. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. 30 PRACTICAL COURSE IN BOTANY Let us see what became of it. Hold a lighted candle under the open end of a test tube, or under the mouth of a small glass jar. Does any vapor collect on the inside? After two or three minutes quickly invert the jar or the tube, and thrust in a lighted match: what happens? Can the substance now in the jar be ordinary air? Why not? (Exps. 21, 22.) Pour in a small quantity of limewater, holding your hand over the mouth of the tube to prevent the
. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. 30 PRACTICAL COURSE IN BOTANY Let us see what became of it. Hold a lighted candle under the open end of a test tube, or under the mouth of a small glass jar. Does any vapor collect on the inside? After two or three minutes quickly invert the jar or the tube, and thrust in a lighted match: what happens? Can the substance now in the jar be ordinary air? Why not? (Exps. 21, 22.) Pour in a small quantity of limewater, holding your hand over the mouth of the tube to prevent the air from getting in; the gas inside, being heavier than air, will not escape immediately unless agitated. What change do you notice in the limewater ? It has been proved by experiment that the kind of gas formed by the burning candle has the property of turning limewater milky; hence, whenever you see this effect produced in limewater, you may conclude that this gas, known as carbon dioxide, is present; and conversely, the presence of carbon dioxide, especially if accompanied by some of the other effects observed, as the giving out of heat and moisture, may be taken as evidence that some process similar to that going on in the burning candle is, or has been, at work. Experiment 24. Do these effects accompany any of the life processes of animals ? — Blow your breath against the palm of your hand; what sensation do you feel ? Blow it against a mirror, or a piece of common glass; what do you see ? Blow through a tube into the bottom of a glass containing limewater; how is the water affected ? How do these facts cor- respond with the results of Exp. 23 ? Experiment 25. Is there any evidence that a similar process goes on in plants ? — (1) Half fill a small, wide-mouthed jar with limewater, place it in- side a larger one (Fig. 46), and fill the space between them, up to the neck of the smaller vessel, with well- soaked peas, beans, or barleycorns, on a bed of moist cotton or bl
Size: 1142px × 2188px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorand, bookcentury1900, bookdecade1910, booksubjectbotany
