Mechanical model of the pattern formation of lotus receptacles

A two-dimensional mechanical model for pattern formation is described. The lotus receptacle is modelled as a ®nite circle packing with an elastic boundary of minimum length. The deformation process is controlled by an increase in internal pressure. Equilibrium con®gurations are sought. During the process, the con®guration is sometimes unchanged, sometimes changes continuously, but in some cases, by loss of stability, a dramatic rearrangement of the circles occurs. At the pressure under which the contact forces between circles vanish, the circles form a locally densest packing in a circle.