Chap, vi The Metabolic Processes 375 



proved by Kosmann in 1877, Baranetzky in 1878, and 

 Krauch in 1879. Kosmann and Krauch detected it in the 

 leaves and shoots of the higher plants, and Baranetzky in 

 buds and potato tubers. He found it so widespread that 

 he suggested that it is universally present in vegetable 

 cells. Further researches extending our knowledge of its 

 distribution were made by Brasse in 1884. 



The existence of diastase in leaves was disputed by 

 Wortmann in 1890, and his observations led to further 

 more careful researches by Vines in 1891, and by Brown 

 and Morris in 1893. The work of the latter observers was 

 the fullest and most detailed that has at present been 

 carried out on the diastase of foliage leaves, and may be 

 regarded as establishing beyond controversy the existence 

 of the enzyme and the part it plays in the translocation 

 processes. 



Sachs, as we have seen, suggested in 1882 that the 

 migration of starch is preceded by its conversion into 

 sugar. It had been known since the early part of the 

 nineteenth century that such a conversion is easily effected, 

 and that KirchofPs extract is capable of bringing it about. 

 It was not till 1871 that the nature of the sugar resulting 

 from the action of diastase on starch was ascertained, when 

 Briicke, O'Sullivan, and Griessmeyer, working indepen- 

 dently, came to the conclusion that it is maltose. It was 

 previously known to be able to reduce Fehling's fluid. The 

 discovery of a reducing sugar in the leaf was first made 

 by Meyer in 1885. 



In their researches into the sugars of the foliage leaf in 

 1893, Brown and Morris found that the migrating sugar 

 is not maltose alone, but that glucose and fructose may 

 also be detected in the stream. As no means of preparing 

 either of the two latter from starch were then known, it 

 became evident that the translocation of carbohydrates 

 is more complicated than Sachs suspected. It will be 



