Dixon and Atkins — On Osmotic Pressure in Plants, ^c. 293 



encountered difBculties and left tlie question undecided. In our experiments 

 sap was pressed from leaves taken at a considerable height above the ground ; 

 and its freezing-point was compared with that of leaves from near the ground- 

 level. The following pairs of experiments bear on this question. 



Table III. 



It here appears that, on the whole, taking the experiments in pairs, the 

 leaves at the lower level contained sap with a lower (sometimes considerably 

 lower) osmotic pressure than that of higher leaves. But the experiments are 

 far from satisfactorily bearing out this view ; for it will be noted that the 

 osmotic pressure of the sap from leaves at the same level, but at different 

 times and under different conditions, by no means corresponds in each case, 

 although it is often higher than that of leaves at a lower level. The reverse, 

 however, is sometimes found, as in expt. 6 and 7, where the pressure in 

 the lower is much greater than in the higher leaves. 



The possibility that these discrepancies might be due to resistance in the 

 conducting tracts apart from that offered by the hydrostatic head had to be 

 examined, and experiments 80, 81, 82, 83 on Wistaria sinensis a.n(i.2\, 22, 

 2'6, 24 on Vlnms catnpestris were carried out. 



3a2 



