Afrikaans: Klipblom, Korsmors, Ligeen
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).
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
human beings, are often tasteless or extremely bitter. Their food
value, however, compares well with that of cereal crops.
Lichens are vital in nature for:
- Oxygen and carbon dioxide cycles
- Soil formation
- Food for certain animals.
They are also used in:
- Traditional beers
- Traditional medicines
- 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.
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 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.