Lichen It - Xanthoria parientina

We were walking in Myrtle Edwards Park on a Sunday afternoon and were struck by the vividness of this lichen, what we believe to be Xanthoria parientina. It was growing within 30-40 feet of the edge of Puget Sound on a deciduous tree in a sunny location. The little orange “cups” that stick up are called apothecia, the fruit body. Apparently, the more colorful Xanthoria is, the more it is producing sunscreen to protect the alga partner inside the lichen. You see, lichen is a partnership of two organisms living together: a fungus and a green alga or a cynobacterium or both. The lichen provides the house and the algae/cynobacterium provides food for the fungus. There is a nice page from the Natural History Museum about X. parientina.

X. parientina was originally name by our Linnaeus as Lichen parientinus. It can be found on page 1143 (page in Botanicus) of Species plantarum (1753) in the CRTYPTOGAMIA class (XXIV). The genus name comes from the Greek xanthos for yellow. The specific epithet parientina means “on walls”. A common name for this lichen is Golden Shield Lichen.

According to the Online Etymology Dictionary, the word lichen is described as: “c.1600, from Latin lichen, from Greek leichen, originally ‘what eats around itself,’ probably from leichein "to lick" (see lick). Originally used of liverwort; the modern sense first recorded 1715.”