Concept

Model scope — where it appears

4 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
120° — a third of a turn3 and 6 — whorled137.51°2 and 3 — Fibonaccirise 0.055 in both panelsthe counts decide, not the eye

What a mechanism would have to show

This site says of every model it draws that reproducing a pattern is not explaining it. That is easy to repeat and hard to make precise. Here it is made precise — a list of what an account of phyllotaxis would have to establish, with each item marked according to whether the models on this site establish it.

mechanism · mechanism claims
upstream of the choicethe neighboursalready placedthe profileenergy by azimuththe choicethe least of itthe recordwhat a ruler readsjostle noiseplacement noiseone rule, three entry pointsthe order is the argument

A growing organ is part of the rule

Every model on this site places primordia on a surface and then treats the surface as furniture. But the surface grows between one placement and the next, and that growth reaches the rule through the only channel it has — where the neighbours are. What looks like a boundary condition turns out to be a term in the model.

mechanism · mechanism claims
00.2500.5000.7501012345distance from the candidate, in local spacingsweight the interaction is multiplied byhalf weightweight = f(d / 3√h)window runs to 4 widths

A neighbourhood is a hypothesis

Every simulation of this kind stops summing somewhere. The previous phase found that where it stops decides what pattern comes out — so the stopping place is not a detail of the program but a claim about how far a primordium's influence reaches, and it should be written down as one.

emergence · interaction range
204012345range at which the interaction has halved, in local spacingsnear-shell contrast — the first shell's variation over the second'swhat the exponent sweep leavesp = 1 · shells 0–2 and 2–4 spacingscontrasts 6% apart, ranges 47%

Two shapes, one threshold

Read in the same unit, an exponential falloff and a gaussian one disagree about where the lattice ends by half. The quantity they agree on turns out to be one the previous phase measured for an unrelated reason — and it agrees with a bracket left by a sweep of a completely different parameter.

emergence · falloff exponent

Named alongside it

The objects these essays reach for when they reach for this one.

The placement ruleRepulsionAuxinCut offThe range of the interactionLattice offsetNeighbourhoodPrimordiumRiseArtefactBasinCross validation

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