The chemists tell us that these substances are composed of certain
chemical elements, some of which the plant obtains from the air, some
from the soil and some from water.

The following table gives the substances found in plants, the elements
of which they are composed, and the sources from which the plants
obtain them:

----------------------------------------------------------+
Substances found | Elements of which | Sources from |
in plants. | they are made. | which plants |
| | obtain them. |
-------------------+---------------------+----------------+
Cellulose or | | |
woody fibre | Carbon | Air |
Starch |---------------------+----------------+
Sugar | | |
Gum | Oxygen | Water |
Fat and Oil | Hydrogen | |
-------------------+---------------------+----------------+
| Carbon | Air |
+---------------------+----------------+
Albuminoids | Oxygen | Water |
| Hydrogen | |
+---------------------+----------------+
| _Nitrogen_ | |
| Sulphur | |
| Phosphorus | |
-------------------+---------------------| Soil +
| _Phosphorus_ | |