. An introduction to vegetable physiology. Plant physiology. 156 VEGETABLE PHYSIOLOGY The apparatus shown in fig. 88 will enable this inter- change of gases to be seen. Into a glass jar is poured some water containing carbon dioxide in solution. Some aquatic plant is put into the water and a funnel inserted above it, the end of which rises into a burette filled with water and closed by a stopcock. The whole apparatus being placed in sunlight, bubbles of oxygen will be given off by the leaves and will rise into the burette. If no carbon dioxide is in the water, no oxygen will be given off. Ther
. An introduction to vegetable physiology. Plant physiology. 156 VEGETABLE PHYSIOLOGY The apparatus shown in fig. 88 will enable this inter- change of gases to be seen. Into a glass jar is poured some water containing carbon dioxide in solution. Some aquatic plant is put into the water and a funnel inserted above it, the end of which rises into a burette filled with water and closed by a stopcock. The whole apparatus being placed in sunlight, bubbles of oxygen will be given off by the leaves and will rise into the burette. If no carbon dioxide is in the water, no oxygen will be given off. There is little certainly known at present as to the details of the changes which connect these two phenomena. It has been suggested by Baeyer that the carbon dioxide is decomposed with the formation of carbon monoxide and oxygen, according to the equation 2CO3 = 2C0 + 0^. At the same time there is a decomposition of water, possibly in the way denoted by the equation 2H2O = 2Ho + On- The oxygen is given off, the volume being found, when care- fully measured, to be equal to the volume of carbon dioxide undergoing de- composition. The carbon monoxide and the hydro- gen are then thought to unite, producing form- aldehyde, a body repre- sented by the formula CH3O, or preferably HCOH. This suggested series of reactions agrees fairly closely with the ob- served facts, but it must not be regarded as anything more than an hypothesis. Indeed there are considerable difficulties m accepting it as it stands. There is no evidence that carbon monoxide is formed. Experiments have shown that this gas is quite useless to most plants ; if it is supplied in the place of the dioxide, the formation of carbohydrates does not take place. Nor has. Fig. 88.—Appaeatus to show the Evolu- tion 01? Oxygen by a Geeen Plant IN 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 m
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