starch and some tincture of iodine diluted to about the color of weak
tea. Rub a few drops of the iodine on the cut surfaces of the
potatoes, parsnip, and the broken surfaces of the grains. Notice that
it turns them purple. Now drop a drop of the iodine on the laundry
starch. It turns that purple also. This experiment tells us that
plants contain starch.

=Experiment.=--Chew a piece of sorghum cane, sugar cane, cornstalk,
beet root, turnip root, apple or cabbage. They all taste sweet and
must therefore contain sugar.

Examine a number of peach and cherry trees. You will find on the trunk
and branches more or less of a sticky substance called gum.

=Experiment.=--Crush on paper seeds of cotton, castor-oil bean,
peanuts, Brazil nuts, hickory nuts, butternuts, etc. They make grease
spots; they contain fat and oil.

=Experiment.=--Chew whole grains of wheat and find a gummy
mucilaginous substance called wheat gum, or wet a pint of wheat flour
to a stiff dough, let it stand about an hour, and then wash the starch
out of it by kneading it under a stream of running water or in a pan
of water, changing the water frequently. The result will be a tough,
yellowish gray, elastic mass called gluten. This is the same as the
wheat gum and is called an albuminoid because it contains nitrogen and
is like albumen, a substance like the white of an egg.

If we crush or grate some potatoes or cabbage leaves to a pulp and
separate the juice, then heat the clear juice, a substance will
separate in a flaky form and settle to the bottom of the liquid. This