hairs; and also remember the experiment which showed us that roots
need air, we can readily see that free water would give the root hairs
enough moisture, but it would at the same time drown them by cutting
off the air. Therefore free water is not directly useful to the roots
of house plants or farm plants, excepting such as are naturally
swamp plants, like rice, which grows part of the time with its
roots covered with free water.

[Illustration: FIG. 26.--CAPILLARY TUBES.
To show how water rises in small tubes or is drawn into small spaces.]

[Illustration: FIG. 27.--CAPILLARY PLATES.
Water is drawn to the highest point where the glass plates are closest
together.]

[Illustration: FIG. 28.
A cone of soil to show capillarity. Water poured about the base of
this cone of soil has been drawn by capillary force half-way to the
top.]

[Illustration: FIG. 29.
To show the relative amounts of film-moisture held by coarse and fine
soils. The colored water in bottle _A_ represents the amount of water
required to cover the half pound of pebbles in the tumbler _B_ with a
film of moisture. The colored water in bottle _C_ shows the amount
required to cover the soil grains in the half pound of sand in tumbler
_D._]


CAPILLARY WATER