222 Scientific Proceedings, Royal Dublin Society. 



The mean molecular weight of the dissolved substances seems to point 

 to an increase in the amount of dissolved carbohydrates as being partly 

 responsible for the rise in osmotic pressure. The dissolved substances in 

 leaves from a similar position during the month of September, 1909, had 

 a mean molecular weight of 238. This indicates a further rise in tlie 

 amount of dissolved organic constituents of the sap during the late summer. 



After the final rise of osmotic pressure in the late summer a diminution 

 in the osmotic pressure was registered in the sap from leaves just about to 

 fall. Tliis diminution may be attributed to tlie transport of materials from 

 the leaves. 



