annuals that can go from seed to seed in as few as six weeks.

Germination

Seed germination is a process by which a seed embryo develops into a seedling. It involves the reactivation of the metabolic pathways that lead to growth and the emergence of the radicle or seed root and plumule or shoot. The emergence of the seedling above the soil surface is the next phase of the plant's growth and is called seedling establishment.

Three fundamental conditions must exist before germination can occur. (1) The embryo must be alive, called seed viability. (2) Any dormancy requirements that prevent germination must be overcome. (3) The proper environmental conditions must exist for germination.

Far red light can prevent germination.

Seed viability is the ability of the embryo to germinate and is affected by a number of different conditions. Some plants do not produce seeds that have functional complete embryos, or the seed may have no embryo at all, often called empty seeds. Predators and pathogens can damage or kill the seed while it is still in the fruit or after it is dispersed. Environmental conditions like flooding or heat can kill the seed before or during germination. The age of the seed affects its health and germination ability: since the seed has a living embryo, over time cells die and cannot be replaced. Some seeds can live for a long time before germination, while others can only survive for a short period after dispersal before they die.

Seed vigor is a measure of the quality of seed, and involves the viability of the seed, the germination percentage, germination rate, and the strength of the seedlings produced.

The germination percentage is simply the proportion of seeds that germinate from all seeds subject to the right conditions for growth. The germination rate is the length of time it takes for the seeds to germinate. Germination percentages and rates are affected by seed viability, dormancy and environmental effects that impact on the seed and seedling. In agriculture and horticulture quality seeds have high viability, measured by germination percentage plus the rate of germination. This is given as a percent of germination over a certain amount of time, 90% germination in 20 days, for example. 'Dormancy' is covered above; many plants produce seeds with varying degrees of dormancy, and different seeds from the same fruit can have different degrees of dormancy. It's possible to have seeds with no dormancy if they are dispersed right away and do not dry (if the seeds dry they go into physiological dormancy). There is great variation amongst plants and a dormant seed is still a viable seed even though the germination rate might be very low.

Environmental conditions affecting seed germination include; water, oxygen, temperature and light.

Three distinct phases of seed germination occur: water imbibition; lag phase; and radicle emergence.

In order for the seed coat to split, the embryo must imbibe (soak up water), which causes it to swell, splitting the seed coat. However, the nature of the seed coat determines how rapidly water can penetrate and subsequently initiate germination. The rate of imbibition is dependent on the permeability of the seed coat, amount of water in the environment and the area of contact the seed has to the source of water. For some seeds, imbibing too much water too quickly can kill the seed. For some seeds, once water is imbibed the germination process cannot be stopped, and drying then becomes fatal. Other seeds can imbibe and lose water a few times without causing ill effects, but drying can cause secondary dormancy.

Repair of DNA damage
During seed dormancy, often associated with unpredictable and stressful environments, DNA damage accumulates as the seeds age. In rye seeds, the reduction of DNA integrity due to damage is associated with loss of seed viability during storage. Upon germination, seeds of Vicia faba undergo DNA repair. A plant DNA ligase that is involved in repair of single- and double-strand breaks during seed germination is an important determinant of seed longevity. Also, in Arabidopsis seeds, the activities of the DNA repair enzymes Poly ADP ribose polymerases (PARP) are likely needed for successful germination. Thus DNA damages that accumulate during dormancy appear to be a problem for seed survival, and the enzymatic repair of DNA damages during germination appears to be important for seed viability.

Inducing germination
A number of different strategies are used by gardeners and horticulturists to break seed dormancy.

