al roots will be found within two or three inches of the surface,
and little rootlets from these will be found reaching up as near the
surface as there is a supply of moisture. After a continued period of
wet weather, if the soil has not been disturbed, roots will be found
coming to the very surface and even running along the top of the soil.

As to the fourth question, How far do roots reach out sidewise or
laterally from the plant? you will find roots extending three, four,
five and even six or more feet from the plant. They have numerous
branches and rootlets, which fill all parts of the upper soil. Tree
roots have been found thirty or forty feet in length.

We started on this observation lesson to find out something about the
habit of growth of roots, so that we could tell how the roots do their
work for the plant. But before going on with that question, let us
stop right here and see whether we cannot find some very important
lessons for the farmer and plant grower from what we have already
seen. Is a knowledge of these facts we have learned about roots of any
value to the farmer? Let us examine each case and see.

Of what value is it to the farmer to know that the larger part of the
roots of farm plants develop in that part of the soil that has been
plowed or spaded? It tells him that plowing tends to bring about the
soil conditions which are favorable to the growth and development of
roots. Therefore, the deeper he plows, the deeper is the body of the
soil having conditions best suited for root growth, and the larger
will be the crop which grows above the soil.

Of what value is it to the farmer to know that the roots of farm
plants penetrate to depths of five or six feet in the soil? To answer
this question it will be necessary for us to know something of the
conditions necessary for root growth. So we will leave this till
later.

Of what value is it to the farmer to know that many of the roots of
his farm plants come very near the surface of the soil? It tells him
that he should be careful in cultivating his crop to injure as few of
these roots as possible. In some parts of the country, particularly in
the South, the tool commonly used for field cultivation is a small
plow. This is run alongside of the row, throwing the soil from the
crop, and then again throwing the soil to the crop. Suppose we
investigate, and see how this affects the roots of the crop.

[Illustration: FIG. 8.
Sweet potato roots. The g