84 PART V The Part of Tens
has to be bigger in diameter than your cork slice. Place the cork slice
on the slide right into the water droplet. Hold the coverslip at an angle
to the slide so that one edge of it touches the water drop. Carefully
lower the coverslip and ensure no air bubbles are trapped beneath it.
Place the slide on your microscope and view it using the lowest magnification,
first. What you can see are:
✔✔Rectangular cells
✔✔Cell walls surrounding the cells
Onion Tissue Cells
An onion is a perfect simple example to demonstrate the cellular structure of
plants and to investigate the most important cell organelles: cell wall, cytoplasm,
mitochondria (organelles for energy production), and the cell vacuole. And the
fresh raw material for this experiment is quite likely already in your kitchen.
You need:
✔✔An onion
✔✔A glass slide with coverslip
✔✔A sharp knife or razor blade
✔✔Tweezers
✔✔A pipette
✔✔Water
✔✔Methylene blue (optional, for staining)
✔✔Gloves (optional)
You know that thin membrane between the layers of an onion? This is
exactly what you need for your sample. First peel the onion and cut it
into four pieces. Remove one of the layers and peel off a piece of the
clear membrane from the inside layers with the tweezers. This is the
thin, transparent membrane in between the layers. Now, drop a few
drops of water onto the slide. Place the removed membrane flat on
the surface of the slide. The drop of water prevents the onion from
wilting and drying. If you have methylene blue, it’s now the time to