An important part of the author's theory of phyllotaxis (see the introduction to Part II) is the model of pattern generation presented in Chapter 6 and developed in Chapter 8. The model proposes an entropy-like function and is used to interpret the phenomenon of phyllotaxis functionally, in terms of its ultimate effect assumed to be the minimization of the entropy of plants. A principle of optimal design is used to discriminate among the phyllotactic spiral lattices represented by the control hierarchies. Every control hierarchy can be attributed a complexity X(T), a stability S(T), a rhythm w, and a cost Eb (a real-valued function defined on the set of hierarchies and called the bulk entropy). Algorithms derived from the model can be used to identify the spiral pattern giving minimal cost when a cycle of primordial initiation is completed (at Pr plastochrones). For example, the costs of the patterns <1,2>, 2<1,2>, and <3,4> are approximately equal to 1.08, 1.98, and 2.83, respectively. According to the model, the Fibonacci pattern is the most stable and the least complex, thus its overwhelming presence.

The model is developed for spiral patterns, but takes into account whorled patterns as well. It is used to generate the regular patterns and shows that multimery is a special case of multijugy. Whether spirality is primitive or not, the model supports the idea that the patterns must be modeled in an order comparable to their evolutionary order of appearance in nature. An evolutionary order has been sketched, going from Fibonacci patterns to normal and anomalous spiral patterns, and to alternating and superposed whorls. This model can be used to deal with the perturbed patterns (Section 8.6.3).