Tannins leached from leaves alter the surface behavior of water drops.

Evidence

Alder leaves lie fallen on the gravel, their drying edges upturned to form leafy cups. Rainwater has pooled in several, and it is stained red brown like tea from the tannins leached from the leaf. Strands of lichen lie scattered among them where the wind has torn them free. Suddenly I see the experiment I need to test my hypothesis; the materials are neatly laid out before me. I find two strands of lichen, equal in size and length, and blot them on my flannel shirt inside my raincoat. One strand I place in the leaf cup of red alder tea, the other I soak in a pool of pure rainwater. Slowly I lift them both up, side by side, and watch the droplets form at the ends of the strands. Sure enough, they are different. The plain water forms small, rapid drops that seem in a hurry to let go. But the droplets steeped in alder water grow large and heavy, and then hang for a long moment before gravity pulls them away. I feel the grin spreading over my face with the aha! moment. There are different kinds of drops, depending on the relationship between the water and the plant. — Robin Wall Kimmerer, Braiding Sweetgrass, 1099

Categorization

• XREF: Perfect concrete instance of ecology-as-relationship — the liquid’s identity depends on its contact with life — which echoes ch40’s carbon cycle and the river/island themes earlier.
• SHARE: An improvised natural experiment testing whether alder tannins change droplet behavior — appealing to anyone who loves field science and curiosity-driven method.