Influexce of Certain Carbohydrates on Green Plants 65 



in hydrate form. The latter result has been noted in the Laboratory 

 of Plant Phj'-siology at Cornell. 



iMolliard (1907) beheves that there is an antagonism between the 

 absorption of sugar and chlorophyll function, with the result that injury 

 is done to the plant. He states that there would be inverse currents 

 of sugar, and, as he says, one can conceive that the two currents are 

 injurious. MoUiard's conclusions are based on two different series of 

 experiments. In one series the plants were grown in tube cultures — 

 in the fu'st case with normal air, in the second case with 10 per cent of 

 carbon dioxide, and in the third case with 10 per cent of carbon dioxide 

 and glucose. The plant grown in 10 per cent of carbon dioxide gained 

 48 milligrams, while the plant grown in 10 per cent of carbon dioxide 

 and glucose yielded only 32 milligrams dry weight; the control plant, 

 gi'owing -without sugar and in normal air, yielded 16 milligrams dry weight. 

 IMolliard considers that " the poorer growth of the glucose-fed plant is 

 caused by an antagonism between the assimilation of carbon dioxide 

 and the absorption of sugar. A more probable explanation is that the 10- 

 per-cent carbon dioxide content is augmented by the increased respiration 

 of the culture plants during the night, and that in the early stages of 

 growth the air has constantly a higher concentration than 10 per cent 

 of carbon dioxide and this increase may be injurious to the culture plant. 

 The results of the experiments on respiration show that carbon dioxide is 

 constantly eliminated during the daji:ime in the first sixteen days of ^ 

 growth. 



In Molliard's second experiment the growth in open and in closed tubes 

 was compared. Three plants were growm for two months in open tubes 

 on 1-per-cent glucose. At the end of two months two of the tubes were 

 sealed and the third was left open, but plugged with cotton. Six weeks 

 later the weight of each plant was determined, with the following results : 



Fresh 



weight 



(milligrams) 



Dry 



weight 

 (milligrams) 



Ratio of 



dry weight 



to fresh 



weight 



Tube open . 

 Tube closed 

 Tube closed 



907 

 1,427 

 1,747 



122 

 212 

 231 



0.134 

 0.148 

 0.134 



