Lichens are not true organisms, but rather
represent a beneficial, symbiotic relationship between a species of fungi
and a species of algae. In almost all cases the fungus represents the
structural support and protective covering part of the relationship, and
the algae provides food for both through photosynthesis. The fungal compoment
is usually an ascomycete, but may also be a basidiomycete or a species
of the fungi imperfecti. The algae may be either a blue-green algae (a
member of the Monera related to bacteria) or a green algae. Scientists
suspect that this type of symbiotic relationship has arisen several times.
Lichens live in a variety of exposed habitats, such as on rocks, trees,
or open soil. Lichens are very important in breaking down exposed rock
and beginning the cyle turning rock into soil. Lichens are also important
indicators of changing environmental conditions and are currently used
to track the increase in "acid rain" because of increases in
the output of sulphur dioxide by humans. Lichens are characterized by
their external shape and structure. To learn more about lichens, visit
one or more of the excellent lichen sites listed below.
 Fun
with Lichens - Lichenland. Oregon State University. This is certainly
a great lichen site. You have two options; either non-technical or a more
advanced approach. In either case you query a database of lichen photographs
and information by choosing from a series of options based on structure,
life history, color, and so forth. You can find out about each of the
characters and structures of lichens by clicking on the picture associated
with each rather than making a choice. The result is one or more species
satisfying these characters and for each species there are both photographs
and information.
Natural
Prospective. The Fungus Kingdom: Lichens. Art Kornfeld. This page
is a tremendous, non-technical introduction to lichens with wonderful
photographs and information about the biology and structure of lichens.
Introduction
to Lichens. University California, Museum of Paleontology. An excellent
introduction to lichens with information about their life histories, ecology,
systematics, and morphology.
Lichens.
An excellent short introduction to lichens.
Lichens
of the Miller Springs Nature Center, Belton, Texas. Jerry Evans. This
site has two parts. The first is a general introduction to lichens covering
their structure, keys to lichen groups, collecting information, and general
information. The second half deals with so-called "Non-Crustose"
lichen species found on trees in the nature center with pictures and some
information about each.
Lichens
as Bioindicators. Global Lab, TERC. This site contains an introduction
to lichens and their role as indicators of detrimental environmental change
such as that caused by sulphur dioxide. It also contains classroom activities.
Checklists
of Lichens. T. Feuerer. Included with a series of lichen checklists
from around the world is a synonymical checklist of the lichens of North
America.
Identifying
North American Lichens: A Guide to the Literature. Philip F. May et
al. A very extensive source of published information, both paper and on
the web, on lichens in North America with particular emphasis on keys
and identification aids. The page is very large and will take some time
to download.
Lichens of the
Coppermine, Hood, and Thomsen Rivers, NWT, Canada. Photographs of
two species of arctic lichens.
Key
to Lichen Identification in New Hampshire. A key to lichen types in
New England.
Welcome
to the World of Lichenology. This site has links to other lichen sites
on the web and a gallery of lichen photographs.
North
American Lichen Checklist. Theodore Esslinger, North Dakota State
University. A checklist of the lichens of North America. The list contains
synonymy and a bibliography of lichen literature.
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