is vegetable albumen.

[Illustration: FIG. 34.
Soy-bean roots. Showing nodules of tubercles, the homes of
nitrogen-fixing bacteria.]

[Illustration: FIG. 35.
Garden-pea roots, showing tubercles or nodules, the homes of
nitrogen-fixing bacteria.]

=Experiment.=--Crush the leaves or stems of several growing plants and
notice that the crushed and exposed parts are moist. In a potato or an
apple we find a great deal of moisture. Plants then are partly made of
water. In fact growing plants are from 65 to 95 per cent. water.

=Experiment.=--Expose a plant or part of a plant to heat; the water is
driven off and there remains a dry portion. Heat the dry part to a
high degree and it burns; part passes into the air as smoke and part
remains behind as ashes.

We have found then the following substances in plants: Woody fibre or
cellulose, starch, sugar, gum, fats and oils, albuminoids, water,
ashes. Aside from these are found certain coloring matters, certain
acids and other matters which give taste, flavor, and poisonous
qualities to fruits and vegetables. More or less of all these
substances are found in all plants. Now these are all compound
substances. That is, they can all be broken down into simpler
substances, and with the exception of the water and the ashes, the
plants do not take them directly from the soil.