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Green-fingered maths

Dr Colin Bielby looks at organic ways to link maths and science for Science Week

If you had eight dried plant-pods - of peas, beans or even fast-cycling brassicas - and a length of string, could you find the average length of the pods? With a handful of such pods or some holly leaves, could you help children understand range, median and mode? Can you use a willow leaf as a non-standard measuring tool? Or could you measure time with a wild oat seed? These are just some of the experiments developed by Science and Plants for Schools (SAPS) to enhance children's understanding of maths through plant science, and vice versa.

Using rapid-cycling brassicas, pupils can grow "fast plants" that go through their life cycle, from seed to seed, in less than five weeks. This allows pupils to record, almost daily, the height of their own plant and its physiological changes as it matures.

There are also opportunities for counting and observing patterns by the dissection of a large model brassica flower into sepals, petals, stamens and carpels. The parts can be removed, displayed and discussed (see right). Comparing this model with other flowers reinforces the floral structure and involves appropriate mathematical exercises in number patterns.

Infants can study leaves, from willow, chestnut and holly trees for example. How tall are the children in willow leaves? Using leaves of different sizes and comparing results will help them realise the importance of standard units. Can they estimate the area of differently shaped leaves and put them in order of size? The leaf area can then be quite accurately obtained by using a one-squared centimetre acetate grid and coloured stickers. A comparison between their estimates and calculations often reveals quite unexpected results. Can they also prepare a prickly pictogram, using real holly leaves laid down in columns on the ground, on the basis of the numbers of prickles? From this they can prepare a tally chart, and the opportunity is there to introduce new terms such as median and mode - so number, shape and measurement are all covered.

For timing and angles, it is possible to use a wild oat seed with its attached awn - a hair or bristle that looks like a right-angled spike sticking out from the seed. In humid conditions this twists around, helping to bury the seed in the earth. The awn sometimes completes a circle of 360 degrees in less than a minute. With a little imagination this can be set up for measurement of time and angles (see above).

And how exactly do you find the average length of eight seed pods with a piece of string? Adding all the lengths and dividing by the sample size - in this case, eight - normally calculates this value. Laying the pods end to end is the equivalent of the addition but without the use of numbers. Place the string alongside the arranged pods and cut it so that it is equal in length. Fold the string in half (to give you the average length of four pods) then half again, and again. You now have a piece of string that is equivalent in length to the average pod. If you wish to incorporate exact measurements you can then use a ruler.

There has always been a clear link between mathematics and science. Children do not readily make cross-curricular connections, but you can marry science investigation with numeracy, mathematics and plants to create a real and relevant experience for pupils. Not only would this help to dispel the myth that plants are unexciting, it would also encourage pupils to collect and manipulate data and may even encourage more cross-fertilisation between maths and science lessons - a welcome reversal of the current trends in many primary schools.

For details about plant and mathematics primary workshops, contact Dr Colin Bielby, Institute of Education, Manchester Metropolitan University, Didsbury, M20 2RR (e-mail: C.Bielby@ SAPS website: For lesson ideas go to: www.saps. ac.ukinfoworksheets.html. An interactive plant life cycle website for primary pupils can be found at: lifecycle. This site lets pupils compare a plant grown in school with an animated cartoon and digital photographs. Measurements can be recorded on the site to produce a graph of the plant's growth. The author welcomes comments on this site.

10 steps to make a model brassica

You will need:

* 250ml plastic bottle with 6-dimple base

* 500ml plastic bottle

* Velcro

* 1 sheet A4 green card

* 5 sheets of A4 yellow card

* 3 ping-pong balls

* 6 granules of rice-starch-shape polystyrene packing granules

* 4 wire twists

* 1 cardboard tube

1. To make the pistil: cut a 250ml bottle, as shown by dotted line. Stick Velcro pads (hooked side) inside the bottle opposite the window. Stick hooked Velcro pads and strips on the base of the bottle as shown.

2. To make the ovules: stick a Velcro pad (fluffy side) on each of three ping-pong balls or 3-4cm diameter polystyrene spheres.

3. Make the stamens (four x 12cm, two x 6cm): to make the anther, take a rice-starch-shape polystyrene packing granule and attach to the "filament" - a pipe-cleaner with a Velcro pad (fluffy side) at one end. Stick them on to the hooked Velcro strips on the base of the pistil bottle.

4. To make the receptacle and pedicel: cut the top section from a 500ml plastic bottle. Stick three fluffy Velcro pads on the inside of the bottle to attach the pistil and stick four on the outside to attach the sepals.

5. Attach four 2cm x 1cm strips of fluffy Velcro pads for petals between the sepal pads, allowing strips to extend to bottle opening.

6. Stick the three ovules inside the pistil. Stick the six stamens on to the outside of the pistil.

7. Attach the completed pistil to the inside of the receptacle.

8. Prepare petals and sepals. Make them large enough to fit on A4 sheets of paper or card.

9. Attach the four petals, then the four sepals, to the outside of the receptacle.

10. Take a cardboard tube, 15cm long and of suitable diameter, and push the neck of the receptacle into the tube.

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