THE CARBOHYDRATES OF THE ANGIOSPERM LEAF 35 



glucose, and there is a certain amount of evidence in favour 

 of the view that this process is reversible, and that sucrose 

 may be formed in the plant from glucose, with the isomeric 

 rearrangement of glucose to give eZ-fructose as an inter- 

 mediate step. It has, however, been shown by Hudson 

 (1914) that pure invertase has no synthetic action. 



Whether glucose or sucrose is the first sugar to be formed 

 in photosynthesis must be regarded as an open question for 

 the present. Furthermore, it has never been proved that 

 the behaviour of all plants is similar in this respect. 



The presence of both hexoses and sucrose in the cholo- 

 plasts of the leaf of Elodea canadensis has recently been 

 demonstrated by Dixon and Mason. 



