:--

ALKALIES. ACIDS. NEUTRALS.

Potash. Sulphuric acid. Silica.
Soda. Phosphoric " Chlorine.
Lime. Oxide of Iron.
Magnesia. " Manganese.

FOOTNOTES:

[B] Bromine, iodine, etc., are sometimes detected in particular plants,
but need not occupy the attention of the farmer.

[C] This classification is not strictly scientific, but it is one which
the learner will find it well to adopt. These bodies are called neutrals
because they have no decided alkaline or acid character.

[D] In some soils the _fluorides_ undoubtedly supply plants with soluble
silicates, as _fluoric acid_ has the power of dissolving silica. Thus,
in Derbyshire (England), where the soil is supplied with fluoric acid,
grain is said never to lodge.

[E] Sourness.

[F] There is reason to suppose that _alumina_ is an essential
constituent of many plants.

CHAPTER V.

GROWTH.

[Of what does a perfect young plant consist?

How must the food of plants be supplied?

Can carbon and earthy matter be taken up at separate stages of growth,
or must they both be supplied at once?]

Having examined the materials of which plants are made, it becomes
necessary to discover how they are put together in the process of
growth. Let us therefore suppose a young wheat-plant for instance to be
in condition to commence independent growth.

It consists of roots which are located in the soil; leaves which are
spread in the air, and a stem which connects the roots and leaves. This
stem contains sap vessels (or tubes) which extend from the ends of the
roots to the surfaces of the leaves, thus affording a passage for the
sap, and consequently allowing the matters taken up to be distributed
throughout the plant.

[What seems to be nature's law with regard to this?

What is the similarity between making a cart and raising a crop?

In the growth of a young plant, what operations take place about the
same time?]

It is necessary that the materials of which plants are made should be
supplied in certain proportions, and at the same time. For instance,
carbon could not be taken up in large quantities by the leaves, unless
the roots, at the same time, were receiving from the soil those mineral
matters which are necessary to growth. On the other hand, no
considerable amount of earthy matter could be appropriated by the roots
unless the leaves were obtaining carbon from the air. This same r