THE CHLOROPHYLL APPARATUS 167 



of the quantity needed by the cell for immediate consump- 

 tion. 



If we accept the view of the polymerisation of formalde- 

 hyde to give rise to the sugar, we cannot withdraw this 

 operation also from the activity of the chloroplast. Sugars 

 are what are called optically active compounds ; that is, they 

 possess the power of deflecting a ray of polarised light to 

 the right or to the left as the latter is made to pass through 

 either crystals or a solution of them. Formaldehyde has no 

 such power. There is no process known by which an 

 optically active compound is formed from an optically 

 inactive one without the intervention of living substance. 

 Consequently we must suppose that the polymerisation is 

 brought about by the chloroplast as certainly as is the 

 original decomposition of the carbon dioxide. 



We have so far assumed that a sugar having the 

 formula C G H 12 (i , and known as a hexose, is the first carbo- 

 hydrate formed. This, however, is not certain. Some ex- 

 periments 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 22 U . This conclusion is based on repeated observations 

 that when leaves of Trop&olum were plucked and then ex- 

 posed to sunlight for twelve hours, there was a great accu- 

 mulation 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 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 



