METABOLISM AND GROWTH 215 



transformation of the starch into sugar was at once 

 made the subject of investigation, with the result that 

 the enzyme " diastase/' identified in 1833 by Pay en and 

 Persoz in germinating barley, was discovered in the 

 leaf, and further that the sugar formed by its action 

 was maltose. Brown and Morris, in 1893, went further, 

 and claimed that glucose and fructose were also produced, 

 and they thought that these two sugars arose from cane- 

 sugar as the result of the action of another enzyme, 

 " invertase," cane-sugar being, according to the authors, 

 the first sugar to be formed in the leaf. 



The anabolism and transport of proteins were also 

 studied by many workers during the period 1860-80. 

 Chief among these was Pfeffer, who detected amino- 

 compounds in the descending sap, and Vines, who deter- 

 mined the presence of proteolytic enzymes in the leaf. 

 Another problem that exercised the minds of physiologists 

 in the same years was the exact path by which these 

 soluble carbohydrates and proteins travelled. Sachs 

 at first thought that the cortex was responsible for the 

 transport ; Haberlandt suggested the laticiferous tubes ; 

 Schimper claimed that the sheath of the vascular bundles 

 was the medium, and Strasburger, Kraus, and others 

 attributed the duty of translocation to the sieve-tubes 

 of the phloem. How translocation was actually brought 

 about, and what were the effective forces concerned, 

 remained quite in doubt up to the end of the century. 



Meanwhile much work had been accomplished on the 

 products themselves. To start with, Schimper in 1880, 

 Meyer about 1885, and, eight years later, Brown and 

 Morris worked out the whole history of starch as a reserve 

 substance, its origin from chloroplasts and amyloplasts, 

 its dissolution by enzymes, and its transportation and 

 re-deposition. In 1895 Meyer summarised all that was 

 known on the subject, and cleared up some controversial 

 points left unsettled by his predecessors. Although 

 in the great majority of cases the carbohydrate reserve 



