Phyllotaxis
the spirals are counted, not admired
Series

Read window — the series

5 essays on one idea, from the one that introduces it to the one that assumes the rest.
  1. All 19 destinations, counted at 17 windows from 20 to 800 organs. One row per destination, one cell per counting window, coarsest on the left. A dark cell is a window returning the same pair as the standing 200; a warm cell is a window returning a different one; a pale cell is a window that reaches below the run's own settling organ and was dropped. 5 of the 19 rows differ anywhere, and every difference sits left of the floor its own pair sets — 20 organs for a pair under 14 parastichies and the larger count plus 6 above it. The census read at 25 organs and at 800 is the same census.

    The window nobody varied

    Every parastichy pair reported for the settling table was counted over the top two hundred organs of a run, and that number had never been moved. Moved seventeen ways across a factor of forty, on all three hundred and eighty-four settled runs, it changes nothing at all.

    part 1 · lattices
  2. What a 200-organ window allows against what the offset ceiling allows. Two settings decide what the counter can return, and at this window the offset ceiling is the tighter of them. A window of 200 organs holds a family of at most 194, since the counter scores an offset only where it has 6 hops of it inside the band; the largest offset it looks at is 60, a factor of 3.2 between them. The ticks are the members of the two sequences the essays are built on, and the largest counted number anywhere in the settling table is 19 — inside both bounds, which is what makes the table inert.

    A plateau the instrument should have had

    The counting window decides nothing on the settling table, and it has two bounds that decide everything outside it. A window one organ too narrow returns the previous rung of the same ladder, a family past the offset ceiling is reported as a coarser rung at every width there is, and neither failure produces a refusal, noise or a wide error bar.

    part 2 · lattices
  3. The window 16 known pairs need, against the 20 organs the counter refuses under. Cylinders built at a stated divergence and rise, counted at every window from 20 organs to 200, so the pair is known before the counter sees it. The smallest window that reads it is 20 organs for every pair up to 14 parastichies and the larger count plus 6 above that — 13 of 16 measured exactly, on both branches, with nothing fitted. A pair of 76 and 123 needs 129 organs where 2 and 3 needs 20; the open marks are pairs the counter's own offset ceiling refuses at every window, read only once that ceiling is raised.

    How many organs a pair needs

    A count taken over too few organs does not fail. It returns the rung below, which is a perfectly good pair, and nothing anywhere says so. The window that avoids it is not a constant but the counter's own arithmetic, and 384 settled runs sit exactly where that arithmetic puts them.

    part 3 · lattices
  4. The five readings of 384 whose two counted families wind the same way. Each row is an additive sequence with the term the counter stepped over drawn open between the two it returned. 4/9 is 1, 4, 5, 9, 14 with 5 skipped, and the pair a crossing requirement would have returned is 4/5 — a sequence the same destination's other runs already sit on. Dropping these readings takes the census at 40 starting angles from 31 arrangements and 15 sequences to 28 and 12, on 5 of 384 runs.

    A sequence that was a reading

    One of the settling table's additive sequences rested on a single count that skipped a term, and the account of it was that the count had been taken over the wrong patch. It was not. The counter works out whether its two families wind opposite ways and the reading throws the answer away, on five runs in three hundred and eighty-four.

    part 4 · lattices
  5. A stem at a rise of 0.003 unrolled, with each organ moved by 0.5 of a spacing. Two hundred and forty organs of an ideal lattice, azimuth across and height up, each moved in both directions by a gaussian with a standard deviation of 0.5 of the lattice's shortest vector. Open circles mark where each organ belonged, and lines join it to where it went. The pair 8/13 is the lattice's own.

    A wider window buys back a shaken stem

    On exact stems the counting window decides nothing once it clears a small floor, which leaves it looking like a setting nobody needs. Move every organ and it becomes the instrument. A pair that a twenty-organ window reads on an ideal lattice needs one or two hundred organs with each organ moved by half a spacing, four to eight hundred at four fifths, and up to twelve hundred at a whole spacing, where the organs have left their places altogether and the pair is still there to be counted. The price is steep, close to the two-and-a-half power of the error, and at one and a half spacings no window up to sixteen hundred organs holds the pair. When it goes, it goes upward: the wrong answer is the next pair, not the one below.

    part 5 · lattices

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