Directional scattering from the glossy flower of Ranunculus: how the buttercup lights up your chin.

The bright and glossy appearance of the flowers of Ranunculus repens was investigated spectroscopically and the optical results were correlated with the layered anatomy of the petal. The highly directional reflected light arises from the partially transparent, pigment-bearing epidermal layer, while a more diffused yellow colour is the result of scattering from the lower starch layer. This directionality of the light reflections causes the unusually intense gloss of the buttercup flower and the strong yellow reflection evident when holding the flower under the chin.