. Lessons in botany. Botany. CHAPTER XII. HOW PLANTS GET THEIR CARBON FOOD. I. The Gases Concerned. Exercise 26. 128. Gas given off by green plants in the sunlight.—Take some green alga, like spirogyra or vaucheria, which is in a fresh condition, 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 of spirogyra with black cloth so that it will be in the dark, or at least in very weak light. 129. The gas is shown in the form of bub- bles.—In a short time we that in the first vessel small b
. Lessons in botany. Botany. CHAPTER XII. HOW PLANTS GET THEIR CARBON FOOD. I. The Gases Concerned. Exercise 26. 128. Gas given off by green plants in the sunlight.—Take some green alga, like spirogyra or vaucheria, which is in a fresh condition, 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 of spirogyra with black cloth so that it will be in the dark, or at least in very weak light. 129. The gas is shown in the form of bub- bles.—In a short time we 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. Examine the vessel which was covered to exclude the light, or which was placed in the dark. Are bubbles of gas given off here? Place the vessel in the light and note how soon bubbles begin to pass Fig- 55- Oxygen gas given off by spirogyra. Exercise 27. 130. Experiment with elodea. — Take one of the higher green plants, an aquatic plant like elodea, callitriche, etc. Place the plant in the water with the cut end of the stem uppermost, but still immersed, the plant being weighed down by a glass rod or other suitable object. If we place the vessel of water 70. 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 and company
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