Influence of Certain Carbohydrates on Green Plants 63 



and this expectation has been reahzed. Throughout the experiments 

 recorded in this paper a tendency to anthocyan production was noted, 

 and in some cases briUiant red pigmentation was produced in the stems 

 of vetch. In one experiment with vetch in which 0.05 molecular solution 

 each of glucose and of maltose was used, at the end of two months the 

 maltose-feel plants were colored throughout, the glucose-fed plants were 

 colored to within half the distance of the top, and the control plants 

 grown in the absence of sugar were entirely lacking in the pigment. The 

 color disappeared in the course of a week on transferring the plants to 

 the laboratory, where a diffuse light prevailed. The same loss of pig- 

 ment was observed in other cases when the plants were transferred from 

 the greenhouse to the laboratory. It was also noted that during periods 

 of cloudy weather no pigment developed in plants grown in the greenhouse. 

 No marked difference was noted in the production of pigment by the 

 different sugars. Lactose, however, appeared to be the least beneficial, 

 although in one experiment with vetch this was not the case. The subject 

 is to receive further attention. 



GENERAL DISCUSSION 



In a consideration of the increased yields of plants grown in the presence 

 of sugars, it should be borne in mind that undoubtedly greater increase 

 would have been attained had the plants been grown with their tops 

 exposed to the atmosphere instead of being inclosed within a glass chamber. 

 As already pointed out, the cotton plugs cause a retardation in the 

 diffusion of carbon dioxide- into the plant chambers. In the smaller 

 tubes this is probably fully counterbalanced by the increased rate of 

 production of carbon dioxide in the sugar-fed plants. The increased 

 gain of these plants is due, therefore, not alone to the absorption and 

 assimilation of sugar, but in part to their having a greater supply of carbon 

 dioxide — produced, it is true, through the increased respiration of the 

 plant — which carbon dioxide diffuses outward with difficulty owing to 

 the presence of the cotton plugs. 



The increases effected by the sugar, furthermore, are not so great 

 as those obtained by Maze (1889), by Maze and Perrier (1904), and 

 by J. Laurent (1904), because of the fact that the plants were grown 

 entirely within the closed chamber. The atmosphere of the chamber 

 was constantly of a high relative humidity, and consequently transpiration 



