358 CarholnjdratcH of the Leaf of the Potato 



The views we put forward are in accord with modern views, based 

 largely on the work of Abderhalden and his school, as to food assimila- 

 tion by animals ; in all cases it is necessary for such food, for example, 

 proteins, to be broken down by enzymes into its simplest components 

 or "Bausteine," which are then taken up by the difierent cells or tissues 

 and synthesised afresh. 



The theory we have given of the method by which starch is broken 

 down in the leaf would lack justification unless definite evidence of the 

 presence of maltase in leaf tissue could be brought forward. At the 

 suggestion of one of us, Mr A. J. Daish has made a special study of this 

 question. In a series of experiments, details of which will be published 

 later, he has found that maltase is always present in the leaf tissue he 

 has examined when starch is also present. Little doubt therefore can be 

 entertained of the correctness of the view we put forward that starch 

 is broken down in the leaf to dextrose. The fact that maltose can 

 never be detected either in the leaf or stalks of plants points to the 

 amount of maltase always being in relative excess in the cells where 

 the starch degradation actually occurs, so that it is able to deal instantly 

 with the whole of the maltose formed from the starch. The fact that 

 maltose, unlike cane sugar, never occurs in the stalks or conducting 

 vessels is probably due to the fact that maltase is an intracellular 

 enzyme and apparently acts in close collaboration and in the immediate 

 proximity of the ordinary diastase which first attacks the starch in the 

 cells where this substance is stored. 



Cane sugar is apparently the first sugar formed in the potato leaf and 

 is transformed into hexosesfor translocation. 



The most striking point which appears when the analyses of the 

 potato leaves and potato stalks are compared (see Tables I and II) is 

 that whereas the saccharose is greatly in excess of the hexoses in the leaf, 

 the reverse is true in the stalks. These results are exactly similar to those 

 obtained with the mangold leaf in the early stages of growth (Series I), 

 a fact which points to the mechanism of formation and translocation 

 being the same in both cases. Saccharose is probably the first sugar 

 formed in the mesoph yll of the leaf ; it is gradually inverted on its way 

 through the veins, mid-ribs, and stalks, the inversion becoming more 

 and more complete as the root or tuber is approached. In this series 

 of pickings it must be borne in mind that the "stalks" were mainly 

 those bearing the small leaflets and did not include any of the stem 



