Name: ___________________________ Date: ______________ Period: ____
Cork and Onion Cells
BACKGROUND
Over 300 years ago, Robert Hooke looked at
cork under a microscope. He saw little boxlike
structures as pictured above. He called these
structures cells. Cork does not contain living
tissue and only contains a cell wall.
By the 19th century, it was accepted that all
living things are made of cells. Cells are all
different sizes and shapes but they certain
common structures.
MATERIALS
Microscope
Scalpels
Cork
Lugol’s Solution
Slides
Dropper
Onion
Paper Towels
Cover Slips
Water
Forceps
PROCEDURE
Cork Cells
1. Place a cork on a towel. Hold the cork in your hand and slice very
thin sections of cork using a scalpel. Be sure you slice away from
your fingers.
2. Place a drop of water on a microscope slide. Place your thin piece
of cork on the water and then cover the cork with a coverslip as
shown below.
3. Place your slide on the stage of your microscope and view it
under the low power (10X) objective lens. Focus ONLY with the
coarse adjustment knob. Draw a picture of what you see and
label the parts. HINT: Remember that cork is not alive
4. Change the microscope to high power (40X) magnification and
focus using ONLY the fine adjustment knob. Draw a picture of
your cork cells in the field of view below. Label your drawing.
PROCEDURE
Onion Skin
1. You will be given a part of a bulb of onion. Separate the layers.
In between these layers, there is a very thin skin. Cut a very
small square (about .5 cm) through the paper thin epidermis.
2. Use your forceps to lift the very thin piece of epidermis off of the
onion layer. Place it on your slide with a drop of water and add a
cover slip as shown in step 2 above using cork.
3. View your onion skin under low power (100X). Draw and label
your diagram.
4. View your onion skin under high power (400X). Draw and label
your diagram.
5. Notice the parts that you were able to see in your previous
diagram. Cell parts are transparent (you can see through them)
so you must use a stain in order to see some of the organelles.
6. Place Lugol’s solution (Iodine) on your slide as shown below.
7. Look at your onion skin under low and high power and draw each
below. Label the parts that you see.
Low Power
High Power
Conclusion
Answer the following questions based on your observations in your
lab.
1. How can you tell that cork cells are nonliving?
2. What did Hooke actually see when he looked at cork cells?
3. What structures did you see in the onion skin cells that you did
not see in cork cells?
4. What structures did you see in both onion skin and cork cells?
5. What are the benefits of using stain on the onion skin cells?
6. What is the disadvantage of using stain on the onion skin cells?