Forest Zombies

Day 83: This is how spooky stories begin: hands clawing up through the soil, wrinkled and darkened skin peeling back in shreds, yellow fingernails overgrown and seeking out victims. The Forest Zombies are coming to get you! You have to admit that the Peltigeras have a corner on "creepy" when it comes to their morphology, but the "fingernails" are in fact the apothecia (spore-producing structures) of these common lichens. Some "Pelts" are difficult to tell apart. Others, like Peltigera membranacea (Membranous Dog-lichen, above) are fairly easy, with naked-eye observation of the rhizines (root-like structures on the back of the lobes) being definitive. You should be able to tell it from any others, at least if you're brave enough to get close to a Forest Zombie.

Zombie Season

Day 3: Zombie season is at hand! Or maybe that should be "at fingernails." They're reaching up from the forest floor, from stumps, from rock crevices and logs. They're coming to get you, and they want to eat your brains! Yes, lichens of all sorts are celebrating the return of cool, wet weather, and Peltigera membranacea is no exception. One of the "pelt" lichens, its fruiting bodies (apothecia) look suspiciously like the tips of zombie fingers groping for an ankle from beyond the grave. Will you be dragged into their lair this Hallowe'en? Mind your step and don't go out after dark! They're waiting, waiting, waiting...

Peltigera Membranacea

Day 177: You might wonder (as did I) why Peltigera membranacea is referred to as a "dog-lichen." One source claims that it is because the rhizines resemble a dog's fangs. Whether this is accurate or not, I can't say, but it makes sense in a left-handed sort of way. The Peltigeras were once believed to be a remedy for rabies, based on what is known as the "doctrine of signatures," i.e., that herbs and plants having a similar appearance to a body part can be used to treat an affliction of that part. The resemblance of the rhizines to canine fangs suggested being bitten by a dog, therefore the lichen must have been useful against hydrophobia. Kids, don't try this at home! The "doctrine of signatures" is a myth, and a dangerous one at that.

So, that said, the "fangs" of Membraneous Dog-Lichen are the clue to its identity. Other lichens may share the same upper-surface characteristics, but only Peltigera membranacea has rhizines growing singly rather than in clusters or groups. This can be seen quite clearly in the righthand photo. These structures are often mistaken for roots, but their true function is to attach the lichen to its substrate. Many lichens have rhizines, although some can't be seen without a magnifier.

Peltigera Membranacea, Membranous Dog Lichen

Day 90: Although they resemble roots, rhizines such as those found on the undersides of Peltigera lichens, these non-vascular structures do not play a role in the lichens' uptake of nutrients. Rather, they are what attach it to its substrate material. They occur in many forms and sizes: hairlike, forked, branched, bottle-brush; short, long, dense, sparse and so on. The morphology of the rhizines is diagnostic in many foliose lichen genera, so a hand lens is a valuable tool to have in the field. In this instance, we have Peltigera membranacea, commonly known as Membranous Dog Lichen. Why "Dog?" The common name has always baffled me, so I turned to the internet for help with the mystery. According to Encyclopedia Britannica, it addresses the resemblance of the fruiting bodies to dogs' teeth. Personally, I think they look more like zombie fingernails.

Miniature Universe

Day 50: A friend maintains that I notice tiny things because I'm "built closer to the ground." He may have a point, although I'm inclined to think that although I grew taller, I never grew UP. I remember as a child being completely enraptured by a universe of little tree-like structures (the haircap moss shown above), but I do not recall lichens among my childhood discoveries. I can't imagine that they weren't present in the woods behind our house, but likewise, I'm sure my attention would have been drawn to them if they were there. Something like the "fingernails" of Peltigera membranacea wouldn't have been an item I could have overlooked, nor the pale blue-green forked branches of Cladonia squamosa. Unless I was sick, there wasn't a day I didn't have my nose to the forest floor in observation of some life-form. Yet somehow, I missed lichens. My life might have taken a different path if I had been introduced to them earlier. Oh, if only we could start over!

Rhizines

Day 200: Peltigera membranacea (Membranous Dog-Lichen) provides an excellent lesson in how lichens attach themselves to a substrate by means of root-like structures called rhizines which grow out from the back side of the thallus. In Peltigera, the rhizines are large and obvious; in the finely crustose lichens which occur on rock, they may be invisible without the aid of a hand-lens and yet if you were to try to peel one away, you'd soon discover why they are also referred to as "hold-fasts." Most lichenologists agree that rhizines do not assist in tranferring minerals or nutrients to the body of the lichen, although this has not been proven conclusively. Others suggest that close attachment to the host aids in retaining moisture.

Paired Pelts

Day 25: Lichens can be very selective as to their preferred habitat, but at this particular location, the dominant genus is Peltigera. But which species? That's been puzzling me for some time as I viewed them in a less-than-optimal state of dryness. I had thought the grey, crisp mass might hold both young and old specimens of a single species since there were subtle differences, but I was surprised when, after a good soak in our abundant October rains, two Pelts made themselves apparent. Peltigera britannica (left) is characterized by its bright green colour and dark cephalodia which are easily scraped off the surface of its lobes (a feature which distinguishes it from P. apthosa), and Peltigera membranacea (right) by its thin tissue and rope-like rhizines. These two colonies seem to be campaigning for dominance of the rock face on which they are growing. It's much more to my liking to ponder which will become the next President of Lichenopolis.

