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).

Lecidea Lapicida, Grey-Orange Disk Lichen

Day 251: If you are a follower of my posts, you've heard me mention on several occasions that common names for many lichens must have been inspired by chemical substances having nothing to do with lichen composition. Here are a few drawn straight from Brodo: Pink-eyed Shingle, Blistered Script, Punctured Rock Tripe, Tar Jelly, Varnished Tube. I suspect there was more than one six-pack involved with those names, maybe a wee drap of single-malt or demon rum. This crustose species occurs on siliceous rock in exposed areas. Its rust-coloured thallus is quite eye-catching. Wouldn't you have thought that Lecidea lapicida deserved a more distinctive appellation than the grossly uninventive Grey-Orange Disk? "Burnt Chili" comes immediately to mind, or perhaps "Devil's Beauty Spots." No, they settled on Grey-Orange Disk instead. It must have been a really dull party.

Placopsis Gelida, Bullseye!

Day 177: Many crustose lichens are easy to overlook. At a glance, they might appear to be an inclusion in a rock face or a mineral deposit on the surface. For example, this specimen of Placopsis gelida (a "bullseye" lichen, ref. Vitt et al) could have been mistaken for a discoloured bit of quartz in a darker matrix when seen from a distance. Up close, the lichen reveals its complex form, brown cephalodia (wart-like structures) dotting the pale green thallus and darker lobes extending like fingers along its margins. Crustose lichens adhere tightly to their substrate material; it would be difficult to lift one of those tiny projections even with a pocket knife.