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Natural Perspective

The Fungus Kingdom: Lichens

(Last modified: 15 July 1997)
[icon: crustose lichen] [icon: foliose lichen] [icon: fruticose lichen]

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 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 rank among the least well known forms 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 -- mostly 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

[photo: crustose lichen]

[icon: crustose lichen] 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

[photo: hypogymnia] [photo: lung lichen]
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 Pseudocyphellaria anthraspis photo, above left; the Hypogymnia imshaugii on the right has a puffed body with a black undersurface.

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

Fruticose Lichens

[photo: cladonia lichen] 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 in their forest habitat.
[photo: usnea lichen]

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.
[photo: usnea lichen]

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.
[photo: letharia lichen] [photo: alectoria lichen]

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


Annotated Bibliography

Alexopoulos, Constantine J., C. W. Mims, M. Blackwell, Introductory Mycology, (4th edition), John Wiley & Sons, New York, 1996

A college level text on the world of fungi, organized according to the principles of classification; includes information about classifying lichens.

Bland, John, Forests of Lilliput: The Realm of Mosses and Lichens, Prentice-Hall, Inc, New Jersey, 1971

A well-paced book describing the fascinating world of lichens and lower plants. The author discusses their structure, life, history, and uses in a very accessible manner. He even includes a basic identification guide at the end.

Hale, Mason E. and Mariette Cole, Lichens of California, University of California Press, 1988

A fairly technical field guide describing around 200 of California's 1,000 known lichens. The keys are supplemented with numerous black and white photos as well as color plates. The scientific names mentioned above came from this book.

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