294 



Scientific Proceedings^ Royal Dublin Society. 



Table IV. 



WMaria sinensis : leaves. 



Experiments 80 and 81 were made on sap from the leaves of an old 

 Wistaria trained on a Iq-w wall. One sample of leaves was gathered from 

 short branches near the base of the main stem. The leaves were about three 

 feet over the ground. The second sample of leaves was taken from the 

 terminal branches of a stem running 65 feet approximately horizontally 

 along the wall at a level of about 3 feet. Here again we find a slight 

 difference in pressure in favour of tlie distal leaves. 



Table V. 



Ulmus campestris : leaves. 



The above experiments show the real meaning of the results which 

 apparently go to show that the level is tlie controlling factor in determining 

 the osmotic pressure. If the hydrostatic head defined the pressure of the 

 leaves, it is evident tliat the pressure of expt. 21 should be the greatest ; if 

 the resistance of the water-tracts were the controlling factor, expt. 23 should 

 have the maximum pressure, which should be much greater than 22 and 24. 

 The actual order is 24, 28, 21, 22. From this it is clear that the resistance 



