STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



61 



plants. Its solution is associated with the extraordinary difficulty 

 of quantitatively determining the various sugars in leaves which 

 have been subjected to a series of experimental conditions. 



Table 42. 



Unfortunately the results of experiments which we have carried 

 out with this problem in view had to be discarded on account of 

 some uncertainties which developed later in our analytical methods. 

 However, the investigation of this phase of the carbohydrate econ- 

 omy problem is to be continued. 



Table 43. — Rate of emission of CO2 hy 7 leaves of Helianihus annuus nl 25°. 

 Petioles in nitrogen-free nutrient solution containing 7 per cent d-levulose and 0. 1 1 per cent 

 glycocoll. CO2 absorbed in Ba(0H)2 solution, 0.11835 normal, 125 c. c. of which has the CO2 

 equivalent of 0.3254 gram CO2. 



In the three following experiments d-levulose was used as the 

 sugar in the nutrient solution. The first of these was carried out 

 with d-levulose as the only organic substance in the nutrient solu- 

 tion. The analytical data of the changes of materials in the leaves 

 are given in table 40. 



These leaves also showed the usual gain in amino-acids after 

 remaining 76.75 hours in the dark. There was, however, a decrease 



