  A simple model is presented which explains the occurrence of high order
Fibonacci number parastichies in asteracae flowers by two distinct steps. First
low order parastichies result from the fact that a new floret, at its
appearance is repelled by two former ones, then, in order to accommodate for
the increase of the radius, parastichies numbers have to evolve and can do it
only by applying the Fibonacci recurrence formula.
