Question

an unpeeled potato in an osmoscope experiment may not give results. Why?

Answer 1

The skin is waterproof so water molecules won't be able to diffuse into or out of 
the potato cylinder and osmosis won't take place. This is the reason why an unpeeled potato does not give the desired results in an osmoscope experiment.

Answer 2

We need a semi permeable membrane to carry out the experiment. The peels are not semi permeable. So the experiment won't give the correct results. Instead use, cellophane paper or goat's bladder or egg's membrane