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Y for Yeti

#1632: the third Doctor Who said that there's nothing scarier than "a yeti on your loo in Tooting Bec". much of the yeti scenes were planned to be shot on the London Underground (James Chapman says the yetis have permanently changed the Piccadilly Line in the same way Psycho permanently changed motel showers) but to film in the actual stations, London Transport had strict rules. they gave up and built their own set, which was so good that LT sent them a letter asking when they managed to sneak down to film without them knowing! the yeti roar was someone flushing a toilet, slowed down a bunch. the costumes were meant to be even scarier, but it was often raining on set, and they had to dry out the costume with a hairdryer which made it look all "cuddly". they reused the costumes over several seasons, and by the end they were flea-infested and a little tatty....

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Y for Year

#1631: lunisolar calendars are so cool because they try to keep in touch with days, solar years AND lunar months! there's an average of 12.368 months in a year, and that little fraction is almost exactly equal to 7/19. in fact, this 19-year cycle is called the Metonic cycle (cool name! from the Greek who discovered it). lots of calendar systems use this cycle of 7 years with 13 months every 19 years: Babylonian, Athenian, Hebrew and Polynesian calendars all used it, possibly even independently. the date of Easter in the Christian calendar (and all the related movable feasts) is also based on a lunisolar system (the first Sunday after the first full moon after the March equinox). they invented a way to work it out for yourself based on some rudimentary maths and observations called computus paschalis, back in the 3rd Century when communications in the Roman Empire were falling apart and you couldn't rely on the Pope to tell you everything.

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Y for Years

#1630: it's unhelpful that a year isn't a whole number of days, or a whole number of lunar months. the biggest difference between modern calendars is how the leap years are distributed. the Julian calendar gets the points for simplicity (one leap year every 4) and only gains a day every 129 years - it would take over 47,000 years to loop back round. the Gregorian calendar has 97 leap years every 400 years, which puts it less than one part per million out - so it would take over a million years for that offset to loop round. some people have tried even better: the Revised Julian Calendar is about ten times more accurate than the Gregorian Calendar, with 218 leap years every 900 years. the last time the Revised Julian Calendar was exactly halfway out of sync, the genus Homo didn't exist, and Australopithecus roamed Africa.

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X for Xylem death (no way, cyclical narrative!)

#1629: xylem cells die much more quickly than most other cells. as usual, it's initiated by hormones like brassinosteroids and ethylene, which trigger the vacuole to begin swelling. the vacuole's membrane, called the tonoplast, changes material, until it suddenly explodes. once it does, the rest of the cell degrades very quickly, in a sort of everyone-for-themself kinda way. there are certain enzymes that hang around waiting for this to happen - Bifunctional Nuclease 1 and Zinnia Endonuclease 1 (cool names!), for example hang around in little pouches near the nucleus for much of its life, and quickly chop up any loose bits as it starts falling apart in its old age. then once the vacuole's exploded, these enzymes go to town on the whole nucleus. some other enzymes stick around even after the death of the xylem, we think as a form of anti-pathogen defence, because they're still useful for that.

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X for Xylem maturation (yes somehow still eking it out)

#1628: the secondary cell wall (SCW) in the xylem adds rigidity, strength, etc etc, but it also makes it difficult for stuff to get in and out the cell. which is fine for lots of cells, but the xylem need to distribute nutrients from the roots, so they have little indents in their SCWs to let water and nutrients transfer between cells. these pits are brought about by a protein called MICROTUBULE DEPLETION DOMAIN 1 (MIDD1) (yeah, all-caps, like some sort of Pokémon), which takes apart the teeny little tubules that make up the SCW. it begins by looking for the right place where it's needed, which is signalled by more proteins (blimey there's a lot of proteins) called Rac Small GTPases (known as ROPs by their friends). ROP11 recognises a specific pattern in the membrain and then summons the MIDD1 (just like Pokémon!). the MIDD1 binds to the ROP at one end and AtKINESIN13A (i choose you!) which dismantles the SCW like lego. all the different ROPs and MAPs (those proteins i mentioned at the end of the last fotd) work together to make sure the right ROP (ROP11, i assume) signals the MIDD1 in the right places, forming a regular pattern up the entire plant. i feel like i'm just spouting meaningless acronyms at this point, but trust me it gets so much worse. also, apparently, these pits are the biggest cause of embolisms but also the biggest preventative measure against embolisms in plants... not sure what to make of that

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X for Xylem maturation

#1627: when a xylem matures, it grows a secondary cell wall (SCW) which is exactly what it sounds like. the SCW needs to hold the lignin and cellulose fibres that give the plant rigidity, as well as offering more durability. it begins developing in a spiral shape round the inside of the cell (which is a cylinder, ish) and then "cables" are wrapped around before it's finished. (disclaimer before i carry on: take this all with a pinch of salt because i am way out of my depth...) a ladder forms between the cables and moves up and down, filling in the rest of the SCW. the climbing proteins know exactly when to stop, to make the best pattern of SCW - this is an area of ongoing research, but they've recently found five classes of proteins that are associated with the tiny little tubes inside the cell walls, probably got something to do with this.

