66 Lewis Knudson 



It will be noted that there was increased gain in the closed tubes. 

 MoUiard explains the increase here as due to the fact that the assimilation 

 of carbon dioxide was prevented and consequently its injurious action 

 was eliminated. A more probable explanation, in the writer's opinion, 

 is that the plants in the closed tubes had a greater carbon dioxide content 

 available than those in the cotton-plugged tube. 



As was brought out in the respiration experiments with vetch, a constant 

 elimination of carbon dioxide occurs in the sugar-containing cultures. 

 This carbon dioxide is undoubtedly assimilated, and it is fair to assume 

 that the carbon dioxide produced in respiration in darkness and in the 

 constant respiration of roots affords a supply of greater concentration 

 than that furnished by the normal atmosphere. The writer attempted 

 experiments to test the contention of Molliard, but in each of the several 

 experiments set up complications interfered with the results. In two 

 experiments the plants grown in closed chambers with glucose supplied 

 showed less gain than the plants grown in open chambers with air avail- 

 able. The plants were grown for only twenty days, however, and the 

 experiments were necessarily stopped in each case because of the appear- 

 ance of molds. 



Lindet (1911) has stated that fructose induces tissue formation in plants, 

 while glucose is utilized largely in respiration. He found that yeasts, 

 Penicillium glauQum, Aspergillus niger, and the embryos of bean and 

 barley, were influenced similarly by glucose and fructose. Glucose was 

 more readily absorbed than fructose, but contributed largely to respira- 

 tion. Fructose, on the other hand, in all cases increased the dry weights 

 of the plants much more than did glucose. No cases similar to these 

 have been noted in the writer's experiments, though the superiority of 

 saccharose for vetch and peas may be explained by the work of Lindet. 

 This subject of the role of glucose and fructose is now being intensively 

 studied in the Laboratory of Plant Physiology at Cornell. 



It has been demonstrated conclusively that various sugars can be 

 absorbed by the roots of green plants and that these sugars are assimilated. 

 Not only can sugars be absorbed and assimilated, but investigations 

 show that methyl alcohol, glycerin, certain organic acids, and various 

 organic nitrogenous and other organic substances, may likewise be uti- 

 lized. The practical significance of these facts is inmiediately questioned. 



