Pinecones and phyllotactic form

The intersecting spirals on a pinecone invite a familiar story about Fibonacci numbers. The more interesting question is causal: what local developmental rules and physical constraints make those counts appear reliably without any part of the plant representing the sequence?

In the eventual simulation, frequency-domain representations may help measure regularity—but they cannot by themselves identify the developmental mechanism that produced it.

Questions this note must answer

• Which observations are explained by packing and which require a developmental model?
• How does the divergence angle arise, and how robust is it to perturbation?
• Where do reaction–diffusion explanations help, and where do mechanics dominate?
• Can a compact simulation reproduce not only the pattern but its failure modes?

This working outline will become a visual essay that separates mathematical description from biological mechanism.