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Afrikaans: Klipblom, Korsmors, Ligeen
German:
Fletchen Sepedi: Bolele Zulu: Phakama
Venda:
Vhulele
Do not touch.
Lichens
do not have stems, roots or leaves. The part that you can see
growing on rocks and trees is called the THALLUS (pluaral thalli)
1.
Upper cortex:
Under magnification, a section through a typical foliose lichen
thallus reveals four layers of interlaced fungal filaments. The
uppermost layer is formed by densely agglutinated fungal hyphae
building a protective outer layer called the
cortex, which can reach several hundred μm in thickness. Beneath
the upper cortex is an algal layer composed of algal cells embedded
in rather densely interwoven fungal hyphae.
2.
Algae layer: This part
makes up 5% of the plant. It provides food for the thallus (i.e.
photosynthesises) and is light loving.
3.
Fungal Hyphae: The fungal
part provides moisture and shelter, it is therefore the dominant
partner. The thallus consists of 95% fungi.
4.
Medulla:
Beneath this algal layer is a third layer of loosely interwoven
fungal hyphae without algal cells. This layer is called the medulla.
5.
Lower cortex:
Beneath the medulla, the bottom surface resembles the upper surface
and is called the
lower cortex, again
consisting of densely packed fungal hyphae. The lower cortex often
bears rootlike fungal structures known as
rhizines, which serve to
attach the thallus to the substrate on which it grows
EPILITHIC growth forms can be:-
CRUSTOSE
–
or “crusty” paint-like and flat are most commonly seen on
Buffelskloof Eco-Reserve. See the brightly coloured crusty coverings
on the rocks around you. They
are tightly attached to the surfaces on which they grow. They grow
very slowly, at a rate of about 0.4 to 3mm per year. Despite being
hardy, they can be destroyed if trampled on. It can take up to 100
years for to re-grow. This is one of the reasons why we request that
you keep to the designated pathways.
Top Left: Crustose lichen on bark. Top Right: Map lichen (Rhizocarpon
geographicum) on rock.
FOLIOSE
–
leaf like attach
themselves loosely to their substrates and can be seen on some of
the trees and rocks around you. A number of folios species occur in
the area. They grow faster than crustose lichens, at rates of up to
25mm per year. Various insect larvae spiders and mites use the
foliose lichens for food, shelter camouflage and to lay their eggs
under. Birds including the paradise flycatcher, use leafy lichens to
camouflage their nests.
FRUITICOSE
–
bushy or shrubby, e.g. Usnea or “old man’s beard”. The strap
shaped or hair-like lichens vary from minute 3cm long species to the
much larger 5m Usnea species which is often seen hanging from trees
around the escarpment. Fruticose lichens are the fastest growing af
all lichens species with growth rates of up to 150mm per year.
Left: Usnea australis,
a fruticose form, growing on a tree branch.
Right: Reddish-coloured lichen on volcanic rock in Craters of the Other forms also
exist: leprose
(powdery),
squamulose
(consisting of small scale-like structures, lacking a lower cortex)
and
gelatinous
(absorbs and retains water).
ECOLOGY
Lichens must compete with plants for access to sunlight, but because
of their small size and slow growth, they thrive in places where
higher plants have difficulty growing.
Lichens do not have roots and do not need to tap continuous
reservoirs of water like most plants, thus they can grow in
locations impossible for most plants, such as bare rock, sterile
soil or sand, and various artificial structures such as walls, roofs
and monuments. Lichens are active when wet and inactive when dry.
This means that in
Lichens, to
human beings, are often tasteless or extremely bitter. Their food
value, however, compares well with that of cereal crops. A delicacy
in
Lichens are vital in nature for:
-
Oxygen and carbon dioxide cycles
-
Soil formation
-
Food for certain animals.
They are also used in:
-
Perfumes
-
Traditional beers
-
Traditional medicines
-
Antibiotics
-
Preservation of mummies.
Toilet soap and perfumes are manufactured by the French.
Lichens are used medicinally:
-
Scandinavians use it as a substitute for penicillin.
-
- Germans use it to treat certain skin diseases.
- Xhosa use foliose lichen to remedy toothache.
Various lichen acids are used to fight certain plant mildew.
Also used in
Litmus paper used in chemistry – to determine if something is acid
or alkaline.
Lichen acids have been used as a natural wool dye for centuries in
lichens
indicate pollution:
This was shown in
Preservation
of mummies: The internal organs of the mummy were removed and the
empty cavity then packed with lichens, sawdust, brewer’s myrrh and
all sorts of spice. It is not known whether the Egyptians used the
lichen for its preservative or aromatic qualities or simply as a
light weight packing material which was highly absorbent.
BIOLOGICAL WEATHERING
Endolithic lichens loosen the grains of the rock they grow in. The
rocks break down to form new soil. As the rocks disintegrate,
minerals that have been looked into the rocks for hundreds of
millions of years are released. This is called the biological
weathering of rocks. It was found that endolithic lichen
(Lecidea sarcogynoides)
weathers sandstone at a rate of 1cm per 100 years.
There is a species of bagworms that uses loosened
quartz grains in rocks to build it’s bag. This bagworm species
contributes 5 tons of new sand to the ecosystem of the
Through this weathering process, endolithic
lichens give rise to the amazing landscapes and shapes one often
sees on weathered rocks.
Water, used by animals such as lizards, frogs and
insects accumulates in these little rock pools. Algae, fungi,
bacteria and various small animals also live in water, creating
small ecosystems. These pools eventually fill up with organic
material and sand so that plants can grow in them.
Approximately two thousand million years ago this
area was covered by a huge inland fresh water sea. Mud, sand and
other layers were deposited. The pressure of these layers on each
other and the drying effect of the sun changed the muds and sands
into the rocks that you see here today. Sand delta was transformed
into sandstone and quartzite. Muds were changed into mudstone and
shales, and where they contained bicarbonates, dolomites was
deposited.
DOLOMITE Dolomite is a greyish colour and very “wrinkled”.
The Afrikaans name for dolomite is elephant or old rock. Dolomites
are made up mainly of calcium magnesium carbonate, and so are
soluble to a limited degree. Weak carbonic acid (rain water)
dissolves away dolomites to form caves and sinkholes. The many caves
found in this area, including the Echo and Sudwana caves, bear
testimony to this. Dolomite contains the oldest known fossils –
stromatolites – which appear as home shapes in the rock and were
formed by algae growing on the floor of the sea.
Quartzite is the most common rock that you see
around you. It varies from grey to dark black and most of the rock
along the pathways is Black Reef Quartzite. Most of them are rough,
but where water has flowed over them, they are fairly smooth. Many
quartzites stand in small pillars with little “fairy landscapes” on
top of them. The cliffs in this area are quartzite.
Shale
is a soft rock and is often used in this area to make ashtrays and
carvings. The pathways are mostly made of shale. You will see that
many of the shales have ripples on them which indicate water flow.
Most of the smooth rolling hills in this area are formed by shales
and dolomites.
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