Two plants that merge into one, growing together to the benefit of each other. Sounds strange, but lichens are unique combinations of fungi and algae growing together, yet they are distinct from either of their components. They are abundant in nature, occurring just about everywhere: silvery gray flat patches growing on tree trunks, rocks, roofs and other flat surfaces. Well, most of the time that is what they are.

On occasion, they transform themselves into three-dimensional works of art. The strands of fungi expand away from the surface on which they grow, forming a vast network of feathery strands. I observed these transformed lichens last Jan. 14, while I was walking at Felix Neck Wildlife Sanctuary. From a distance the low shrubby-looking oaks adjacent to the green trail looked almost like they were in flower. Although it had been a mild winter to date, a closer inspection revealed that it was the lichens that were three-dimensional, standing up to two inches away from the bark of the trees.

Without the Internet at the moment (I am amazed how much I depend on it, even though I have used it for less than 10 years), my research today is limited to my own library, where I found remarkably little information about lichens. I found no records of such normally flat patches of growth transforming onto three-dimensional works of art.

My theory is that the air was so damp that the fungus had expanded and stretched outward to maximize the amount of water it could pull out of the air. The fog was so thick that the trees across the salt marsh were barely visible, and many branches had drops of water hanging under them even though it had not rained. There were no drops of water hanging from the lichen-covered branches because the lichens had absorbed it all.

Another observation of the relationship between moisture and lichens can be observed on our beaches, where they are one of the more abundant species growing in the back dunes. There is a large patch (maybe a quarter acre) of lichens on the Sengekontacket Pond side of State Beach, across from the Jabberwocky universal-access walkway. They are mostly one of the upright species (similar to the well-known British soldiers rather than the usually two-dimensional forms mentioned above), although they are only a couple of inches tall. In dry weather they are small and brittle, crunching underfoot when stepped on. But in storms and foggy weather they are very different, much more luxurious, even greenish in color.

Lichens are also survivors at the opposite end of the moisture extreme; they can survive in deserts because they enter a state of suspended animation when their water content is less than 10 per cent. The algae resume photosynthesis when water is restored.

General information about lichens is hard to come by. It is thought that there are about 17,000 species of lichens, mostly based on the structure of the fungi, which are unable to survive without their algal partners. The fungi provide the water and the minerals. The algae are inconspicuously embedded green cells that conduct photosynthesis to make their food.

There are three basic types of lichens — the flat crustose types and the small branched fruiticose types are both mentioned above. The third type is foliose, where the lobed margins of these leaf-like structures are often not attached to surfaces.

Identification of lichens is difficult, often requiring locating specialized structures with a hand lens or binocular microscope. Knowledge of technical terms like isidium, podetium, and squamules is essential, and could easily be the subject of another column or an entire book.

Robert Culbert is an ecological consultant living in Vineyard Haven.