or force of osmose.

[Illustration: FIG. 10.
A plow stopped in the furrow, to show what it does to the roots of
plants when used for after-cultivation. Notice the point of the plow
under the roots.]

[Illustration: FIG. 11.
A corn-plant ten days after planting the seed. To show how quickly the
roots reach out into the soil. Some of the roots were over 18 inches
long.]

=Experiment.=--Procure a wide-mouthed bottle, an egg, a glass tube
about three inches long and a quarter-inch in diameter, a candle, and
a piece of wire a little longer than the tube. Remove a part of the
shell from the large end of the egg without breaking the skin beneath.
This is easily done by gently tapping the shell with the handle of a
pocket-knife until it is full of small cracks, and then, with the
blade of the knife, picking off the small pieces. In this way remove
the shell from the space about the size of a nickel. Remove the shell
from the small end of the egg over a space about as large as the end
of the glass tube. Next, from the lower end of the candle cut a piece
about one-half inch long. Bore a hole in this just the size of the
glass tube. Now soften one end of the piece of candle with the hole
in it and stick it on to the small end of the egg so that the hole in
the candle comes over the hole in the egg. Heat the wire, and with it
solder the piece of candle more firmly to the egg, making a
water-tight joint. Place the glass tube in the hole in the piece of
candle, pushing it down till it touches the egg. Then, with the heated
wire, solder the tube firmly in place. Now run the wire down the tube