56 



Scientific Proceedings, Royal Dublin Society. 



pressure than the lower portions of the stem, the minimum lying at the 

 4-metre level. In the early spring the gradient from root to summit is 

 unbroken, and the same is true in the late spring. The greatest pressures are 

 found in early spring. 



The electrical conductivity measurements do not show such a degree of 



Height above ground-level in metres. 



regularity as the osmotic pressures, but in a general way they follow the latter 

 in autumn, inasmuch as the root and summit are higher than the 4-metre 

 level, which is a minimum value. In early and late spring there is a marked 

 rise in conductivity, the April measurements being on the whole considerably 

 higher than those of February. 



The key to the whole series of changes is, however, obtained by examining 

 the values of A - A e , which indicate the depressions of freezing-point due to 



