About Selaginella willdenowii (Desv.) Baker
This species, Selaginella willdenowii, has blue iridescence on its leaves. The iridescence forms through thin-film interference in a thin layer of lamellar-structured cells located in the upper cuticle of the leaves. Researchers suggest this iridescence is an adaptation that lessens the impact of strong sunlight that filters through the forest canopy; without this adaptation, the strong light would damage this shade-adapted species. Blue iridescence is also seen in Selaginella uncinata, and both of these species are adapted to grow in the extreme shade beneath forest canopies.