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X for Xylem development (how many facts can we squeeze out of the one interesting X-word?)

#1626: as well as an autoregulatory positive loop, vascular auxins also go through several other feedback loops at the same time. the auxin originates in procambial cells and then travels to the protoxylem via the PIN (which doesn't really stand for anything - it's a little helper protein that moves stuff between cells). the auxin then goes through a bunch of stages with more unintelligible acronyms, to induce cytokinin, which in turn promotes procambium growth, leading to more auxins. there's another intermediate stage called AHP6 (again, don't know what it stands for) that in turn inhibits the signalling of cytokinin in the protoxylem. i think they've shown that this means that cytokinin has an inhibiting role in protoxylem growth, but they're not sure why (altho i'm not sure if that's up-to-date).

but - there's another! a mutually inhibitory interaction loop between cytokinin and auxin (basically, the two things cause less of each other) that has something to do with the proliferation of specifically PIN1 and PIN7, which means that auxin can transfer at a higher rate, which means that it speeds up the inhibition cycle - except just right, such that it dictates the shape of the protoxylem in the roots. i think. i'm sure there are more loops i'm missing - this is all inordinately complicated.

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X for Xylem growth

#1625: the hormone auxin is responsible for most growth in plants, and xylem is no exception - except auxin is transported in the xylem. there's a fun little loop where auxin promotes xylem growth such that auxin can use the xylem to get to more xylem to promote more xylem. this happens right from the get-go as an embryo, happening simultaneously across the plant (at this stage the plant is usually all still underground, but it's beginning to distinguish the root and not-root). the auxin also promotes specification of the protoxylem cells into xylem cells, which i guess are slightly different between root and stem?

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X for Xylem

#1624: the vessels in the root of a plant begin out quite differently but end up ultimately quite similar to those in the stem: the xylem begin as an axis across the middle of the root (well, we're talking about the cross-section, so really it's more of a plane, but wevs). there are two bundles of phloem perpendicular to the xylem band (a bit like a ÷). just like the stem, a change in the type of meristematic tissue (procambium -> cambium) triggers secondary growth that fills in the gaps, but first there has to be a a lot more (pro)cambium tissue between the xylem and phloem, else it just leaves too much of a gap. in leaves, there is usually not secondary growth at all. the same bundles of xylem-procambium-phloem as in stems appear in the leaves, in neat rows with the xylem facing upwards. because needles last ages (up to 33 years on some common species), there is secondary growth of phloem (only) here, but usually just to replace dying phloem.

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X for Xylem and phloem

#1623: there are two tissues that form the xylem and phloem inside a plant (like the equivalent of veins and arteries): the procambium and cambium. the procambium is just a meristem, ie stem cells that can produce cells of any variety, and they form little bundles of phloem and xylem, with the phloem forming towards the outer edge (rimwards, in Discworld terminology) and xylem towards the middle (hubwards). this is all called the primary growth of a stem, forming the first round of vessels. then, the procambium also produces cambium tissue which is slightly more specialised: cork cambium sits on the outer surface, producing bark; vascular cambium continues doing the same process of producing bundles of xylem and phloem; between these bundles, interfascicular cambium also appears to fill in the gaps. this is secondary growth, and gives us things like wood, tree trunks, etc - it's at this point that lignin properly appears.

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W for Whistle-stop tour

#1622: a whistle-stop used to be kind of like a modern request stop on a railway - a train would only stop at a whistle-stop if it was told to by the stationmaster. i've seen it explained that the whistle was given by the stationmaster to the train engineer (as if to say "stop please") but also the other way round (as if to say "we're coming; should we stop?") so if anyone knows how that used to work let me know...... thus, a whistle-stop tour was a tour of small stations where a train normally wouldn't stop. politicians used to go on all sorts of whistle-stop tours; for example, Harry Truman gave speeches at over 250 small towns (by my count) in a two-month trip in 1948, in the Ferdinand Magellan Pullman railcar. occasionally these still happen - Ronald Reagan, then-prince Charles, and Biden all did actual whistle-stop tours. Angela Merkel did one in the train of Konrad Adenauer.

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W for Writing on the Wall

#1621: Belshazzar was a Babylonian king in the 6th Century. modern scholars think his claim to the dynasty could've been a bit of a lie, but more importantly, he rejected the greatness of God and blasphemed. a disembodied hand appears and writes on the wall: מנא מנא תקל ופרסין . (i'm scared the RTL is gonna mess up the formatting...) and they need to pull in Daniel, the only guy in Babylon who can read Hebrew apparently. Hebrew doesn't spell out the vowels so Daniel actually needed to pull his weight here. (the first two words repeat) he turned the three words into mənê, təqêl and p̄arsîn, three monetary values of the time. but he turned these words then into verbs by keeping the same stems (the consonants), and they translate to "number" (your days are numbered), "weigh" (you're judged), "divide" (your kingdom will be divided). there was also a wordplay in there somehow: the root for p̄arsîn/pərês/pārās also gives the word for "Persian", meaning the kingdom is divided between the Medes and the Persians. i'm not sure what happened to that bit because Belshazzar died that night and his kingdom went to Darius the Mede (who we can't actually verify existed anyway).

anyway, reading Hebrew at the time required skill, hence why "being able to read the writing on the wall" (an idiom for being able to predict and accept failure) is difficult. this is in fact where we get the phrase "writing on the wall" (not Harry Potter or something...)

