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Nature Notes
by Bob Thomas

Lichens are abundant in coastal Louisiana, as they are throughout other ecological regions of Planet Earth.

Lichens exist in many forms, ranging from flat, smooth organisms to frilly species and those that resemble greenish Spanish moss (which, of course, is a flowering bromeliad and not a moss).

Lichens are biologically interesting in that they are composed of symbiotic associations of fungi (called the mycobionts) and algae or cyanobacteria (the photobionts, the latter being blue-green algae). The fungus gives the organism its structure and a means of maintaining moisture, and the algae or cyanobacteria supply the fungus with nutrients.

Lichen species are defined by the type of fungus, type of photobiont, and the shape the association assumes. Though some are distinct enough that they can be identified by their morphology, a lichenologist often has to apply certain chemicals to note color changes in order to distinguish among species.

A characteristic lichen of coastal Louisiana, and one easy to identify by amateur naturalists, is the Christmas (or Christmas wreath) lichen, Cryptothecia rubrocincta.

It gets its common name from its color pattern, consisting of a red fringe (the prothallus) around the body of the lichen (the thallus), which itself ranges in color from pale to mint green. “Rubrocincta” translates to “red wreath.” The central, oldest area of the thallus is often adorned by dense clusters of small red granules that look somewhat like isidia – one of the two types of reproductive methods employed by lichens.

However, absolutely nothing is known of this lichen’s reproductive techniques or cycle.

Christmas lichens are normally found growing on the sides of trees, especially in rather thin bottomland hardwoods (especially on oaks) and swamps (on cypress) where they get good sunlight.

In the U.S., Christmas lichen is a natural history beauty that interests only naturalists, but in Brazil it has been used to make a red dye.

Also published in Delta Journal, The Times Picayune, January 13, 2008.


Christmas wreath lichen, Cryptothecia rubrocincta,                        A cypress tree heavily infested with wreath
growing on a tree along the Coquille Trail in Jean                          lichen. Photo taken along the Jean Lafitte
Lafitte National Park.                                                                  Nature Trail, Lafitte, LA, July 29, 2008.
Photo by Bob Thomas.                                                              Photo by Bob Thomas.

Christmas wreath lichens also grow in large
patches on trunks along the Coquille Trail at
Jean Lafitte National Park.
Photo by Bob Thomas.