In Robin Wall Kimmerer’s book Gathering Moss, she has a fascinating chapter about moss’s affinity for water. They lack roots to absorb water, so they have developed strategies to collect and retain water mostly from the rain but you will also find an abundance of moss in “spray zones of waterfalls and cliffs seeping with spring water.”
The shape of the leaves is important in the process of gathering water and holding onto it. Robin writes, “The microscopic surface of the leaf is sculpted to attract and hold a thin film of water. The leaves may be pleated into minute accordion folds that trap water in the crevices, undulations in the leaf creating a microtopography of rolling hills and water-filled valleys.”
While looking around at the arboretum, I came across this moss with wavy leaves that look like small rolling hills that run perpendicular to the length of the leaf. I am sure the accordion folds that Robin talks about can only be seen under a microscope, but I feel this moss achieves the same idea with larger undulations of its leaf structure.
Resource
Kimmerer, Robin Wall. Gathering Moss: A Natural and Cultural History of Mosses. 1st ed, Oregon State University Press, 2003.