"Which is which?"

"One side will make you grow taller, the other side will make you grow shorter."

"One side of what? The other side of what? thought Casey to himself.

"Of the mushroom," said the Caterpillar, just as if he had asked it aloud; and in another minute it was out of sight.

Casey remained looking thoughtfully at the mushroom for a minute, trying to make out which were the two sides of it; and as it was perfectly round, he found this a very difficult question.

[Casey had hoped to grow to the size of a Great Dane but, as is apparent, he nibbled the wrong side of the mushroom and has turned into a pygmy chihuahua instead.]