Let me dwell for a moment on this result, for, al- 

 thougfh it may be somewhat foreign to our present pur- 

 pose and to the further observations of Haberlandt, it is 

 very significant in itself. The water moves in the plant 

 in closed cells, as the cells of the aqueous gland are entirely 

 closed, but the organic membrane, as every one knows, has 

 the peculiar physical property of allowing water to pass 

 through, the pressure, of course, being applied on the side 

 of least resistance; when therefore the water is forced into 

 the cells by root-pressure, it is easily intelligible that ac- 

 cording to purely physical laws it should come to the 

 surface of the leaf on the side of the least resistance, that 

 is, by way of the water-crevices. Even the defenders of 

 "vital force" would not find any reason in this for not con- 

 sidering the phenomenon of distillation in this case a 

 purely physical phenomenon. And still according to 

 Haberlandt's experiments it is not. The sublimate could at 

 most only impede the process of filtration, but should under 

 no circumstances have destroyed it. But it does destroy 

 it, and the hydathode dies. The conclusion certainly fol- 

 lows from this that this process is connected with some 

 vital function. Even if the hydathode is treated with sub- 

 limate solution, all the conditions for mechanical filtration 

 still remain: the earth has moisture which can be taken up 

 by the roots so that root-pressure still exists. The water 

 is in all cases conveyed to the hydathodes through the 

 vascular fibres, the cell walls of the hydathodes are still 

 adapted for filtration, and yet they do not filter. Hence 

 some other factor must join itself to the physico-mechanical 



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