THE CHLOROPHYLL APPARATUS 



151 



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 nothing 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 2C0 2 = 2CO + 2 . At 

 the same time there is a decomposition of water, possibly 

 in the way denoted by the equation 2H 2 = 2H 2 4- 2 . 

 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 

 CH 2 0, or preferably ^ 

 HCOH. This suggested ~^4^_-_l.^gj 

 series of reactions agrees FIG. ss. APPARATUS TO SHOW THE EVOLU- 

 fairly closely with the ob- SU N N LI G H T XYGEN BY A GBEEN PLANT IN 

 served facts, but it must 



not be regarded as anything more than an hypothesis. Indeed 

 there are considerable difficulties in 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 any formation or liberation of hydrogen 

 ever been detected so . long as the plant is maintained in 

 normal conditions, 



