You learn something everyday,
even at my advanced age!
lichen (li ken), n. an organism composed of a fungus
in union with an alga, commonly forming patches on rocks and trees.
What I didn't know was that "alga" is the singular of algae!
algae (al je), n.pl., sing. -ga (ge), any of numerous
one-celled or colonial organisms that contain chlorophyll
and usu. flourish in aquatic environments.
How about that?
Vail Point Park, St. Augustine.