86 PART V The Part of Tens
to visualize the nuclei of cells. Place the coverslip on the slide and have
a look with your microscope using lowest magnification first. What
you can see is:
✔✔ Individual cells
✔✔The cell membrane surrounding the cells
✔✔The nucleus
✔✔Cytoplasm (which is the more or less liquid stuff inside the cells
and contains all the small structures cells need to survive)
Elodea
Elodea or waterweed is a genus of submerged aquatic plants used in aquariums.
You should be able to buy this from pet shops. Elodea canadensis is a species that
works best for this experiment because it has thin, straight leaves. But all other
species do their job as well.
You need:
✔✔A glass slide with coverslip
✔✔A dropper
✔✔An Elodea leaf
✔✔Water
✔✔Salt solution (2 teaspoons of salt in a cup of water)
Pick off an entire Elodea leaf and place it on the microscope slide. Add
a drop of water and observe the cell walls and the green chloroplasts.
If you add a drop of salt solution afterwards you can witness a process
called osmosis. The cells are shrinking because the salt forces the
intracellular water molecules to leave the cell. What you can see is:
✔✔ Individual cells
✔✔Cell wall surrounding the cells
✔✔Chloroplasts (the green plant structures in which photosynthesis
takes place)