THE CHLOROPHYLL APPARATUS 161 
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 2CO, = 2C0 + 0,. At 
the same time there is a decomposition of water, possibly 
in the way denoted by the equation 2H,O = 2H, + O,,. 
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,O, or preferably 
HCOH. This suggested 
series of reactions agrees Fre. 88.—Aprararus To snow THE EvoLv- 
fairly closely with the ob- aoa BY A GREEN PLANT IN 
served facts, but it must 
notbe 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, 
