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Lichen Terminology

Lichens can be complex and difficult to identify without the first understanding the basic terminology. This page describes and illustrates the terminology used throughout the lichen trail. 

Substrate: the surface the lichen is attached to: can be rock, bark, cement signs, trees, or basically anything.

Apothecia: small cup shaped structures that are on top of lichen that release sexually produced spores. The gray crustose lichen below is covered in orange apothecia. 

 Lichen with orange apothecia

Soredia: Small, asexual reproductive structures. Soredia are small bundles of fungi and algae. These are found in several of the lichen on the trail. 

 Lichen Soridea Diagram

Pycnida: Small, structures that contain spores not associated with the apothecia. These structures vary widely in appearance, ranging from small black dots on the edge of the thallus to dark orange pimples as in Xanthomedoza fulva, as featured on this lichen trail and highlighted in the boxes below.

  Lichen classification by appearance

Lichen comes in all shapes, sizes, and colors. The most broad way lichenologist classify lichen is by growth patterns :crustose, foliose and fruticose. These growth forms have no relation to family, genus, species, or other scientific classification, it is simply apperance. 

Crustose is "crusted" on lichen. Some says it looks like the lichen was spray painted on to the substrate. The lower surface almost disappears into the substrate, making it impossible to remove the lichen from the substrate without destroying the lichen.  These are the most difficult of the three growth forms to identity, but provide extreme satisfaction once the crustose lichen is identified. 

Crustose lichen

Foliose lichen tend to look like leafy growths attached to the substrate with one or more stem like structures called rhizines. These can be removed from the substrate without damaging or destroying the lichen. This growth form is the most represented lichen on the lichen trail. 

Foliose lichen

Fruticose lichen is most ornate of the three growth types. These lichens can look like tiny trees, bushes, or even tiny pixie cups! While these are beautiful and unique, these growth forms are not commonly found on campus. 

Fructose Lichen

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Image Sources:



All other: Emma Runquist