nd
leaves above. The water, carrying plant food with it, rises in a simple
but peculiar way through the roots and stems.

The plants use the food for building new tissue, that is, for growth.
The water passes out through the leaves into the air. When the summers
are dry and hot and there is but little water in the soil, the leaves
shrink up. This is simply a method they have of keeping the water from
passing too rapidly off into the air. I am sure you have seen the corn
blades all shriveled on very hot days. This shrinkage is nature's way of
diminishing the current of water that is steadily passing through the
plant.

A thrifty farmer will try to keep his soil in such good condition that
it will have a supply of water in it for growing crops when dry and hot
weather comes. He can do this by deep plowing, by subsoiling, by adding
any kind of decaying vegetable matter to the soil, and by growing crops
that can be tilled frequently.

The soil is a great storehouse for moisture. After the clouds have
emptied their waters into this storehouse, the water of the soil comes
to the surface, where it is evaporated into the air. The water comes to
the surface in just the same way that oil rises in a lamp-wick. This
rising of the water is called _capillarity_.

[Illustration: FIG. 5. AN ENLARGED VIEW OF A SECTION OF MOIST SOIL,
SHOWING AIR SPACES AND SOIL PARTICLES]

It is necessary to understand what is meant by this big word. If into a
pan of water you dip a glass tube, the water inside the tube rises above
the level of the water in the pan. The smaller the tube the higher will
the water rise. The greater rise inside is perhaps due to the fact that
the glass attracts the particles of water more than the particles of
water attract one another. Now apply this principle to the soil.

[Illustration: FIG. 6. THE RIGHT WAY TO PLOW]

The soil particles have small spaces between them, and the spaces act
just as the tube does. When the water at the surface is carried away by
drying winds and warmth, the water deeper in the soil rises through
the soil spaces. In this way water is brought from its soil storehouse
as plants need it.

[Illustration: FIG. 7. APPARATUS FOR TESTING THE HOLDING OF WATER BY
DIFFERENT SOILS]

Of course when the underground water reaches the surface it evaporates.
If we want to keep it for our crops, we must prepare a trap to hold it.
Nature has shown us how this can be done. Pick up a plank as it lies on