THE CHLOBOPHYLL APPAKATUS 159 



brought about by the chloroplast as certainly as is the 

 original change of the carbon dioxide. 



We have so far assumed that a sugar having the formula 

 C 6 H 12 6 , and known as a hexose, is the first carbohydrate 

 formed. This, however, is not certain. Some experi- 

 ments carried out in 1892 by Brown and Morris point 

 rather to cane-sugar as the first carbohydrate synthesised. 

 Cane-sugar is a more complex substance, and has the 

 formula C 12 H 23 O n . This conclusion was based on repeated 

 observations that when leaves of Tropceolum were plucked 

 and then exposed to sunlight for twelve hours, there was a 

 great accumulation of this sugar in the leaf, while the 

 simpler hexoses did not increase in quantity. The severance 

 of the leaves from their stems prevented the transport of 

 the sugars to any other part of the plant, so that they accumu- 

 lated at the seat of their formation. 



Further investigations on this point are, however, necessary 

 before a definite conclusion can be arrived at. It is not 

 impossible that the cane-sugar of Tropaeolum may be a 

 form of stored material temporarily deposited as starch is. 

 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 

 C0 2 + 2H = HCOOH + H 3 2 , and that then they are 

 decomposed, yielding formaldehyde and water, and giving 

 off oxygen, HCOOH + H 2 2 = HCOH + H 2 -f 2 . 



A theory of a totally different nature was advanced some 

 years ago by Vines. Starting with the observation that 

 a carbohydrate substance (cellulose) is produced or secreted 

 by protoplasm in the process of the thickening of cell-walls, 

 and noticing the formation of starch grains in the chloroplast 

 almost as soon as the photosynthesis has been established, 

 he argued that the carbohydrate is not directly formed 



