Although many lichens can be identified with nothing more than a 10X handlens, a student will have a much easier time with access to a few important tools and reagents.
Chemical Reagents
The secondary metabolites (chemicals) produced by lichens are commonly used to differentiate between species. Today, precise chemical compositions can be determined using HPLC (high-performance liquid chromatography) and TLC (thin-layer chromatography). However, for over one hundred years, lichenologists have used a few simple, readily available reagents to differentiate between lichens with different chemistries. By applying a small amount of each to the lichen using a capillary, and observing color changes (or performing a “spot test”), the presence or absence of certain chemicals can be determined. The recipes for these spot test solutions follow.
K reagent (KOH):
The “K” solution is 10% KOH (potassium hydroxide) in distilled/deionized water. Where KOH is not readily available, a similar solution of NaOH (sodium hydroxide–available at most hardware stores as drain opener) may be used with similar results. (Caution: both KOH and NaOH are caustic and may cause severe burns if used improperly–handle carefully!)
C reagent (NaClO):
The “C” solution is ~5% NaClO (sodium hypochlorite or “bleach”) in distilled/deionized water. Where pure sodium hypochlorite is unavailable, commercial bleach may be used (and usually comes pre-diluted at 5%). Again, handle carefully, as even household bleach may damage tissues!
P/PD reagent (p-phenylenediamine):
The “P” or “PD” reagent is made from para-phenylenediamine, a carcinogen. Generally, the best way to minimize exposure to the chemical and hazardous waste produced is to prepare the solution by taking one or two crystals of the chemical and dissolving them in absolute ethanol. This creates a very small amount of the solution. This method is also desirable because p-phenylenediamine is highly unstable in solution.
KC reagent:
The “KC” spot test is performed by placing a spot of KOH on the lichen, followed immediately by a spot of C.
Equipment
Most lichens can be identified with a 10X handlens. However, for viewing spores, a compound microscope is necessary. A sharp razor blade is also useful for sectioning lichens.
Sometimes, it may be useful to have a UV light to perform a “UV test” on a lichen. (Some lichens autofluoresce, some do not.)
Storing Lichens
Lichens are typically stored in packets made by folding acid-free paper width-wise about one third of the way up the page from the bottom. Each side is then folded in about one inch, and then the top is folded over the bottom of the packet. Most lichens can be placed inside one of these packets for long-term storage, and the packets can be labeled to indicate what is inside (see template below). It is sometimes nice to place some padding inside the packet, cheese cloth or cotton bandage wrap to protect the lichen. Larger specimens, or specimens remaining on rocks are often stored in small boxes.
Example Label (requires Adobe Reader)
LaTeX code used to create above herbarium label
For more information, refer to:
Brodo, I.M., S.D. Sharnoff, and S. Sharnoff (2001). Lichens of North America. Yale University Press.
McCune, B, and L. Geiser (1997). Macrolichens of the Pacific Northwest. Oregon State University Press.