Learn About Leaves – Notes for teachers

General

All the leaf types in this worksheet can be found close to the lecture hut on Melville Koppies, so the group can stay quite close together – no straying into the veld!.

We have found that dividing the class into groups of about five works well. (It also will save on printing the pages with pictures). They should be warned about the Acacias; the thorns can be nasty, particularly the Acacia caffra which has sharp little “katdooring” thorns below the twigs.

There are two Acacias near the Lecture hut which are not indigenous to the Koppies, and have certainly been planted. They are the A. karroo which has long white thorns and reddish bark, and A. tortilis the Umbrella thorn, though ours looks nothing like an umbrella. This Acacia is very nasty because it has straight thorns and hook thorns, and not for nothing is it called a “haak en steek”

We have tried to keep a balance with technical terms. You may want to add or subtract. We have included a labeled diagram which you can download here.

We hinted at photosynthesis with the veins and the green colour of the Brachylaena, but decided to leave it out. The general photosynthesis equation is:

6CO₂ + 12H₂0 + sunlight 6O₂ + C₆H₁₂O₆ + 6H₂0

Carbon Dioxide Water Oxygen Carbohydrates Water

Names and Naming

We decided not to go into detail about the Linnean binomial naming system. (Linnaeus was working on his Systema Naturae from the 1740s.)

We were pedantic with the capitalization and italicization of the Genus species botanical names, but again decided not to make a big thing out of it.

There is an issue with the scientific names used here. The genus Rhus has been very recently divided on the basis of academic work done between 2001 and 2006, and all our Rhus species have been renamed Searsia.

This change has not reached the handbooks yet, but you will find it reflected on the SA National Biodiversity Institute website www.plantzafrica.com .

We decided to stay with Rhus, for the time being at least.

There is another change looming: scientists want to divide the genus Acacia, and it seems that the Australian Acacias will keep their names and ours will be put into another genus, possibly Senegalia.

You can read the official story at http://www.anbg.gov.au/cpbr/taxonomy/acacia-conserved-2004.html

The common names are taken from SAPPI Tree Spotting Highveld, (1998) Jacana, Johannesburg. This is an excellent popular guide with lots of information on common uses, good pictures and information on where the trees grow.

The exercise with the language and meanings of common names might be interesting, and if you get anything valuable you might share it with us.

We also left out any discussion of the meaning of the scientific names. Here are some notes which you might want to use:

“Rhus” comes from a Greek word meaning “red”. The most probable explanation in our view is that the wood when freshly cut turns a dark red. The SANBI site has a different view about the origin. Incidentally, while all members of the genus Rhus are trifoliate, not all trifoliates are Rhuses.

“Caffra” came into use quite early as a general word for “of Southern Africa” and is used quite often (Protea caffra for example – the Common Sugar Bush). It now rings a little uncomfortably, but no scientist has found the need to change it.

“The genus name Brachylaena is from the Greek brachus meaning short and klaina, a cloak.” (From SANBI site). This is a reference to the structure of the flower.

“Rotundata” refers to the shape of the leaf. Actually the leaf isn’t particularly round, but the name may have been given because a related species Brachylaena discolor has rather elongated leaves. “Discolor” refers to the green and grey colours of the leaf, and both species are equally “discolorous”.

“The genus name Celtis is the Latin name used by Pliny, and is also the ancient Greek name for one of the plants reputed to be the lotus of the ancients.” (From SANBI site).

“Acacia” may come from a Greek word “aka” meaning “point” – referring to the thorns. It is ironic that Australian Acacias have no thorns to speak of.

“Kiggelaria” is derived from the name of Franz Kiggelaer (1648-1722), a Dutch botanist and apothecary. Of course today you wouldn’t expect your local pharmacist to moonlight as a professional botanist, but the two disciplines were rather closer to one another in 1700.

“Robusta” is quite suitable as the leaves and leaflets are quite large and tough compared to other Acacias.

“leptodictya” from the Greek refers to the fine network of veins on the leaf.

“lancea” refers to the Roman auxiliaries' short javelin.

“karroo” is another interesting example of the quirks of botanical naming. “Karoo” is what we call the place – it would take an International Code of Botanical Nomenclature recommendation to change the name of the tree.

Editing and adding to the worksheet

If you modify the worksheet keep in mind that the pictures are embedded in text boxes and the text around them is made to fit by setting the left or right indent in the paragraph settings. The results could initially look messy if you add, move or remove material. The arrows may also go wild and end up pointing at nothing in particular.

SAPPI Tree Spotting Highveld will be very helpful to you and if you, the school library or even one of the kids buys a copy then we all win.

These web pages may be useful if you want to add information to the worksheet:

http://www.plantzafrica.com/plantklm/kiggelarafric.htm

http://www.plantzafrica.com/plantcd/celtisafrican.htm

http://www.plantzafrica.com/plantqrs/searsialancea.htm

http://www.plantzafrica.com/plantqrs/searsiapyroid.htm

http://www.plantzafrica.com/plantqrs/searsialepto.htm

http://www.plantzafrica.com/plantab/acaciacaffra.htm

If you want to go to extremes visit

http://www.bgbm.org/iapt/nomenclature/code/SaintLouis/0001ICSLContents.htm

We decided to stay away from the fact that Jacarandas and Black Wattle are category 3 and category 2 invaders respectively. You can pursue this topic at:

http://www.plantzafrica.com/miscell/aliens1.htm

If you have anything at all to say about this worksheet please say it at fomk@mk.org.za!