- a plant with big leaves - a jar of petroleum jelly - Take a
blob of jelly and coat the top side of a leaf. Make sure to
apply a thick layer all over. - Take another blob and cover the
bottom side of a different leaf. - In a few days, one leaf will
look just fine. - But the other leaf will curl up and wither.
That's because it can't breathe. Which leaf curled up after a
few days?