Brown Lichen

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Brown Lichen

Post by MWP admin » Wed Nov 14, 2007 10:00 am

I am posting another specimen of what I think it is a lichen (though not 100% sure) It was found on a shaded large boulder in a rather moist habitat. Looks like a meteorite with alien growth :P Any info is greatly appreciated.

In the meantime, here is some good info about Lichens in general

http://en.wikipedia.org/wiki/Lichen
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Stephen Mifsud
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Post by D. Cilia » Wed Nov 14, 2007 10:59 pm

This could actually be inorganic calcite (CaCO3) crystal growth, I've seen this on museum samples and literature but never in Malta. Stalactites and stalagmites grow in a similar way. Is this particular spot sheltered from rain? Do you have any note of the texture of the growth?

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Post by MWP admin » Thu Nov 15, 2007 8:25 am

Interesting... Yes it was exposed to rain, and on its lower surface. I did not take a sample or not even touched it as I tought I should not disturb believing it was some rare lichen (and useless to take a sample since I do not know anything reg their ID)
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LICHEN.

Post by ROLCAM » Thu Nov 15, 2007 1:38 pm

Lichen, is an organism that consists of an alga and a fungus living as a single unit. The alga can make its own food with the help of sunlight. The fungus cannot make its own food, but it absorbs water rapidly.

There are about 20,000 species of lichens. Some grow on soil, but most grow on rocks or tree bark. Lichens live in many regions in which few plants can survive. Some species live in the extreme cold of the Arctic. Others live in deserts or on mountains.

Lichens have no roots. They have an outer layer of fungal cells that are pigmented green, brown, yellow, or gray. This protective layer, called the upper cortex, covers a zone of green or blue-green algal cells. Below the algal cells lies a food storage zone called the medulla and a further protective layer called the lower cortex. Most lichens have rhizines (fungal strands) that attach the undersurface of the lichen to the tree or rock.

Botanists recognize three groups of lichens. Fruticose lichens are shrublike and are attached only at the base to the substratum (surface on which they grow). Foliose lichens are leaflike in appearance. Crustose lichens are crustlike and are attached to the substratum by the whole undersurface.

How lichens grow. Because lichens have no roots, they grow only when moistened by dew or rain. When a moist lichen absorbs sunlight, the algal part produces sugar by photosynthesis (see PHOTOSYNTHESIS). Most sugar passes to the fungus, which uses it as food, thus enabling the entire organism to grow. Dry lichens do not grow, but they can survive extreme temperatures that kill moist lichens. Most lichens add about 0.1 inch (3 millimeters) a year to their radius, but a few species grow about 10 times as fast. Many crustose lichens grow only .01 inch (0.3 millimeter) yearly. In Arctic regions, these lichens may be as much as 4,000 years old.

Lichens reproduce in three ways. In most lichens, the fungus releases spores (microscopic cells) into the air. If a spore lands near a suitable alga, it grows around the alga and a new lichen is formed. Many lichens also reproduce by means of soredia. Soredia consist of several algal cells surrounded by a web of fungal strands. They form on the surface of a lichen and are carried away by wind or raindrops. If soredia get trapped in a crack of a tree or rock, they may begin to grow into new lichens. Some lichens produce isidia instead of soredia. Isidia are tiny, peg-shaped growths on the lichen's surface. Like soredia, they are broken off and distributed by wind and water.

The importance of lichens. Both animals and human beings benefit from lichens. In the Arctic, lichens cover much of the ground, providing winter food for reindeer and caribou. In other regions, many snails, slugs, and insects eat lichens. In the past, people used lichens as food during famines and as dyes or drugs.

Today, manufacturers use vast amounts of a lichen called oakmoss each year. Oakmoss is collected in Europe and North Africa for processing into a fixative for perfumes, after-shave lotions, and soaps. The fixative prevents flower fragrances from evaporating quickly. The Scandinavian countries export large quantities of a lichen known as reindeer moss. People in Germany and other central European countries make Christmas decorations from this lichen. Another lichen, called canary weed, is used to make litmus, a substance used to determine if a solution is an acid or a base (see LITMUS).

For more than 2,000 years, doctors have used drugs made from lichens to treat certain lung and skin disorders. During the mid-1900's, antibiotics were produced from lichens in Scandinavia, Germany, and the Soviet Union. These drugs are now made more economically from fungi.

Scientists use lichens to determine the amounts of certain pollutants in the air. Lichens die when exposed to sulfur dioxide, a poisonous gas that has many harmful effects. Thus, scientists can estimate the amount of sulfur dioxide in the air by observing the number and type of lichens growing at a particular site. Lichens also absorb metals. By analyzing lichens that grow near factories and smelters, scientists can determine the type of metallic pollutants released.

Scientific classification. Scientists traditionally have classified fungi in the plant kingdom, Plantae. Today, however, many biologists regard fungi as a separate kingdom, called Fungi. They classify lichens in the division Eumycota of this kingdom.
Roland Camilleri B.Ec. FCPA.

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Post by MWP admin » Thu Nov 15, 2007 9:51 pm

Thank you so much for the extensive info. I read the article with great interess. The pollution indicator property is fascinating, as is itself the tight symbiosis between the food producing alga and water capturing fungus.

I wonder how lichens are named since we are dealing with two organisms (Alga & fungus)

Thankd again for your effort in writing that long post
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Post by D. Cilia » Thu Nov 15, 2007 11:01 pm

I agree, great post.

As far as I know lichens are still named using the traditional Linnaean system because the two organisms are so closely dependent on one another that they do not exist separately in nature.

Interestingly, some botanists regard lichens as parasitic systems because fungal hyphae are often invasive towards the algae cells, penetrating them to extract the food produced from sunlight. But I think that's quite an 'extremist' point of view.

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LICHENS INDEX !!

Post by ROLCAM » Fri Nov 16, 2007 3:33 am

Hi, Stephen,

For your edification I would like you to have a look at this site:-

Lichen Index
Ethnographic literature is often very inconsistent in the names used for various
lichens. To attempt to reduce confusion, all lichens were named according ...
http://web.uvic.ca/~stucraw/lichenindex.html - 65k

bye for now.
Roland Camilleri B.Ec. FCPA.

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Post by MWP admin » Fri Nov 16, 2007 8:37 am

Interesting reference indeed - thanks for sharing
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