A lichen is not a single organism, but rather it is a combination of two organisms which live together intimately. Most of the lichen is composed of filaments of a fungus, but living among the filaments are algal cells, usually from a green alga or a cyanobacteriuim. The relationship between these two organisms, in which both benefit from the cooperation and neither is adversely affected, is called commensalism.
In many cases the fungus and the alga which together make the lichen may each be found living in nature without its partner, but many other lichens include a fungus which cannot survive on its own because it has become dependent on its algal partner for its survival. In all cases though, the appearance of the fungus in the lichen is quite different from its morphology when it is a separately growing individual.
I can’t say when my fascination with lichens began. It was so long ago that I cannot remember any particular event that awakened my interest; however, ever since my love of photography started, with a Kodak Brownie when I was eight or so, they have been one of the many natural subjects to which I have been drawn. In this new series, I’d like to present some of the lichens whose acquaintances I have made during my travels. There are a few dozen that I have chosen to include, so I’ll try breaking them down into groups according to where I found them. I’ve been paying a lot of attention to New Zealand recently, so I’ll save my lichenous treasures from there for future posts. For now, for a change, I believe I’ll start with several that I found in Finland.
(Note: Some of the information on lichens in my first two paragraphs was paraphrased from the website of the University of California at Berkeley, from a page entitled “Introduction to Lichens—an alliance between kingdoms.”)