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You have perhaps observed the regularity of arrangement in the twigs and

branches of trees. Now pull up the roots of a plant, as, for example,

sheep sorrel, Jimson weed, or some other plant. Note the branching of

the roots. In these there is no such regularity as is seen in the twig.

Trace the rootlets to their finest tips. How small, slender, and

delicate they are! Still we do not see the finest of them, for in taking

the plant from the ground we tore the most delicate away. In order to

see the real construction of a root we must grow one so that we may

examine it uninjured. To do this, sprout some oats in a germinator or in

any box in which one glass side has been arranged and allow the oats to

grow till they are two or more inches high. Now examine the roots and

you will see very fine hairs, similar to those shown in the accompanying

figure, forming a fuzz over the surface of the roots near the tips. This

fuzz is made of small hairs standing so close together that there are

often as many as 38,200 on a single square inch. Fig. 17 shows how a

root looks when it has been cut crosswise into what is known as a cross

section. The figure is much increased in size. You can see how the

root-hairs extend from the root in every direction. Fig. 18 shows a

single root-hair very greatly enlarged, with particles of sand sticking

to it.

Highly magnified]

These hairs are the feeding-organs of the roots, and they are formed

only near the tips of the finest roots. You see that the large, coarse

roots that you are familiar with have nothing to do with _absorbing_

plant food from the soil. They serve merely to _conduct_ the sap and

nourishment from the root-hairs to the tree.

When you apply manure or other fertilizer to a tree, remember that it is

far better to supply the fertilizer to the roots that are at some

distance from the trunk, for such roots are the real feeders. The plant

food in the manure soaks into the soil and immediately reaches the

root-hairs. You can understand this better by studying the distribution

of the roots of an orchard tree, shown in Fig. 19. There you can see

that the fine tips are found at a long distance from the main trunk.


You can now readily see why it is that plants usually wilt when they are

transplanted. The fine, delicate root-hairs are then broken off, and the

plant can but poorly keep up its food and water supply until new hairs

have been formed. While these are forming, water has been evaporating

from the leaves, and consequently the plant does not get enough moisture

and therefore droops.

Would you not conclude that it is very poor farming to till deeply any

crop after the roots have extended between the rows far enough to be cut

by the plow or cultivator? In cultivating between corn rows, for

example, if you find that you are disturbing fine roots, you may be sure

that you are breaking off millions of root-hairs from each plant and

hence are doing harm rather than good. Fig. 20 shows how the roots from

one corn row intertangle with those of another. You see at a glance how

many of these roots would be destroyed by deep cultivation. Stirring

the upper inch of soil when the plants are well grown is sufficient

tillage and does no injury to the roots.

A deep soil is much better than a shallow soil, as its depth makes it

just so much easier for the roots to seek deep food. Fig. 21 illustrates

well how far down into the soil the alfalfa roots go.


Dig up the roots of several cultivated plants and weeds and compare

them. Do you find some that are fine or fibrous? some fleshy like

the carrot? The dandelion is a good example of a tap-root.

Tap-roots are deep feeders. Examine very carefully the roots of a

medium-sized corn plant. Sift the dirt away gently so as to loosen

as few roots as possible. How do the roots compare in area with the

part above the ground? Try to trace a single root of the corn plant

from the stalk to its very tip. How long are the roots of mature

plants? Are they deep or shallow feeders? Germinate some oats or

beans in a glass-sided box, as suggested, and observe the