Plants Vs. Zombies

Day 128: When it comes to the Peltigeras (in this case, Peltigera membranacea, Membranous Dog-Lichen), it's like a game of Plants vs. Zombies where you can't tell who won. The strange brown "fingernails" exhibited by this species are its fruiting bodies (apothecia). The undersides of its greenish-brown foliose thallus attaches to the substrate with holdfasts called "rhizines," rootlike structures which can be seen in the upper and lower right corner of the photo. Just when you thought the forest was safe, now you find zombies reaching their fingers up through a carpet of moss, waiting to grab you by the ankles.

Peltigera Membranacea, Membranous Dog-Lichen

Day 60: In yesterday's post, I mentioned the rhizines which appear on the underside of Peltigera membranacea's "leaves" (the thallus). These brown structures are its apothecia, the fruiting bodies which produce the lichen's spores. Their resemblance to badly ingrown toenails is one of the defining characteristics of the species. Other Peltigeras produce similar apothecia at the tips of their lobes, but none is so markedly curled as that of Membranous Dog-Lichen. Why "dog?" I honestly don't know, unless it is because they are lightly furry. The Peltigeras are divided into two groups. "Dog-lichens" exhibit a tomentum (fuzziness) on the upper surface (refer to yesterday's glossary) and "Pelt lichens" which are either shiny or rough (scabrose). To further confuse matters, the Peltigeras are often referred to generically as "the Pelts."

Nesting Nidula

Day 59: One day I returned a little late to the office after a lunchtime walk and was explaining to Kevin that I had been sidetracked by a specimen of Hemitomes congestum while searching for Drosera rotundifolia, blathering on about the uniqueness of the find and the proliferation of mycoheterotrophic species I had been observing through the months of spring, only to have him say, "Crow, I have no idea what you're talking about." It pulled me up short and made me see that while I was throwing around botanical names and terms as casually as if I had been talking about Fred and George, most people are a bit uncomfortable with scientific jargon. I realize now that it might be easier on my readers if I provided a glossary, so let me give you one to accompany this photo of one of my favourite fungi, Nidula niveotomentosa, aka "Bird's-Nest Fungus."

Very often, the Latin name of a species will tell you something about its characteristics. In this case, "-tomentosa" refers to the presence of a tomentum, a velvety or woolly texture found on the surface of a plant. The view through the microscope at the top left shows this attribute...a fuzzy-wuzzy nest for the "eggs" which give this family of fungi its common name. The "eggs" (shown in the nest in the center 'scope view) are called peridioles. These contain spores. The bottom 'scope view shows the peridioles liberated from the "cup," appropriately called a peridium.

On the right, you can see the Bird's-Nests in situ alongside a flourishing colony of Peltigera membranacea, a member of the family of Pelt lichens. The translucent structures which appear like stalactites on the underside of the "leaf" are rhizines, a root-like structure which attaches the lichen to its substrate of rock, wood or soil. If you think fungus-jive is hard to wrap your tongue around, lichen terminology is another breed of cat. We'll get to that in future posts.

Pelt Rhizines

Day 85: While the discussion of pelt lichens is still fresh in my readers' minds, I thought another view of Membranous Dog-Lichen might be appreciated. If you thought their top sides were strange, this is what you would see if you turned one over. These threadlike structures are called rhizines, and they serve as roots to attach the lichen to wood or rock. Like any other root, the rhizines allow the organism to draw nutrients from the substrate.

Don't forget to stick a magnifier in your pocket the next time you go out for a nature walk! You never know what you might find.

Peltigera Membranacea, Membranous Dog-Lichen

Day 84: A member of the family of Peltigeras, Membranous Dog-Lichen is cousin to a number of species commonly found in the wet forests of the Pacific Northwest. All are characterized with apothecia which, to this observer at least, resemble distorted fingernails. These are the fruiting bodies of a lichen, generating spores when the organism reaches maturity. If you were to turn over the olive-brown "leaves" (technically, the foliose thallus), you would find their backs covered with thread-like "teeth" called rhizines. Closer investigation with a magnifying lens would reveal a velvety covering (tomentosum) on the upper surface of the thallus. The woolliness of the tomentosum can be used to distinguish Peltigera membranacea from Peltigera canina in the field (P. canina's is fuzzier). Membranous Dog-Lichen is one of the most common Peltigeras in northwestern forests.

Membranous Dog-Lichen, Peltigera Membranacea

Day 170: As if lichens weren't fascinating enough by themselves, existing only by cooperation between fungus and algae, their common names are utterly intriguing. Peltigera membranacea (Membranous Dog-Lichen) is a member of the larger family of "pelts," which includes among other Dog and Fan Lichens such oddities as Freckle Pelt, Frog Pelt, Carpet Pelt, and Born-Again Pelt. Other families have even more peculiar names: Rock Pimples, Ragbag, Sea-Storm, Spray Paint. Who thought up the vernacular nomenclature? And what had he been drinking? I can understand Oakmoss and Bearded Lichen, but what about Naked Kidney and Salty Rock Tripe? Gritty British Soldiers? Bloody Comma? It's enough to make me wonder whether my love affair with these complex lifeforms has its roots in science or etymology.