rays of the sun, which contain a great deal of heat, fall on any part of
a frost-bitten plant, that part begins to expand so rapidly and violently
that the cellular tissues are ruptured, and life is destroyed. What is
more, the heat does not permeate equally and at once the parts affected
by frost. The part furthest away from the heat remains contracted, while
the parts receiving it expand rapidly and unequally, and this becomes
another cause for the breaking up of the vegetable tissue. The same
principle is illustrated when we turn up the flame of a lamp suddenly.
The glass next to the flame expands so rapidly that the other parts
cannot keep pace, and so, as the result of unequal expansion, the chimney
goes to pieces. With this principle in mind, we seek to withdraw the
frost and to reapply the vivifying heat very gradually and equally to
every part, so that the vegetable tissues may be preserved unbroken. This
is best done by immersing them in cold water, and then keeping them at a
low temperature in a shady place. As the various parts of the plant
resume their functions, the light and heat essential to its life and
growth can gradually be increased."

"It seems to me that your theory is at fault, Webb," said Leonard. "How
is it that some plants are able to endure such violent alternations of
heat and cold?"

"We don't have to go far--at least I do not--before coming to the
limitations of knowledge. What it is in the structure of a plant like the
pansy, for instance, which makes it so much more hardy than others that
seem stronger and more vigorous, even the microscope does not reveal.
Nature has plenty of secrets that she has not yet told. But of all people
in the world those who obtain their livelihood from the soil should seek
to learn the wherefore of everything, for such knowledge often doubles
the prospect of success."