266 Scientific Proceedings, Royal Dublin Society. 



in plants can only be made when the conditions governing the permeability 

 of plant cells are better understood. 



SUMMAEY. 



Branches of Tilia americana and Samhucus nigra were enclosed in a strong 

 cylinder in such a way that their cut ends protruded. Compressed air at 

 pressures up to 20 atmospheres was admitted into the cylinder, and the liquid 

 which exuded from the cut end of the branch was collected. This liquid 

 was found to be completely, or almost completely, free from sugars. Experiments 

 carried out in early and late summer gave similar results. After the leaf cells 

 had been made permeable by means of toluene vapour the sugar in the expressed 

 sap amounted to about 5 per cent. 



Eeferences. 



1. Dixon, Heney H. — The transport of Organic Substances in Plants. 



Presidential Address, Section K, British Association, 1922. 



2. Dixon, Henry H. and Ball, Nigel G. — Transport of Organic Substances 



in Plants. Nature, Feb. 23, 1922. 



3. Dixon, Henry H. — On the Osmotic Pressure in the Cells of Leaves. Proc. 



Royal Irish Academy, 1896, Vol. IV, ser. 3, p. 61. 



