If the other fungi are nature's recyclers, lichens are nature's pioneers. Lichens find their homes in some of the most barren and inhospitable parts of the world. From there they slowly begin the process of creating a foundation for habitation by others.

Lichens (Mycophycophyta) are among the most fascinating organisms on this planet. Their very structure is unique: a symbioses of two organisms -- a fungus and algae -- so complete that they behave and look like an entirely new being. A lichen can literally eat stones, survive severe cold, and remain dormant for long periods without harm.

Lichens may well be the least well known branch of life. Common names, when available, typically apply to the entire genus rather than to indvidual species. Classification of lichens is undergoing change as well. In fact, Mycologists now suggest eliminating the Lichens as a Phylum and, instead, reclassifying each invidual lichen according to its fungal component -- typically Sac Fungi (Ascomycota). Never-the-less, lichens look so different from other fungi that they deserve separate treatment here.

Lichens can be divided into three basic forms: crustose, or crust-like; foliose or leaf-like; and fruticoseor stalked.

All lichens are believed to be edible (or at least not poisonous) except for Wolf Moss, shown below. Rock-tripe Lichens (not shown) are even considered a delicacy by the Japanese.

Crustose Lichens

Crustose lichens are flaky or crust-like. They can be found covering rocks, soil, bark, etc. -- often forming brilliantly colored streaks.

The yellow ones pictured here on a granite stone in the Rocky mountains, are probably Common Yolk Lichens (Acarospora spp.); the red, Caloplaca spp.; and green, Lecanora spp.. The little buttons to the left are a magnification of the red streaks above.

Foliose Lichens

Foliose (leaf-like) lichens can be papery thin or, in more advanced forms, netted branch-like. Branched foliose lichens have a distinct top and bottom surface, thus differentiating them from most fruticose lichens. This can be seen clearly in the Lung-like Lichen (Pseudocyphellaria anthraspis) photo, above left; the Puffed Shield Lichen (Hypogymnia imshaugii) on the right has a black undersurface.

The dainty mushrooms on the Lung-like Lichen are quite showy. If you look carefully of the Puffed Shield Lichen you will see that it too is fruiting with less conspicuous green funnel-shaped mushrooms.

Fruticose Lichens

Fruticose lichens are the most highly developed lichens. Their branches are much closer in form to "true" branches although, unlike most plants, the lichen branch has no specialized vascular system for transporting fluids.

The British Soldier Lichen (Cladonia macilenta), left, is one of the showiest fruiting lichens: even though the mushrooms are quite tiny, their bright color and distinctive form makes them stand out along the forest floor.

Old Man's Beard (Usnea spp., right and below) is a common green-grey lichen seen hanging from trees. A beginner may call all such lichens "Old Man's Beard" but, in fact, several look-alikes do exists (see below).

The fruiting Old Man's Beard (Usnea arizonica) below, right is another typical Usnea with a hairy appearance. If you look carefully at the lower right portion of the photo you will notice the wiry white inner pith of a broken branch. This is an identifying characteristic of all Usnea species: the inner cord becomes exposed when you grasp the ends of a branch and pull apart until it breaks.

Two similar-looking lichens are the yellow-orange Wolf Moss lichen (Letharia vulpina, below, left) -- named, oddly, because it was used to poison wolves -- and its bright green cousin Letharia columbiana (below, right) which graces the trees and floor of Montane conifer forests here in Northern California.

Lace Lichens (Ramalina menziesii, not pictured), can be seen hanging in thick curtains covering entire Oak trees with their flat lace-like growth.