, we find it
abundantly supplied with water, but _no air_. Here again,
therefore, germination cannot take place. It may be well to state
here that this can never occur _exactly_ in nature, because, water
having the power of dissolving air to a certain extent, the seed
_a_ in Fig. 2 is, in fact, supplied with a _certain_ amount of
this necessary substance; and, owing to this, germination does
take place, although by no means under such advantageous
circumstances as it would were the soil in a better condition.

[Illustration: Fig. 3 - A DRAINED SOIL.]

Fig. 3 - A DRAINED SOIL.

"We pass on now to Fig. 3. Here we find a different state of
matters. The canals are open and freely supplied with air, while
the pores are filled with water; and, consequently, you perceive
that, while the seed _a_ has quite enough of air from the canals,
it can never be without moisture, as every particle of soil which
touches it is well supplied with this necessary ingredient. This,
then, is the proper condition of soil for germination, and in fact
for every period of the plant's development; and this condition
occurs when the soil is _moist_, but not _wet_,--that is to say,
when it has the color and appearance of being well watered, but
when it is still capable of being crumbled to pieces by the hands,
without any of its particles adhering together in the familiar
form of mud."

As plants grow under the same conditions, as to soil, that are necessary
for the germination of seeds, the foregoing explanation of the relation of
water to the particles of the soil is perfectly applicable to the whole
period of vegetable growth. The soil, to the entire depth occupied by
roots, which, with most cultivated plants is, in drained land, from two to
four feet, or even more, should be maintained, as nearly as possible, in
the condition represented in Fig. 3,--that is, the particles of soil should
hold water by attraction, (absorption,) and the spaces between the
particles should be filled with air. Soils which require drainage are not
in this condition. When they are not saturated with water, they are
generally dried into lumps and clods, which are almost as impenetrable by
roots as so many stones. The moisture which these clods contain is not
available to plants, and their surfaces are liable to be dried by the too
free