Delaunay — where it appears
Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.
The six are the spirals
Label every contact between two cells in a seed head with the difference between the two nodes' placement indices. The labels are the parastichy numbers — 34, 55, 21, 89 — and the six sides Euler forces turn out to be about two from one family, one and a half from the next, and one each from two more.
Every family but two is a sum
A seed head has six spiral families and everybody reports two. That looks like a convention hiding information and it is the opposite — every family but the two smallest is the sum of two others, so a third count is a prediction rather than a measurement, and a check that catches a wrong pair.
Named alongside it
The objects these essays reach for when they reach for this one.
Golden angleLatticeLattice offsetMeasurementParastichyRational angleWhorledCounting blindCell areaContinued fractionContinued fraction convergentDisorder