214 STRUCTURAL BOTANY 



hydrogen. Both of these are bodies which readily 

 form new combinations. Now, as we learnt some time 

 back (see p. 36), we find in most plants, though not in 

 all, that starch granules soon make their appearance 

 in the chlorophyll corpuscles when carbon-assimila- 

 tion is going on. In some of the simpler plants an ex- 

 posure to sunlight for only five minutes is sufficient to 

 cause the formation of starch in the chlorophyll bodies, 

 when none had been present before. In darkness, or 

 in the absence of carbon dioxide, the starch disappears, 

 and is not replaced. The chemical elements of starch 

 are present in the proportions C G H 10 5 ; we must not 

 suppose, however, that starch is ever the direct product 

 of assimilation. In all cases a sugar of some kind 

 makes its appearance before starch. Sometimes the 

 sugar formed appears to be grape-sugar or glucose, 

 which has the formula C 6 H 12 6 ; while in other cases 

 cane-sugar (C 12 H 22 O n ) is said to be the first demon- 

 strable product of assimilation. How the sugar is 

 formed we cannot say, though it is easy to give a 

 chemical equation for the process ; thus, supposing 

 grape-sugar to be formed, the equation would be 



6(00) + 6(H 2 ) = C 6 H J2 6 ; 



it is quite certain, however, that nothing so simple as 

 this takes place in nature. There is a body called 

 Formic Aldehyde (CH 2 0) which has been supposed 

 to represent an intermediate stage in the process 



) = C 6 H 12 6 . 



Many kinds of sugar have recently been made from 

 inorganic compounds in the laboratory, and this is 