Scarification allows water and gases to penetrate into the seed; it includes methods to physically break the hard seed coats or soften them by chemicals, such as soaking in hot water or poking holes in the seed with a pin or rubbing them on sandpaper or cracking with a press or hammer. Sometimes fruits are harvested while the seeds are still immature and the seed coat is not fully developed and sown right away before the seed coat become impermeable. Under natural conditions, seed coats are worn down by rodents chewing on the seed, the seeds rubbing against rocks (seeds are moved by the wind or water currents), by undergoing freezing and thawing of surface water, or passing through an animal's digestive tract. In the latter case, the seed coat protects the seed from digestion, while often weakening the seed coat such that the embryo is ready to sprout when it is deposited, along with a bit of fecal matter that acts as fertilizer, far from the parent plant. Microorganisms are often effective in breaking down hard seed coats and are sometimes used by people as a treatment; the seeds are stored in a moist warm sandy medium for several months under nonsterile conditions.

Stratification, also called moist-chilling, breaks down physiological dormancy, and involves the addition of moisture to the seeds so they absorb water, and they are then subjected to a period of moist chilling to after-ripen the embryo. Sowing in late summer and fall and allowing to overwinter under cool conditions is an effective way to stratify seeds; some seeds respond more favorably to periods of oscillating temperatures which are a part of the natural environment.

Leaching or the soaking in water removes chemical inhibitors in some seeds that prevent germination. Rain and melting snow naturally accomplish this task. For seeds planted in gardens, running water is best – if soaked in a container, 12 to 24 hours of soaking is sufficient. Soaking longer, especially in stagnant water, can result in oxygen starvation and seed death. Seeds with hard seed coats can be soaked in hot water to break open the impermeable cell layers that prevent water intake.

Other methods used to assist in the germination of seeds that have dormancy include prechilling, predrying, daily alternation of temperature, light exposure, potassium nitrate, the use of plant growth regulators, such as gibberellins, cytokinins, ethylene, thiourea, sodium hypochlorite, and others. Some seeds germinate best after a fire. For some seeds, fire cracks hard seed coats, while in others, chemical dormancy is broken in reaction to the presence of smoke. Liquid smoke is often used by gardeners to assist in the germination of these species.

Sterile seeds
Seeds may be sterile for few reasons: they may have been irradiated, unpollinated, cells lived past expectancy, or bred for the purpose.

Evolution and origin of seeds
The issue of the origin of seed plants remains unsolved. However, more and more data tends to place this origin in the middle Devonian. The description in 2004 of the proto-seed Runcaria heinzelinii in the Givetian of Belgium is an indication of that ancient origin of seed-plants. As with modern ferns, most land plants before this time reproduced by sending into the air spores that would land and become whole new plants.

Taxonomists have described early "true" seeds from the upper Devonian, which probably became the theater of their true first evolutionary radiation. With this radiation came an evolution of seed size, shape, dispersal and eventually the radiation of gymnosperms and angiosperms and monocotyledons and dicotyledons. Seed plants progressively became one of the major elements of nearly all ecosystems.

True to the seed
Also called growing true, refers to plants whose seed will yield the same type of plant as the original plant. Open pollinated plants, which include heirlooms, will almost always grow true to seed if another variety does not cross-pollinate them.

Seed microbiome
Seeds harbor a diverse microbial community. Most of these microorganisms are transmitted from the seed to the developing seedlings.

Seed market
In the United States farmers spent $22 billion on seeds in 2018, a 35 percent increase since 2010. DowDuPont and Monsanto account for 72 percent of corn and soybean seed sales in the U.S. with the average price of a bag of GMO corn seed is priced at $270.

Seed production
Seed production in natural plant populations varies widely from year to year in response to weather variables, insects and diseases, and internal cycles within the plants themselves. Over a 20-year period, for example, forests composed of loblolly pine and shortleaf pine produced from 0 to nearly 5.5 million sound pine seeds per hectare. Over this period, there were six bumper, five poor, and nine good seed crops, when evaluated for production of adequate seedlings for natural forest reproduction.

Edible seeds
Many seeds are edible and the majority of human calories comes from seeds, especially from cereals, legumes and nuts. Seeds also provide most cooking oils, many beverages and spices and some important food additives. In different seeds the seed embryo or the endosperm dominates and provides most of the nutrients. The storage proteins of the embryo and endosperm differ in their amino acid content and physical properties. For example, the gluten of wheat, important in providing the elastic property to bread dough is strictly an endosperm protein.

