90 PART V The Part of Tens
✔✔Sugar
✔✔A Petri dish or glass slide with coverslip
✔✔A dropper or pipette
Put the yeast together with warm water and two tablespoons of sugar
in a bowl and stir it. Let the solution sit for 45 minutes. Place a drop of
this mixture on a glass slide, cover it with the coverslip and observe it
with your microscope. To visualize yeast cells, you need higher mag-
nifications. What you can see is:
✔✔Yeast cells (which are more or less round-shaped)
✔✔Reproducing (budding) yeast cells
✔✔Gas bubbles (carbon dioxide) that yeasts produce during the fermentation
of sugar
Potato Starch
Potato starch grains are birefringent. To visualize the structures, you need a
light microscope that is equipped with polarization contrast and/or darkfield illumination.
You need:
✔✔A potato
✔✔Water
✔✔A glass slide with coverslip
✔✔A dropper or pipette
✔✔A knife
Cut the potato and scrape a little amount on the glass slide. Try to
avoid large pieces of potato, the thinner the better. Drop a bit of water
over your smeared potato and cover it with the coverslip. You
can see the oval starch grains best in darkfield and/or with polarized
light. You see:
✔✔Starch grains with a cross-like appearance in polarized light or
with grain walls in darkfield
✔✔Eccentric layering of the grains, which is typical for potato starch