thers are harmful.

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CHAPTER VIII

THE SOIL AND THE PLANT

Apparatus required.

_Dry powdered soil, sand, clay, leaf mould, seeds. Six funnels, disks,
stands and glass jars [3]. Six glass tubes about 1/2 in. diameter and
18 in. long [2]. Muslin, string, three beakers. Six lamp chimneys
standing in tin lids [3]. Pot experiments (p. xiii), growing plant.
Two test tubes fitted with split corks (Fig. 35)._

If you have ever tried to grow a plant in a pot you must have
discovered that it needs much attention if it is to be kept alive. It
wants water or it withers; it must be kept warm enough or it is killed
by cold; it has to be fed or it gets yellow and starved; also it needs
fresh air and light. These five things are necessary for the plant:

Water,
Warmth,
Food,
Fresh air,
Light.

We may add a sixth: there must be no harmful substance present in the
soil.

Wild plants growing in their native haunts get no attention and yet
their wants are supplied. We will try and find out how this is done.

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[Illustration: Fig. 29. Loam and sand both retain water, but loam
better than sand]

Water comes from the rain, but the rain does not fall every day. How
do the plants manage to get water on dry days? A simple experiment
will show you one way. Put about four tablespoonsful of dry soil on to
the funnel shown in Fig. 29 and then pour on two tablespoonsful of
water. Measure what runs through. You will find it very little; most
of the water sticks to the soil. Even after several days the soil was
still rather moist. Soil has the power of keeping a certain amount of
water in reserve for the plant, it only allows a small part of the rain
to run through. Do the experiment also with sand, powdered clay, and
leaf mould. Some water always remains behind, but less in the case of
sand than in the others. In one {66} experiment 30 cubic centimetres
of water were poured on to 50 grains of soil but only 10 cubic
centimetres passed through, but when an equal amount was poured on to
50 grains of sand no less than 20 cubic centimetres passed through.
Very sandy soils, therefore, possess less power of storing water than
do soils with more clay or mould in them, such as loams, clays or black
soils.

[Illustration: Fig. 30. Water can rise upwards in soil. It can, in
fact, travel in any direction, from wet to dry places]

Further, water has a wonderful power of passing f