Day 105: While it's actually quite easy to distinguish Evernia prunastri (top) from Hypogymnia inactiva (bottom) using only field characteristics, many lichens require reagent testing to achieve an accurate identification. Since some of the reagents commonly used have a shelf life of mere minutes, the amateur lichenologist is at something of a disadvantage. We often resort to placing "sp." ("species") at the end of the scientific name (as in "Hypogymnia sp.") when we are unable to test our specimens or narrow an identification down by location or substrate. That's "close enough for government work" when you don't have laboratory faciilities available.
