An activity you can use in the classroom
You can tell how humid it is by looking at pinecones.
In dry air, pinecones open their scales to disperse
seeds. In dampness and rain, they close them to protect
the seeds. In this activity, you will use pinecones
to create a hygrometer, a device that measures the moisture
content of the air. 
- Spray bottles
- Water
- Masking tape
- Box of toothpicks
- Small lumps of plasticine
- Pinecones (4 per group); preferably with scales
that are open, long, and relatively lightweight (These
cones are more sensitive to humidity than heavy, closed,
and woody cones.)
- Wide-mouth jars with lids (4 per group); the jars
must be taller than the pinecones.
- Divide your lump of plasticine
into four pieces; put one piece in each jar. Attach
the base of a pinecone to the plasticine at the bottom
of the jar.
- Use the spray bottle to
mist the pinecones inside the jars. Screw the lids
on tight, and turn the jars upside down. Monitor the
pinecones for the next several hours, writing your
observations on theworksheet.
- Once the cone has closed, open the jar. Leave all
the jars open over night. The next morning, record
your findings on the worksheet.
- When the cones are dry, fill one jar cap with water.
Turn the jar upside down and screw it onto the lid.
Be sure the cone does not touch the water. Leaving
the other jar cap dry, screw it on the jar. Seal both
with tape. These two jars serve as the control. Place
them in a cool, dark place.
- Repeat Step 4 with the remaining cones, but place
both jars in a sunny window. Observe and compare them
to the controls for the next four hours, recording
your observations on the worksheet.
- Can you find any other plants that respond clearly
to changes in humidity? List them on the worksheet.
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