have been so defective that both froze at the same time. The latent heat
given out by a small amount of freezing water cannot counteract any great
severity of frost."

"The more water you have, then, the better?" said his father.

"Yes, for then there is more to freeze, and the effect is more gradual
and lasting."

"I feel highly honored, Webb," said his mother, smiling, "that so much
science should minister to me and my little collection of plants. I now
see that the why and wherefore comes in very usefully. But please tell me
why you put the plants that were touched with frost into cold water, and
why you will not let the sunlight fall on them?"

"For the same reason that you would put your hand in cold water if
frost-bitten. Your expression, 'touched with frost,' shows that there is
hope for them. If they were thoroughly frozen you would lose them. Your
plants, you know, are composed chiefly of water, which fills innumerable
little cells formed by the vegetable tissue. If the water in the cells is
chilled beyond a certain point, if it becomes solid ice, it expands and
breaks down the tissue of the cells, and the structure of the plant is
destroyed. If the frost can be gradually withdrawn so as to leave the
cells substantially intact, they can eventually resume their functions,
and the plant receive no very great injury."

"But why does sudden heat or sunlight destroy a frosted plant?"

"For the same reason that it breaks down the vegetable tissue. Heat
expands, and the greater the heat the more rapid the expansion. When the