iQoo-i.] Effects of Water on Foliage Leaves. 269 



substance in solution is largely in the same condition as when found in 

 the xylem of the root. So we have in the leaf an alkaline liquid on its 

 way towards the minute tracheids entering into whatever chemical 

 compounds are natural to the leaf. The alkaline substance which 

 diffuses out through the leaf surface to the distilled water is not in all 

 likelihood zvJiolly the same as that coursing upward through the 

 conducting vessels, for there diffuses out through the leaf, potassium 

 oxalate, a compound organic in its nature, and one which therefore has 

 had to do with the plant metabolism. Sachs shows that the liquid in 

 the xylem of the roots is alkaline and that this alkaline quality is 

 maintained throughout its course into the leaf. 



To sum up, one may conclude from these experiments and from 

 those recorded in Chapters III. and IV., that a substance is extracted 

 from leaves of plants by the application of distilled water, and that this 

 substance gives generally an alkaline reaction. This alkaline reaction 

 is produced largely by compounds of potassium (potassium carbonate 

 and potassium oxalate). If distilled water extracts salts from leaves it 

 may be that rain-water does, and this will result in a loss of substance 

 to the leaf If the substance be injurious to the plant this process 

 might be called 2i process of excretion. The amount which diffuses out 

 differs with different plants, and the alkaline reaction may be masked by 

 the presence of other substances as shown above. It has been shown 

 that, in the case of the potato plant (1895), distilled water when applied 

 to the leaves, acts as a stimulus to growth, and the suggestion is here 

 offered that the stimulus may be a result of the loss of injurious salts 

 which had accumulated in the leaves, the removal of which substances 

 would benefit the plant. 



VI. — The Effects of a Nutkient Solution and of 

 Distilled Water upon Leaves of Plants. 



The experiments here described in detail were designed to extend at 

 intervals over a period of two years, and to have the plant as nearly as 

 possible under natural conditions. It was expected that these investi- 

 gations would throw some light upon the much disputed question as to 

 whether leaves can absorb water and solutions to the advantage of the 

 plant. x'\rrangements were made to have the roots of the plant isolated, 

 so to speak, from the atmospheric conditions surrounding the leaves, and 

 to have the roots supplied with nothing but distilled water and air. It 

 was thought that if no food were supplied to the roots, growth could not 



