154 VEGETABLE PHYSIOLOGY 
any other part of the plant, so that they accumulated at the 
seat of their formation. 
Further investigations on this point are, however, 
necessary before a definite conclusion can be arrived at. 
This theory of the processes of photosynthesis is by no 
means the only one which has been advanced, though on 
the whole it is that which has been received with most 
favour. A modification of Baeyer’s view was advanced by 
Erlenmeyer, who suggested that the first interaction of 
carbon dioxide and water leads to the formation of formic 
acid and hydrogen peroxide, according to the equation 
CO, + 2H,O = HCOOH + H,0,, and that then they are 
decomposed, yielding formaldehyde and water, and giving 
off oxygen, HCOOH + H,O, = HCOH + H,0 + 0,. 
An hypothesis of a different nature was put forward 
by Crato many years later. He suggested that the carbon 
dioxide after absorption becomes orthocarbonic acid, 
C(OH),, which exists in solution in the cell-sap. The 
orthocarbonic acid has the structure of a closed benzene 
ring in which six molecules are linked together. This 
becomes decomposed, liberating six molecules of water 
and six molecules of oxygen, and forming a hexavalent 
phenol :—6C(OH), = C,H,(OH), + 60, + 6H,0. This new 
body then undergoes a molecular rearrangement and 
becomes glucose, C,H,(OH), = C,H,,0,. 
This view is purely hypothetical, and cannot claim to 
be based on experiment. 
A more recent suggestion on this subject is that made 
by Bach in 1893. He points out that when sulphurous 
acid, H,80O,, is exposed to light, it becomes transformed to 
sulphuric acid, sulphur and water being split off, 3H,80, = 
2H,80, + H,O + 8, and he argues that a similar process 
analogous with this reaction takes place in a leaf. The 
carbon dioxide unites with water and forms carbonic acid, 
which is then split up in the same way as the sulphurous 
acid, 8H,CO, = 2H,CO, + H,O + ©. The carbon and 
water are not set free separately, but in combination as 
