Lichen - Western Isles
Lichen - Western Isles Plants and Organisms . Lichens appear all over the Western isles, on rocks, on the ground, on trees, often they go unnoticed, however they are really amazingly pretty.
1700 Species of Locen in Great Britain
There are over 1700 species of lichen in Britain and quite a variety to be seen on The Isle of Lewis and Harris
Often the surfaces on which they are growing can be dated actually by the study of the lichen.
Many Lichens Live for Hundreds of Years
Some grow up to 6 metres in length whilst others may only grow a few millimetres in area. Many lichens can live for hundreds of years.
You will often see powdery masses on the lichens surface, in fact these are the tiny bits of the lichen body which will be shed to form new lichens. Each little bit will contain a combination of the fungal and the algal partner.
Many Lichens are Slow Growing
Many of the lichens grow relatively slowly, although this is dependant upon the actual species and also the environment around them and the medium they are actually growing on.
Lichen - What is LIchen?
The lichens arent a single organism like most other living things, they consist of two ( or sometimes more) partners that exist together, a fungus and an alga (or algae) , which produce a new body or lichen thallus.
Two Partners of Lichen Gain From the Alliance
The two partners each gain from their alliance. The alga produces nutrients by photosynthesis using the sunlight which assist in feeding both partners. The fungus creates the body in which they both live (the thallus).The fungus is unable to produce food so it relies on the algae to produce nutrients for both organisms by photosynthesis.
Lichens and The Environment
The lichens are very important as they help us to assess the health and the qualityy of the environment, they are very sensitive to air pollution. As some lichens grow extremely slowly, the information scientists glean can tell us about the history of he environment around the species a swell as how old the material under where they are growing (land - tree rock etc) is.
Often lichen use two methods of reproducing, that of sexual reproduction, which is by the production of spores or/and that of vegetative reproduction.
It seems though that it is quite complicated and vulnerable, at least the spore method is - as a spore has to relichenise, it must germinate in a location that is suitable and find an algal cell of an appropriate species in order to create a new lichen. Using the vegetative method, the proppagule already consists of both fungal and the algal partner and therefore it only has to stay put to start regrowth as a new lichen
Lichens in The Use of Harris Tweed
On the Isle of Harris, Lichens are the origin of the distinctive scent of older Harris Tweed.In the Western Isles, the slow-growing rock lichens were much-prized dyestuffs, and were used to particular effect in the Harris Tweed industry.
The generic term for these lichens is crotal, which was scraped from the rocks ( taking quite some amount of manual labour) and then was used to finish with a great variety of red and brown hues ready for the dying process.
Many other flowers and local plants were also used in the dyes to produce different colours, such as the tiny flowers of the tormentil, meadowsweet and sorrel, the water lily and the yellow flag irises which are so abundant here in The Western Isles.
Algal and Fungal Partners of Lichen
The Algal partner can combine with different fungal partners to create a different lichen. The fungal partner always forms the main body of the lichen. The fungus gives the visible, structural form. The funus also protects the algae from extremes of temperature and light
Categories of Lichen
Lichens are put broadly speaking into a few different groups or categories, depending upon their thallus (or main structure on the lichen). Some of the main ones are listed below. ( I hope to eventually acquire pictures of lichens from each category over time)
A) Foliose Lichens
These lichens have a flat , leaf like structure. Foliose lichens are often large with lobes that are leaf like and are usually attached to the substrate by rhizines. This type of lichen, the foliose lichen's name derives from the same root word as "foliage"
B) Fruticose lichens (Bearded Lichens)
These have an erect bushy structure and look very much like plants. Fruticose lichen are attached to the substrate at a single point. Frutose lichens stand upright or hang down. Frutose lichens also tend to have bright colours. Fruticose lichens ( known often as bearded lichen) have a branched, shrub-like thallus which is attached to the soil, plant or rock it is growing on by a sucker-like holdfast.
C) Squamulose lichens
These have a minut scale squamules. Squamulose lichens are crustose at the base and they have squamules that are leaf like at the outer margins. These very oftern can overlap and the result is a form of "mat" effect
D) Crustose lichens
These produce a flat crust on or beneath rock or tree surfaces. These arent able easily to be removed.
Dog Lichen - Peltigear Membranacea
One of the lichens to be seen here on the Western Isles is Dog Lichen which is a foliose lichen.
These lichens have a flat, leaf like structure. Foliose lichens are often large with lobes that are leaf like and are usually attached to the substrate by rhizines.
Name Derivation of Dog Lichen
This type of lichen, the foliose lichen's name derives from the same root word as "foliage
|Inches and cm sizes are approximate|