Dixon and Atkins — Osmotic Pressures in Plants. 



455 



electrolytes is the same iu the thick and tliin roots. A steady rise in 

 this concentration np to August is indicated, and a decline from that into 

 the winter. 



As in the leaves, the major part of the osmotic pressure is due to the 

 carbohydrates. The great rise in the late summer is also due principally to 

 the storage of carbohydrates, but in part to a concentration of electrolytes. 



Ilex aquifolium. —Roots. 

 Fig. 3. 



As is often the case with the leaves, age leads to an increase in osmotic 

 pressure ; but, whilst this increase in the case of the older leaves is due to tlie 

 accumulation of electrolytes, all the evidence goes to show tliat the higher 

 pressure of the older roots is due to the storage of carbohydrates. 



4c2 



