My friend Jennifer Hamilton found a perfect lichen in the woods, and she brought it to me. All green of earth circled by blue of sea, it is a Speckled Shield Lichen. Remarkably, it is complete and not broken.
It’s four inches (10 centimeters) in diameter. It wraps around the branch like a clasping hand. Unwrapped, it would be nearly circular.
The tree must have grown large while its passenger lichen expanded from a speck. Lichens of this type grow slowly, often only about one millimeter per year. Estimating from its dimensions, this lichen may be 50 years old.
In the center, green as grass
The center is of course the oldest part — it expanded from there. That part is green, completely covered with isidia. Isidia are reproductive structures, fine as dust, that contain the genetic stuff of the lichen. A microscope makes visible what the naked eye can’t see.
Every lichen is made up of at least two organisms in a partnership so intimate that they share one body. The greater mass of the partnership is a fungus, which cannot make its own food. Inside the lichen is something such as an alga that can make food, through photosynthesis, from sunlight, water, and air.
Magnified more, the isidia reveal themselves as rounded columns emerging from the body of the lichen.
The isidia can crumble off and float on a breeze. If they happen upon a good landing place, they become lichens and grow. Just give them time.
At the edge, blue as the sea
The edge of the lichen is the last part that grew. It does not yet have a coat of isidia, so we can see the bluish color of the body of the lichen (called the thallus). Through the microscope, details take shape.
White specks are minute breaks in the outer layer of the thallus, with the lichen’s white inner material peeking through. These white breaks are one of the main identifying characteristics of Punctelia lichens. Speckled Shield Lichen’s scientific name is Punctelia rudecta.
The survivor
When I saw Jennifer’s lichen, I felt a wave of admiration. This being has led a charmed life. Year after year, it slowly grew. No deer rubbed antlers against it. No hummingbird or gnatcatcher picked off lobes of lichen to camouflage a nest. No hiker slid the blade of their pocketknife under it, obliviously destroying half a century’s growth. Even when the branch died and fell, somehow the lichen remained whole.
Its path crossed mine, and I am grateful.
Thanks Jennifer! Also, thanks to Leland Searles and John Pearson, who identified it for me. This is a common lichen in eastern North America. It’s easy to find in woods and sometimes even in towns. There’s probably some growing near where you are right now.
I welcome comments (below), agreement or disagreement on the identification, or additional insights about this lichen.
I enjoyed reading the fascinating facts on lichens as well as the microscopic photos. Diane, I’m just curious as to what you will do with this precious gift? Can it keep living if placed in your’ woods? Nature is truly unfathomable❤️
I too am fascinated by lichens & most enjoy reading about your finds. Ours are a big different in the PNW, but all are amazing organisms