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W for Wild Bongo

#1620: after his almost-two-term presidency, Theodore Roosevelt wanted to get out of the way of his successor, Taft, but still stay in the headlines - so he and his son Kermit went hunting in British Africa. they hunted up and down the continent, killing things we'd rather have back, like white rhinos and no fewer than 18 lions, all in the name of science (and fame). but the headline target of their hunt was a beast called the bongo, "which no white man has ever seen". the bongo is in fact a stripey antelope, quite pretty but wholely harmless. they eventually did kill one, and the newspapers were initially confused because "bongo" was at the time primarily a people in South Sudan, and they thought, that's pretty dark, even for Kermit. they eventually clarified, and newspapers reported "KERMIT HAS KILLED A WHAT IS IT" and "OH JOY!". there was a lot of cynicism though - a rhyme spoofing on Yankee Doodle, jokes about "a carnivorous little animal that puts in all its spare time rhyming with Congo", one paper had "a private wire to the effect that a Bongo is a species of pocket gopher". by the end of 1910, the word "Bongo" had become a joke, not an animal. only one source i can find actually thought, hm, maybe killing isn't a good idea, and even then, hinging on the fact that Kermit killed a female and her young.

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W for Wikiquette

#1619: Wikiquette, the etiquette of Wikipedia, is on the whole pretty sensible: be friendly, don't attack personally, stay calm, etc.. what interests me, though, is the forms of "you" that different languages make, when they have that distinction. for those that don't know, many languages distinguish between a "formal" and "informal" version of the second person pronoun. English used to do this too: "you" was originally formal of "thou" (which is also why verbs conjugate to "you" as they do with plurals: "you are" is like "they are" whereas it'd be "thou art"). the homepages of the French, Russian and Turkish Wikipedias all use the formal pronoun (vous, вы and siz) but German uses the informal form (du). those are all the ones where i know enough about the language to recognise pronouns... the German Wikipedia has an interesting page outlining exactly why they use "du" (there's a word in German meaning "to use du": duzen). to summarise, it's tradition - when Wikipedia started, it was a small group of people, who all duzen each other.

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W for Welsh rarebit

#1618: (for those who don't know, Welsh rarebit is like cheese melted on toast with mustard or Worcestershire sauce, like a nicer version of grilled cheese.) unsurprisingly, "rarebit" comes from "rabbit", not the other way round. that's why there's "buck rarebit" topped with an egg (a buck is a male rabbit), or a "blushing bunny" with tomato. Welsh rarebit/rabbit doesn't come from Wales as far as we can tell, but the name is a bit of a mean joke, saying that the Welsh can't afford meat. sometimes they distinguish between other types of rarebits - English rarebit, for example, by soaking the bread in wine beforehand. there are lots of other pejorative food names in English: Welsh caviar is laverbread (seaweed bread - this one's actually Welsh), Scotch woodcock is scrambled eggs on toast with anchovies (actually sounds nicer than a woodcock), and Irish apricot is potato. a "Welsh comb" is just running your fingers through your hair.

if anyone can tell me what an "Oxford hare" is that'd be grand lol

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W for Welwitschia

#1617: is a plant with just two leaves. ever. it grows its first leaves after it's grown its cotyledons (just after germinating), and then never grows any more leaves. the two leaves just get bigger and bigger. there's a little woody stem in the middle but nothing much else. it can get reeaally old, so sometimes the leaves begin shredding in the harsh Namib desert (oh yeah it lives in the desert) and it looks like it has a few long leaves but really those are just one long leaf. it can get so old (and also it doesn't grow rings or anything... because the stem never gets any bigger) that the only feasible way to test how old one is is with radiocarbon dating. yeah, the same method that calculated the end of the last ice age measures the age of a single Welwitschia plant. its Afrikaans name sums it up pretty well: tweeblaarkanniedood 'two leaves; can't die)

it's also known as the tumbo, which i think comes from a local name (not sure what language....) but someone else (Joseph Hooker) wanted to name it after the first European to discovered it, Friedrich Welwitsch

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W for Warts and all

#1616: Cicero (aka Tully) was a Roman orator and politician. like most famous Romans, he was best known by his cognomen, which is a nickname that became hereditary, and was used to identify branches within a family. thus most cognomens were initially slightly nonserious - Caesar's ancestor may have been born by C-section, for example (see fotd#1437). as for cicero - that comes from the Latin word for chickpea, so one of his ancestors allegedly had a wart on his nose and got bullied so hard that his descendants for centuries to come bore the grunt. a 15th century Elector of Brandenburg was also named Cicero, after Tully, which may not have been the most flattering choice. there are lots of similar cognomens - "Fabius" (bean), "Lentulus" (lentil), "Piso" (pea) probably all come from warts too, and were incredibly popular. Cicero had a sister-in-law called Fabia!