Seeds are used to propagate many crops such as cereals, legumes, forest trees, turfgrasses, and pasture grasses. Particularly in developing countries, a major constraint faced is the inadequacy of the marketing channels to get the seed to poor farmers. Thus the use of farmer-retained seed remains quite common.

Seeds are also eaten by animals (seed predation), and are also fed to livestock or provided as birdseed.

Poison and food safety
While some seeds are edible, others are harmful, poisonous or deadly. Plants and seeds often contain chemical compounds to discourage herbivores and seed predators. In some cases, these compounds simply taste bad (such as in mustard), but other compounds are toxic or break down into toxic compounds within the digestive system. Children, being smaller than adults, are more susceptible to poisoning by plants and seeds.

A deadly poison, ricin, comes from seeds of the castor bean. Reported lethal doses are anywhere from two to eight seeds, though only a few deaths have been reported when castor beans have been ingested by animals.

In addition, seeds containing amygdalin – apple, apricot, bitter almond, peach, plum, cherry, quince, and others – when consumed in sufficient amounts, may cause cyanide poisoning. Other seeds that contain poisons include annona, cotton, custard apple, datura, uncooked durian, golden chain, horse-chestnut, larkspur, locoweed, lychee, nectarine, rambutan, rosary pea, sour sop, sugar apple, wisteria, and yew. The seeds of the strychnine tree are also poisonous, containing the poison strychnine.

The seeds of many legumes, including the common bean (Phaseolus vulgaris), contain proteins called lectins which can cause gastric distress if the beans are eaten without cooking. The common bean and many others, including the soybean, also contain trypsin inhibitors which interfere with the action of the digestive enzyme trypsin. Normal cooking processes degrade lectins and trypsin inhibitors to harmless forms.

Other uses
Cotton fiber grows attached to cotton plant seeds. Other seed fibers are from kapok and milkweed.

Many important nonfood oils are extracted from seeds. Linseed oil is used in paints. Oil from jojoba and crambe are similar to whale oil.

Seeds are the source of some medicines including castor oil, tea tree oil and the quack cancer drug Laetrile.

Many seeds have been used as beads in necklaces and rosaries including Job's tears, Chinaberry, rosary pea, and castor bean. However, the latter three are also poisonous.

Other seed uses include:
 * Seeds once used as weights for balances.
 * Seeds used as toys by children, such as for the game Conkers.
 * Resin from Clusia rosea seeds used to caulk boats.
 * Nematicide from milkweed seeds.
 * Cottonseed meal used as animal feed and fertilizer.

Seed records

 * The oldest viable carbon-14-dated seed that has grown into a plant was a Judean date palm seed about 2,000 years old, recovered from excavations at Herod the Great's palace on Masada in Israel. It was germinated in 2005. (A reported regeneration of Silene stenophylla (narrow-leafed campion) from material preserved for 31,800 years in the Siberian permafrost was achieved using fruit tissue, not seed. )
 * The largest seed is produced by the coco de mer, or "double coconut palm", Lodoicea maldivica. The entire fruit may weigh up to 23 kilograms (50 pounds) and usually contains a single seed.
 * The smallest seeds are produced by epiphytic orchids. They are only 85 micrometers long, and weigh 0.81 micrograms. They have no endosperm and contain underdeveloped embryos.
 * The earliest fossil seeds are around 365 million years old from the Late Devonian of West Virginia. The seeds are preserved immature ovules of the plant Elkinsia polymorpha.

In religion
The Book of Genesis in the Old Testament begins with an explanation of how all plant forms began: "And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so. And the earth brought forth grass, and herb yielding seed after its kind, and the tree yielding fruit, whose seed was in itself, after its kind: and God saw that it was good. And the evening and the morning were the third day."

The Quran speaks of seed germination thus:

"It is Allah Who causeth the seed-grain and the date-stone to split and sprout. He causeth the living to issue from the dead, and He is the one to cause the dead to issue from the living. That is Allah: then how are ye deluded away from the truth?"

title: Seed