. Elementary botany. Botany. CHAPTER VIII. DIFFUSION OF GASES. 111. Gas given off by green plants in the sunlight.—Let us take some green alga, like spirogyra, which is in a fresh con- dition, and place one lot in a beaker or tall glass vessel of water and set this in the direct sunlight or in a well lighted place. At the same time cover a similar vessel with spirogyra with black cloth so that it will be in the dark, or at least in very weak light. 112. In a short time we note that in the first vessel small bubbles of gas are accumulating on the surface of the threads of the spirogyra, and now
. Elementary botany. Botany. CHAPTER VIII. DIFFUSION OF GASES. 111. Gas given off by green plants in the sunlight.—Let us take some green alga, like spirogyra, which is in a fresh con- dition, and place one lot in a beaker or tall glass vessel of water and set this in the direct sunlight or in a well lighted place. At the same time cover a similar vessel with spirogyra with black cloth so that it will be in the dark, or at least in very weak light. 112. In a short time we note that in the first vessel small bubbles of gas are accumulating on the surface of the threads of the spirogyra, and now and then some free themselves and rise to the surface of the water. Where there is quite a tangle of the threads the gas is apt to become caught and held back in larger bubbles, which on agitation of the vessel are freed. If We now examine the Second vessel Oxygen gas given off by spirogyra. we see that there are no bubbles, or only a very few of them. We are led to believe then that sunlight has had something to do with the setting free of this gas from the plant. 113. We may now take another alga like vaucheria and per- form the experiment in the same way, or to save time the two may be set up at once. In fact if we take any of the green 49. Fig- 44-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Atkinson, George Francis, 1854-1918. New York, H. Holt
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