3.')f> Carholtydrates of the Leaf of the Potato 



9-9 per cent. ; this is still considerably lower than the values we have 

 found. Kluyver [1914] recently on repeating Brown and Morris' 

 experiments with Trofceolum, but using a new biochemical method of 

 estimating the hexoses, saccharose and maltose^, based on the differences 

 in the amount of carbon dioxide evolved on fermenting the solution 

 with special torulae and with ordinary yeast, also found in :ill cases 

 relatively very small amounts of maltose. Thus in one ca.se, which is 

 of special interest because the hexoses and cane sugar are nearly 

 identical with values found by Brown and Morris, Kluyver found in 

 leaves plucked at 2.30 in the afternoon, hexoses = 5-2 per cejit., sac- 

 charose = 4-6 per cent., maltose = 0-3 per cent. ; this compares with Brown 

 and Morris' analysis, hexoses = 5-6 per cent., saccharose = 4-9 per cent., 

 maltose = 1-2 per cent. In the remaining cases which Kluyver cites the 

 results are given merely relatively, without calculating back on the dry 

 matter of the leaf: but, in every instance, the proportion of maltose 

 found was exceedingly small as compared with the saccharose and 

 hexoses. Thus, for example, a sample of Tropceolum leaf picked at 

 4 p.m. on July 28th, and tlierefore corresponding with an analysis in 

 which Brown and Morris found saccharose 8-02 per cent., maltose 3-62 

 per cent., and in which maltose formed 27-5 per cent, of the total sugars, 



gave 



Saccharose ... 25-8 mgrms. 



Hexoses ... 21-8 ,, 



Maltose ... l-O „ 



The maltose found here forms only 3-2 per cent, of the total sugars. 

 In Brown and Morris' experiments the maltose always appeared to be 

 at a maximum at the end of the afternoon, that is at the same time as 

 the starch reached its highest values ; for example, in one case (p. G69) 

 a leaf picked at 5 p.m. when the starch formed 4-59 per cent, of the dry 

 leaf, maltose was found to be present to the extent of 5-33 per cent., 

 and to form 56 per cent, of the total sugars. 



These results are fundamentally different from Kluyver's obtained 

 at the same time of day and the difference is probably to be explained 



^ Torula monnsa does not contain tho enzymes maltase and invertase, and hence is 

 capable of fermenting tlio hexoses only, leaving the maltose and saccharose unchanged; 

 Torula daitila contains invertasc but not maltase, and therefore ferments cane sugar and the 

 hexoses but not maltose. I)r A. J. Kluyver has been kind enough to send us pure cultures 

 of these Torulae, wliich l)r H. Limbosch has tested for us in our laboratory, according 

 to our own methods of working, on very carefully purified specimens of sugars. We 

 can confirm Kluyver's statements as to the specific nature of these organisms which 

 should prove of considerable service in sugar analysis of the kind we have had to dial with. 



