EN
Divergence angles were measured for inflorescences of Helianthus annuus with several hundreds to more than a thousand disk flowers. Quantitative analysis showed that the angles are robustly fixed in the vicinity of the ideal golden angle 137.508° as accurately as ~0.001°. The mean deviation from the ideal value varies for each sample. The results have important implications for phyllotaxis models, which are discussed by referring to a necessary modification proposed by Roberts.