Eye-Catching Foliose Lichens

by Pat Jaquith
pat@westvalleynaturalists.org

Elegant Sunburst Lichen (Xanthoria elegans) 11.15.21

Brighter than the Blanket flower that grows nearby in summer, this rock-dwelling lichen is a long-time resident on this carbonate-rich rock. Exposed to the elements, temperatures that range more than 100 degrees, with no shade to protect it and no roots to find water, this lichen grows about .4mm per year. It has probably taken about 150 years to attain its current size. The following article describes some fascinating facts about this and some other foliose (leafy) lichens in our area.

Elegant Sunburst lichen gets its bright orange color from anthraquinone pigments in its cortex. The pigment is thought to protect the photobiont from damaging UV light, much as sunscreen protects our skin. The growth rate of this lichen was first calculated by its presence on a limestone gravestone with a known date of placement. Elegant Sunburst lichens are relatively abundant in our valley, thanks to the exposed lime-rich bedrock.

Stump among the reeds of Cliff Lake 12.03.21

I’ve looked at this artistically painted stump countless times, but only recently when the water had receded enough to get close, did I take a look with the hand lens and discover that the “paint” is a collection of foliose lichens!

Xanthoria is derived from Greek, meaning “yellow”. The bright green and orange pigments contain pulvinic acid. Even in December, these lichens have abundant reproductive apothecia – the orange round discs. In the lower picture, there are some silvery-gray strings of dead fungus. I was there a couple weeks later when there was a cap of snow/ice on the dead stumps, and the lichens seemed unchanged, despite the cold.

12.20.21
Xanthoparmelia cumberlandia 11.15.21

This foliose lichen is found on rocks; it looks like it could be painted on, but it has the leaf-like structures of foliose lichens; this species has a close look-alike that lacks the abundant brown apothecia of this variety. “Xantho-” comes from Greek meaning “yellow”; “Parmelia” comes from a Greek term meaning ‘fruit bowl’, probably a reference to the cupped fruiting bodies. Xanthoparmelia cumberlandia is a gray-ish green color when wet; it is silvery-gray when dry.

Frosted Rocktripe attaches to rocks with a “holdfast” that is thought to resemble a bellybutton. (Umbilicaria translates to “woolly belly button”). I once tried to pry one off, but “holdfast” located under that white wrinkled central area certainly deserved its name! The dusty-white top is constructed of physical structures that reflect light. The underside with its dense mat of black ball-tipped rhizines resembles the inside of a chimney, coated with soot. These lichens attach to vertical acidic rocks, seeming to favor the sheltered side.

Rocktripe has been cooked and used as food; it is not very nutritious for humans, but Musk ox and other animals eat it in winter. Humans usually regard it as starvation rations.

The term hyperborea comes from a Greek word meaning of the far north.

This Rocktripe species grows on many acidic rocks and rocky outcrops in this area. Usually, in their dry state, they look like a collection of crusty black leaves. When they are wet, round black apothecia (reproductive structures that remind me of knots made of string) may be sprinkled over the brown upper surface. The lower smooth black surface attaches to the substrate with a holdfast similar to that of the Frosted Rocktripe. This brown lichen contains the pigment melanin that is both protective from UV rays and absorbs light for warmth.

For more reading about lichens, these three articles on this website may be of interest: Flora, Fauna, Or…?; A Bouquet of Lichens, and Meet A Few Pelt Lichens.

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