Gliding fruits
Students’ Sheet
Introduction
Gliding is one way that the fruits and seeds of some plants
have adapted and evolved to improve their dispersion.
The Javan cucumber (Alsomitra macrocarpa) is a wonderful
example of a plant that produces fruit that releases seeds
capable of gliding vast distances. The plant grows in the
forests of Java, Indonesia. The fruits are about the size of a
football and each is packed with hundreds of winged seeds.
The seeds fall from the underside of the fruit and glide vast
distances.
A Javan cucumber fruit has:
 mass of 0.3g
A Javan cucumber fruit

a transparent wing with a span of 15cm

wing thickness of less than 0.01mm – less than 1/10th
the thickness of a sheet of paper
Other winged fruits and seeds rotate as they fall. Typically
they descend at about 100cm each second. But the shape
of the Javan cucumber fruit means that it descends at the
shallow angle of 12 degrees and falls only 40cm each
second.
A seed of the Javan cucumber
This seed inspired early aircraft wing design and its
aerodynamic properties have been researched.
Activities
Activity 1: Watching them glide
Watch the BBC video, narrated by David
Attenborough, in the article Vine seeds become 'giant
gliders'.
You could try finding other videos – just type ‘Javan
cucumber’ into your search engine.
Questions
1. Describe in your own words (a) a Javan cucumber
seed, (b) the flight of the Javan cucumber seed.
2. What happens when a Javan cucumber seed finally
reaches the ground?
http://news.bbc.co.uk/earth/hi/earth_
news/newsid_8391000/8391345.stm
3. How could you find the centre of mass of a Javan cucumber seed?
Science & Plants for Schools: www.saps.org.uk
Gliding Fruits: p. 1
Activity 2: Investigating aerodynamics
If you tried the activity Winged Fruits you probably found that the various shapes you cut from
paper fluttered, spun or spiralled (or sometimes a combination of these) to the floor.
If you look closely at pictures of a Javan cucumber seed you will see that the transparent wing
has a ridge at its leading edge. So let’s investigate the effect of making a paper strip with a thicker
leading edge.
Cut two pieces of paper:

12cm x 4cm

12cm x 7cm.
On the wider strip draw three lines 1cm apart from one edge.
4 cm
7 cm
1 cm
12 cm
Fold along the line nearest the edge, then again to the next line and finally a third fold. You
should now have a piece of paper that is 12 cm x 4 cm, with 3 cm that is one layer of paper and 1
cm that is four layers of paper. Use your thumb nail to make a good crease. The folded edge
tends to open up, so use a strip of sticky tape to hold it in place.
Paper strip X
one layer of paper
Paper strip Y
one layer of paper
four layers of paper
Compare the flights of

Paper strip X

Paper strip Y, with its leading edge folds on the top

Paper strip Y with its leading edge folds beneath
folds on top
hold this edge to launch
leading edge
folds beneath
In each case, hold each strip between your thumb and forefinger at the middle of the long side.
Hold at shoulder height and release by pushing it forward gently and letting the strip go almost
immediately.
Science & Plants for Schools: www.saps.org.uk
Gliding Fruits: p. 2
Questions
1. Describe the movement of paper strips X and Y when they were released (remember to try Y
with folds on the top and with the folds beneath).
2. Do strips X and Y have the same lines of reflective symmetry?
3. Both strips have the same mass, but what is the difference between the centre of mass of strip
X and the centre of mass of strip Y?
4. What have learned about the design of objects that might glide through the air?
5. Give reasons for the way the strips behave.
Note: The aerodynamics of flight are complicated, so don’t expect to be able to give a ‘right’
answer. Just think about gravity and about the arrangements and movement of particles in solids
and gases.
Activity 3: An origami Javan cucumber seed
Try to make a paper model of a Javan cucumber seed from a piece of paper 15 cm x 7.5 cm.
Step 1. Fold the paper
along the dotted lines as
shown below, crease it and
then open it out again.
Step 2. Fold up to the
crease and then fold again
long the original two fold
lines.
Step 3. Fold up the front of the seed and then
fold the tip of this back under the front.
Hold your paper seed folded side down and release it from shouder height.
It may glide perfectly first try. Don’t worry if it doesn’t – it just needs a little tweak!

If it tumbles gently to the ground, adjust the folds made in step 3 to move the seed’s centre of
mass a little nearer to the front.

If falls to the ground straightaway, adjust the folds made in step 3 to move the seed’s centre
of mass a little further from the front.
In either case the adjustments you make are likely to be small. Also, once you’ve made one
paper seed and worked out the diagrams, making another is much quicker. So keep on
experimenting.
Questions
1. The paper seed has one line of reflective symmetry. Where is it?
2. Estimate where the centre of mass is in the paper model (you could try to find its position
experimentally)
3. How do the model’s line of reflective symmetry and centre of mass compare with those of a
winged Javan cucumber seed?
Science & Plants for Schools: www.saps.org.uk
Gliding Fruits: p. 3