Lichen with Ruffled Skirts
Now that I recognize Parmotrema when I see it, I feel I’m encountering a friend. Sometimes I have an odd momentary feeling that it recognizes me also...
In the woods, I picked up a fallen branch. It was covered solid with lichens of many colors and shapes. The lichen in one spot was pale and had a ruffled skirt. I took it home to puzzle over its identity.
It’s called Ruffle Lichen.
Getting to know you…
The ruffled edge was one clue to who it was. Or rather to a bunch of related lichens, all of which are in the genus Parmotrema.
The top of a lichen, the part we usually see, is likely a different color from the underside, which is visible if we can pry up a bit of the edge and look at the other side. When a Parmotrema lichen is dry, the top looks whitish (photo above).
The underside is two toned. It’s dark in the center. Toward the edge is a white border, like contrasting trim on a petticoat (left photo, below).
Fed by the sun
This lichen is like a miniature loose-leaf lettuce. The leaves are thin and wavy. If we slice through the lichen and look at the cross section under a microscope, we see a fine line of green dots (middle photo, below).
The dots are tiny bundles of algae. The scientific term is photobiont (“foe-toe-buy-aunt”). The photobiont’s job is photosynthesis. It uses sunlight to transmute carbon dioxide and water into sugar. In rain, the top of the lichen becomes transparent. Sunlight pours through as if through a window and tickles the algae, which starts photosynthesizing like mad to make sugar. This is how the lichen gets nourished.
Within a minute of rain, the lichen looks bright green (right photo, above), because now we are seeing through the transparent surface and looking into the photobiont layer. Through a microscope, it appears splotchy, because we’re seeing the individual bundles of algae.
Clues to identity
Lichens are hard to identify, but every time I learn one I feel joy. Now that I recognize Parmotrema when I see it, I feel as if I’m encountering a friend. Sometimes I have an odd momentary feeling that it recognizes me also.
Here are a few tipoffs for Parmotrema.
The surface is fairly smooth, like linoleum. But when magnified, it shows fine cracks (left photo, above).
It has wide lobes, as lichens go. When I measured them, the lobes were about 4 mm wide (middle photo, above).
Through a 10-power magnifying glass, black hairs are visible along the lobe edges. Like eyelashes. These are called cilia. These are a feature of some members of this genus.
Put all those characteristics together, and yay! Parmotrema!
Why identify it at all?
Identifying lichens does not happen from a galloping horse. A person has to stop, look close, and know what to look for. Often we need a 10x hand lens to see the identifying details. But I’m an ordinary person without a laboratory or academic training in lichenology. For me, figuring out the genus leads my eye into really seeing the characteristics of the lichen and is satisfying. So I’m happy to know it is Parmotrema.
Knowing this Ruffle Lichen gives me an incentive to look at each tree as I walk past it, just in case my lichen buddy Parmotrema is ruffling there.
Diane, your posts about lichen are wonderful and make me look more carefully when I'm walking outside. I have a lot of lichen on old fruit trees and very old dogwood. I had assumed the lichen happens because the tree is old, like when I see lots of yellow bellied sapsucker holes. I don't see those on younger healthy trees. But now I'm noticing lichen on some pretty young redbuds. So maybe it's not related to the age of the tree?
I lichen yer Lichen! (Sorry for the pun, but I'm ....um...on the run!)