A plant with no mate, money too heavy to move, and a note held for years

The plant was found in 1895 by John Medley Wood, curator of the Durban Botanic Garden, who came upon a single clump of four stems on a steep, south-facing slope of the oNgoye Forest in what is now KwaZulu-Natal, South Africa.[3] He searched the ground around it and found nothing else.[2] Cycads carry their sexes on separate plants, the way holly bushes do, so a lone male can no more set seed on its own than a bachelor can.[1]

Over the following years the wild plant was taken apart. Offsets were dug up and sent to gardens around the turn of the century, one of them reaching Kew, and in 1907 a collector carried two whole trunks back to Durban.[3] By 1912 a single stem was left on the slope, and in 1916 the forestry service removed even that, replanting it in a government garden in Pretoria where it later died.[5] Since then Encephalartos woodii has been extinct in the wild, a status the international conservation authorities record in the bluntest term they keep.[5]

Everything that survives is a clone. Because the species cannot pollinate itself and no female has ever turned up, every specimen is a graft or a sucker descended from that one Zululand plant, several hundred of them now standing in glasshouses and gardens from South Africa to England.[5] The oldest and most photographed grows at Kew, where it has been called the loneliest plant in the world, a single organism copied thousands of miles from home and unable to finish the one act that would let it carry on.[1]

Two long shots remain. Botanists have crossed the plant with its nearest relative, Encephalartos natalensis, and mean to breed the hybrids back toward the original over generations, hoping in the end to raise a female close enough to count.[1] The other hope is that a female is still out there. Since 2022 a team led by Laura Cinti at the University of Southampton has flown drones fitted with multispectral cameras and image-recognition software over the oNgoye Forest, training the system to pick a cycad's shape out of the canopy; they have covered only a fraction of the forest's ten thousand acres, and so far have found no mate.[4][2] The effort reaches past a single specimen, but its emblem is singular: a living thing kept going by human hands long after it lost the means to keep itself going.

The stones were never native to Yap. Yapese crews quarried them from limestone on Palau, an island some four hundred kilometres away, and hauled them home lashed to rafts and canoes across open ocean.[3] A rai's worth was never a matter of size alone. It rose with the labour and danger behind it, the skill of the carving, the names of its former owners, and above all whether anyone had drowned bringing it back, so that two stones of equal width could be worth wildly different amounts.[4]

The clearest illustration is a stone no one has ever seen. An American named William Henry Furness, who lived on Yap and wrote the first full account of its money in 1910, recorded a great rai that had slipped from a raft and sunk in deep water on the voyage home.[1] The crew swore to its size and quality, the island took them at their word, and the stone went on being owned and spent for generations while it lay on the seabed, as good as any disc standing in a village.[1]

That detail caught the eye of the economist Milton Friedman, who used Yap in 1991 to make a point about all money.[2] A stone on the sea floor and gold in a vault, he argued, work the same way, since what gives either its value is a shared and largely unquestioned belief about who holds the claim, a kind of public ledger kept in everyone's head.[2] He set the sunken rai beside an episode from 1932, when the Bank of France, wanting to turn dollars into gold, had clerks at the New York Federal Reserve move bullion into drawers labelled as French property; no gold left the building, yet the markets treated it as a real transfer and the consequences were real.[2]

The island had known a colonial version of the same trick. When German administrators, who had bought the Caroline Islands from Spain in 1899, could not get Yapese chiefs to repair the paths, they sent men to paint black crosses on the most valuable stones and declared them forfeit until the work was done; the roads were mended, the crosses wiped away, and the wealth handed back without a stone being lifted.[6] Several thousand rai still stand across Yap today, though a survey in 1929 counted more than twice as many before typhoons and a world war took their toll.[6][5] Everyday purchases now run on US dollars, but the stones still change hands for the things that carry the most weight, a marriage, a plot of land, a settlement between families, their ownership held in memory rather than on paper.[5] Economists reaching for a way to describe a currency with no coins and no vault tend to land on a comparison the islanders arrived at first: a rai is a balance in a ledger everyone can read, and the disc itself, like the figure in a bank account, is almost beside the point.[3]

The music began as a short piano piece by the American composer John Cage, written in 1985 and arranged for organ two years later, carrying the instruction that gives it its name: play it as slow as possible.[6] Cage, who died in 1992, left no hint of how slow that might be.[4] In 1997 a group of musicians, organ builders and philosophers meeting in Halberstadt seized on the obvious loophole. A person runs out of breath, but an organ fed by a bellows can hold a note for as long as there is air to push through it, in principle for centuries.[3]

They settled on a span of six hundred and thirty-nine years. The number came from the town's own history, since Halberstadt is home to what is often called the first organ built with the modern keyboard of twelve notes to the octave, dated to 1361, and the gap between that year and the year 2000 is 639.[3] The performance began a little late, on the fifth of September 2001, and it opened with silence, a rest that lasted about seventeen months before the first chord sounded in February 2003.[1]

There is no player. The piece runs on a purpose-built organ in the church of St Burchardi, its handful of pipes added one at a time as each new note falls due, and its keys held down by small sandbags so a chord can ring day and night for years without a human hand.[3] Air comes from electric blowers whose faint hiss is part of the sound, and in 2011 the instrument was enclosed in a case of clear acrylic to soften the volume for the building's caretakers.[4]

Because the notes change so rarely, each change has become an occasion. Pipes were added or stopped in 2011, 2012 and 2013, then nothing at all until September 2020, when the first change in some seven years drew a crowd and a live broadcast; further changes followed in 2022 and 2024, the last of them taking the sounding chord from six notes to seven.[5][4] The next change, which adds a further note, is due on the fifth of August.[2] The people who tend the project talk about it without much solemnity. Being German, its chairman Rainer Neugebauer has joked, they feel they must get it right in the end, though he reckons Cage, wherever he is, would only laugh at the mistakes they are bound to make across six centuries.[4] Almost no one now living will hear the last note, and that is rather the point: a piece of music built on the timescale of a cathedral, handed forward one rare note at a time to people not yet born.[6]