THE CARBOHYDRATES OF THE ANGIOSPERM LEAF 9 



to hydrolysis of sucrose, the glucose produced by that 

 reaction having been largely used in respiration. To test 

 this latter point they record two sets of analyses of leaves 

 picked after a bright warm day a, dried at once; and 6, 

 kept in the dark for twenty-four hours with petioles in 

 water. One of these tables is quoted below : 



TABLE III. 

 CARBOHYDRATES IN TROP^EOLIJM LEAF. 



a. b. 



Starch 5-425 0-906 



Sugars : 



Sucrose 7-33 3-35 



Glucose 0-00 1-34 



Fructose 2-11 3-76 



Maltose 2-71 1-28 



Total sugars per cent. . . 12-15 9-73 



Total loss of sugars and starch in & = 6-93 per cent. 



The great loss in carbohydrates experienced by the leaves 

 kept in the dark is accounted for as due to the respiration 

 of the cells. In addition the relative amounts of the 

 carbohydrates have altered considerably. The loss has 

 fallen chiefly upon the starch, though sucrose and maltose 

 have sunk to less than half their original quantities. On 

 the other hand, both glucose and fructose have increased. 

 Thus, during darkness starch is hydrolyzed to maltose, and 

 finally to glucose, which, together with glucose and fructose 

 obtained by the inversion of sucrose, is used for respiration 

 The accumulation of fructose in excess of glucose points to 

 the latter as being respired or used for tissue formation 

 more readily than the former. 



Previous work by these authors (1890) had shown that 

 sucrose far surpasses all other carbohydrates in bringing 

 about starch formation, when it is used as a nutrient for the 



