Microtome

Day 17: When preparing specimens for viewing through a compound microscope, tissue should be sliced as thinly as possible. This is extremely difficult to do by hand, although it is possible to obtain a workable section of soft material such as a lichen apothecium. A better solution is to use a microtome. The tissue is mounted in dental wax or paraffin if it is too small to be placed directly in the central chamber and then a slice is made with a straight razor to remove the end. By turning the dial at the base of the microtome, the mounted tissue can be advanced in 1-micron increments. With practice, it is possible to make cuts as thin as 1 micron. This will allow you to view the cellular structure of botanical specimens.

Here At Lichen Labs...

Day 1 of Year Six: Yes, I've decided to continue 365 Caws for another year if the Fates and Google will allow. Hard to believe I've been at this project for five years already. So, without further ado...

Here at Lichen Labs, we have entered a new phase in the tricky business of lichen identification, i.e., chemical testing. There are only a few qualifying reagents available to the home scientist, among them household bleach (the "C test") and caustic soda, aka lye (the "K test"). Both need to be handled with care to prevent chemical burns or degradation of materials from accidental contact.

To perform the tests, a small amount of reagent is applied to a specific section of lichen and then the tissue is examined under a microscope in order to observe any changes in colour. Even the simplest test can be useful in separating one genus from another, perhaps even one species from another. More sophisticated tests can be performed in a professional laboratory if one is available. Of course, a well-trained observer may be able to differentiate species by eye, but for the neophyte, a determination confirmed by chemical means is always best.