Every one has seen a cornfield. If you pluck up one of the innumerable
=wheat plants= which are fixed in the soil of the field, about harvest
time, you will find that it consists of a stem which ends in a =root= at
one end and an =ear= at the other, and that blades or =leaves= are
attached to the sides of the stem. The ear contains a multitude of oval
grains which are the =seeds= of the wheat plant. You know that when
these seeds are cleared from the =husk= or =bran= in which they are
enveloped, they are ground into fine powder in mills, and that this
powder is the =flour= of which bread is made. If a handful of flour
mixed with a little cold water is tied up in a coarse cloth bag, and the
bag is then put in a large vessel of water and well kneaded with the
hands, it will become pasty, while the water will become white. If this
water is poured away into another vessel, and the kneading process
continued with some fresh water, the same thing will happen. But if the
operation is repeated the paste will become more and more sticky, while
the water will be rendered less and less white, and at last will remain
colourless. The sticky substance which is thus obtained by itself is
called =gluten=; in commerce it is the substance known as =maccaroni=.
If the water in which the flour has thus been washed is allowed to stand
for a few hours, a white sediment will be found at the bottom of the
vessel, while the fluid above will be clear and may be poured off. This
white sediment consists of minute grains of =starch=, each of which,
examined with the microscope, will be found to have a concentrically
laminated structure. If the fluid from which the starch was deposited is
now boiled it will become turbid, just as white of egg diluted with
water does when it is boiled, and eventually a whitish lumpy substance
will collect at the bottom of the vessel. This substance is called
=vegetable albumin=.
Besides the albumin, the gluten, and the starch, other substances, about
which this rough method of analysis gives us no information, are
contained in the wheat grain. For example, there is woody matter or
=cellulose=, and a certain quantity of =sugar= and =fat=. It would be
possible to obtain a substance similar to albumin, starch, saccharine
and fatty matters, and cellulose, by treating the stem, leaves, and root
in a similar fashion, but the cellulose would be in far larger
proportion. =Straw=, in fact, which consists of the dry stem and leaves
of the wheat plant, is almost wholly made up of cellulose. Besides this,
however, it contains a certain proportion of mineral bodies, among them,
pure flint or =silica=; and, if you should ever see a wheat rick burnt,
you will find more or less of this silica, in a glassy condition, in the
embers. In the living plant, all these bodies are combined with a large
proportion of water, or are dissolved, or suspended in that fluid. The
relative quantity of water is much greater in the stem and leaves than
in the seed.