Cabinet of Curiosities

By guest contributor and collections volunteer, Jan Sharp. Have you ever walked down a trail in the woods and wondered, “What’s that white spot on the tree trunk?” or “What’s that gray-green stuff covering that dead tree limb?”  Most likely, what you’re seeing is a lichen – a symbiosis between a sac a fungus (an ascomycete), and a photosynthesizing algae or cyanobacteria. The fungus provides shelter and nutrients for the algae or cyanobacteria, which, in return, shares its sugars with the fungus. Lichens grow on rocks, tree bark and limbs, the ground, among mosses, and can even be found on rooftops.   This tree exhibits a healthy growth of Common Greenshield, among other lichens colonizing the bark's surface. Photo by Jan Sharp. Lichens have both beauty and function. They can form a thin crust on the bark of a tree or on a rock (crustose), often looking like a bird dropping. Lichens can also appear like a leafy mass (foliose) on a tree trunk or twig, or an alien-looking clus...