Lichen Basics

Day 106: This is the type of dry reading you're likely to see on official NPS pages from here on out, but at least it's science.

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Those of us who live in the Pacific Northwest are fortunate to have a wide variety of lichen species in our forests. Although lichens appear in almost every geographic region of North America, the leafier types are more abundant on the northwest and northeast coasts. Many of them are mistakenly called "mosses," but in fact they are complex symbiotic organisms. One of the most exciting revelations in the field of lichenology occurred this year when a third component was identified in the classic "fungus/algae" pairing: yeast. Let's look more closely at some common PNW lichens and learn a little of the specialized terminology which describes them.

There are three basic types of lichen: foliose, fruticose and crustose. Foliose ("FOH-lee-ose") lichens are "leafy" (think "foliage"). Platismatia (upper left) is an excellent example. Fruticose ("FROO-ti-cose") lichens are bushy or shrubby, or have a three-dimensional structure which often includes round stalks topped by cups or knobs. The photo in the upper right shows an example of Cladonia, a classic fruticose family.

Sometimes, it is difficult to assign a lichen to a specific category. The lower left image shows a Hypogymnia. The Hypogymnias are classified as "foliose-fruticose." The last type of lichen is called crustose ("CRUST-ose"), and as you might guess, it forms a crust which adheres tightly to trees and rocks. Crustose lichens often exhibit small fruiting bodies such as those which appear on Ochrolechia (lower right).