THE CARBOHYDRATES OF THE ANGIOSPERM LEAF 7 



sugars glucose, ^-fructose, sucrose, and maltose. Two 

 separate analyses of the dried leaf gave the following results : 



TABLE I. 



PERCENTAGES OF SUGARS IN TROP^IOLTJM LEAF, CALCULATED ON THE 

 DRY WEIGHT. 



a. 6. 



Sucrose 3-24 3-39 



Glucose (dextrose) \ /2-41\ /) _ a 



i-Pructose (levulose)/ \2-18 j 4 ' 59 



Maltose 0-76 0-61 



8-69 8-59 



This table shows the nature of the accuracy to be expected 

 in other analyses. 



The presence of maltose was proved not only by the 

 analytical details of the sugar determinations, but also by 

 the preparation of its characteristic osazone, and by the 

 determination of the nitrogen content of the latter. The 

 increase in reducing power of the mixture of sugars, when 

 treated with maltase after previous complete inversion 

 with invertase, affords additional evidence of the existence 

 of maltose in the leaf, for maltase has no hydrolyzing action 

 on any carbohydrate other than maltose. 



CHANGES IN CARBOHYDRATE CONTENT DUE TO INSOLA- 

 TION. The diurnal changes in the carbohydrate content 

 may be seen from Table II., in which under a is given 

 the analysis of leaves picked from the plant at 5 a.m.; 

 under b, that of leaves plucked at 5 a.m., and insolated 

 with their petioles in water till 5 p.m.; and under c that 

 of leaves plucked at 5 p.m. The day chosen was fairly 

 bright and sunny. 



It will be noticed that the amount of starch in the cut 

 leaves, has not increased to so great an extent as in 

 those attached to the plant, though the sugars have 

 increased very markedly. This result was always obtained 



