|Lichens add colour to a stone wall.|
Mostly, those splotches are lichens. And they’re actually pretty amazing.
To begin with, lichens aren’t one thing, but two. As the excellent guidebook Plants of Northern British Columbia puts it, lichens are fungi that have discovered agriculture. The basic structure of the lichen is provided by a fungus, a relative of mushrooms and puffballs. That structure is a kind of factory, filled with willing workers. Inside each fungus factory is a colony of algae, and that’s what creates the lichens’ sometimes-garish colours.
|Lichens on an ancient standing stone.|
Colour isn’t all the algae contribute. Safe inside their fungus, the algae work away at what they do best: converting sunlight into carbohydrates, vitamins, and proteins through photosynthesis, the same process plants use. The fungus, which can’t produce its own food, takes a share of what the algae produce as a kind of rent.
The arrangement works so well that the fungi and algae are inseparable, so they go under the single name of lichen. The kind of relationship the two partners have is called symbiotic, which means neither partner dominates the other and the arrangement benefits both of them.
The splotchy lichens (like the lichens on this ancient standing stone in northern Scotland) are just one form, called crustose or crust lichens. There are also lichens shaped like overlapping scales, and others shaped like curling dried leaves, miniature bushes, tiny clubs, or even fine hair. The floor of the boreal forest, which stretches across much of Canada, is so littered with lichens of all shapes and sizes that it’s sometimes called a lichen forest.
|Lichens in the Yukon forest.|
All those shapes, sizes, and colours have led to some pretty entertaining names. Spraypaint lichen, dog’s tongue lichen, chocolate chip lichen, and toad pelt are just a few. And there are plenty more. About 14,000 species of lichen have been identified so far, and there are still thousands more to find and describe.
Interested? Here are a few links:
A general online guide to lichens.
Ebook guide to lichens in Canada’s west coast forest.
Ebook guide to lichens in Canada’s mixed hardwood forests.
And for lots of information about lichens, as well as some beautiful photos, The Lichen Guide.