Oxidation possible without a Flame.--But a flame is not necessary for oxidation. Iron, if left in a damp place, becomes rusty. A union between the oxygen in the water or air and the iron makes what is known as iron oxide or rust. This is an example of _slow oxidation_. Oxidation in our Bodies.--If we expel the air from our lungs through a tube into a bottle of limewater, we notice the limewater becomes milky. Evidently carbon dioxide is formed in our own bodies and oxidation takes place there. Is it fair to believe that the heat of our body (for example, 98.6 deg. Fahrenheit under the tongue) is due to oxidation within the body, and that the work we do results from this chemical process. If so, what is oxidized? Energy comes from Foods.--From the foregoing experiment it is evident that food is oxidized within the human body to release energy for our daily work. Is it not logical to suppose that all living things, both plant and animal, release energy as the result of oxidation of foods within their cells? Let us see if this is true in the case of the pea. Food oxidized in Germinating Seeds.--If we take equal numbers of soaked peas, placed in two bottles, one tightly stoppered, the other having no stopper, both bottles being exposed to identical conditions of light, temperature, and moisture, we find that the seeds in both bottles start to germinate, but that those in the closed bottle soon stop, while those in the open jar continue to grow almost as well as similar seeds placed in an open dish would. [Illustration: Experiment that shows the necessity for air in germination.] Why did not the seeds in the covered jar germinate? To answer this question, let us carefully remove the stopper from the stoppered jar and insert a lighted candle. The candle goes out at once. The surer test of limewater shows the presence of carbon dioxide in the jar. The carbon of the foodstuffs of the pea united with the oxygen of the air, forming carbon dioxide. Growth stopped as soon as the oxygen was exhausted. The presence of carbon dioxide in the jar is an indication that a very important process which we associate with animals rather than plants, that of _respiration_, is taking place. The seed, in order to release the energy locked up in its food supply, must have oxygen, so that the oxidation of the food may take place. _Hence a constant supply of fresh air is an important factor in germination._ It is important that air should penetrate between the grains of soil around a seed. The frequent stirring of the soil enables the air to reach the seed. Air also acts upon some materials in the soil and puts them in a form that the germinating seed can use. This necessity for oxygen shows us at least one reason why the farmer plows and harrows a field and one important use of the earthworm. Explain. [Illustration: A grain of corn cut lengthwise. _C_, cotyledon; _E_, endosperm; _H_, hypocotyl; _P_, plumule.]