The "Little World" of Lichen

Always fascinated with the idea of "little worlds" within the world that we humans occupy, I was examining a apple tree twig covered in a spring green-colored lichen recently. Lichen is everywhere, a fungus we find clinging to rocks and trees. In addition to the sage green flaky material coating the twig, there were interesting black spots that looked like little drums. I suspected they must be spores but really wanted to know what they looked like close up.  I work for a company that makes the most powerful microscopes there are - electron microscopes - so I thought I'd bring the twig into work and ask the scientists there if it would make for an interesting sample.  

A funny thing about the scanning electron microscope (SEM) is that you can look at a plain black piece of material at extremely high magnifications (5X as high as 1,000,000X for example) and see incredible details where there were none with the naked eye. Or you can look at something very curious, and put it in the microscope and it doesn't turn out to look like much at all at high magnification. 

Not so with the lichen. The images taken at different magnifications revealed the little world I suspected was in that green flaky material stuck to the dead twig.  At first the extreme close ups (in this case at 160X) were disorienting, but the scientist who took the images explained we were actually looking at the spores themselves, inside the dish-shaped, flat black area of the lichen - just one of the tiny little drum shapes called apothecia that appeared only in a few places on the twig.  Inside of that flat, dull black area of a single apothecium there are spores on stems just waiting to be released and start lichen life anew.

Looking from a little further away, (50X and 17X), the beauty of the whole colony of apothecia can be better appreciated. Of course with a scanning

electron microscope the images you can get are only in black and white, but they can be colorized in Photoshop.  And, as is the case with many biological specimens, the lichen is perfectly beautiful under the optical microscope that most of us are familiar with, and it is very colorful all by itself, even if it does look a little like frog warts.

Sometimes a closer look really can open up a whole new little world!   

Seated at the Scanning Electron Microscope.
My scientist coworkers: Vern Robertson, Dave Edwards,
and Breno Leite.

The lichen under the optical microscope. See the drums?