Spirals of sunflower kernels

Inspired by
The Algorithmic Beauty Of Plants
Przemyslaw Prusinskiewicz, Aristid Lindenmayer
ISBN-13: 978-0-387-94676-4

The kernels of a sunflower appear to build a pattern of spirals.
Your eyes see spirals turning left and right.
The numbers of the left and right spirals are always neighboured Fibonacci numbers.
Mostly there are 21, 34, 54, 89 or even 144 spirals.
How many spirals your eyes see depends on the number of kernels.
New kernels (blossoms) appear in the middle of the sunflower and push the existing kernels to the outside.

'sunflower-playground.st' is the source code for the playground in Pharo Smalltalk using Roassal.
Just change the 'numberOfNodes' in the playground to get a new sunflower.
The resulting drawings show some spirals starting at the node labeled 0. Node 0 is always on the top and black.
With the increasing number of kernels your eye will identify different numbers of spirals.

So it's clear that a sunflower need not have to decide genetically how many spirals it should have.

BTW a pineapple has 8 and 13 spirals.