. A civic biology : presented in problems. Biology; Sanitation. PLANTS MAKE FOOD 95 the food is stored in such a stable form that it may be sent to all parts of the world in the form of grain or other fruits. Animals, herbivorous and flesh-eating, man himself, all are dependent upon the starch-making processes of the green plant for the ultimate source of their food. When we remember that in 1913 in the United States the total value of all farm crops was over $6,000,000,000, and when we realize that these products came from the air and soil through the energy of the sun, we may begin to realiz
. A civic biology : presented in problems. Biology; Sanitation. PLANTS MAKE FOOD 95 the food is stored in such a stable form that it may be sent to all parts of the world in the form of grain or other fruits. Animals, herbivorous and flesh-eating, man himself, all are dependent upon the starch-making processes of the green plant for the ultimate source of their food. When we remember that in 1913 in the United States the total value of all farm crops was over $6,000,000,000, and when we realize that these products came from the air and soil through the energy of the sun, we may begin to realize why as city boys and girls the study of plant biology is of importance to us. Green Plants give off Oxygen in Sun- light. - - In still another way green plants are of direct use to us in the city. Dur- ing this process of starch-making oxygen is given off as a by-product. This may easily be proven by the following experi- Place any green water plant in a battery jar partly filled with water, cover the plants with a glass funnel and mount a test tube full of water over the mouth of the funnel. Then place the apparatus in a warm sunny window. Bubbles of gas are seen to rise from the plant. After two or three hours of hot sun, enough of the gas can be obtained by displacement of the water to make the oxygen test. That oxygen is given off as a by-product by green plants is a fact of far-reaching Experiment importance. City parks are true " breath- ing ; The green covering of the earth is giving to animals an element that they must have, while the animals in their turn are supplying to the plants carbon dioxide, a compound used in food-making. Thus a widespread relation of mutual helpfulness exists between plants and animals. 1 Immediate success with this experiment will be obtained if the water has been previously charged with carbon to show that oxygen is given off by green plants in the sun- Please note that these images are extracted f
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