. Botany all the year round; a practical text-book for schools. Botany. 22 THE LEAF from the gases mixed with the water, and giving off. It is even more active in separating oxygen from the air, but the process is not visible to the eye, because we cannot see a gas except in the form of bubbles. Water is used not as an aid to the plant in the performance of its function, but in order to enable us to see the result. 23. Leaves as Purifiers of the Atmosphere. â Fill two tumblers with water, to expel the air, and invert in a shallow dish of water, having first introduced a freshly cut sprig of so
. Botany all the year round; a practical text-book for schools. Botany. 22 THE LEAF from the gases mixed with the water, and giving off. It is even more active in separating oxygen from the air, but the process is not visible to the eye, because we cannot see a gas except in the form of bubbles. Water is used not as an aid to the plant in the performance of its function, but in order to enable us to see the result. 23. Leaves as Purifiers of the Atmosphere. â Fill two tumblers with water, to expel the air, and invert in a shallow dish of water, having first introduced a freshly cut sprig of some healthy green plant into one of them. Then by means of a bent tube blow into the mouth of each tumbler till all the water is expelled by the impure air from the lungs. Set the dish in the sunshine and leave ' for showing it, taking care that the end of the iiow leaves purify the atmos- cutting is in the water of the dish. phere. ^ r r â i i After forty-eight hours remove the tumblers by running under the mouth of each, before lift- ing from the dish, a piece of glass well coated with vase- line (lard will answer) and pressing it down tight so that no air can enter. Place the tumblers in an upright position, keeping them securely covered. Fasten a lighted taper or match to the end of a wire, plunge it quickly first into one tumbler, then into the other, and note the result. It is an established fact that a light will not burn in an impure atmosphere; this is why well cleaners spnd down a lighted candle before going into a well themselves. What are we to infer from the effects observed ^s to the action of the plant upon the atmosphere ? This experiment will not succeed unless performed very carefully, and the air must be absolutely excluded from the tumblers until the instant the taper is plunged in. 24. Leaves as Food Makers. â It thus appears that plants are constantly reversing the effects of animal res- piration by giving off oxygen and absorbing carbon dio
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