OSMOTIC PRESSURE IN PLANTS 83 



complexes are known to occur. On the whole, however, 

 it cannot be regarded as at all well established. 



The theory which has been found to command the 

 greatest degree of credence is that which considers the 

 membrane as a solvent, permitting the passage- of those 

 substances which are soluble in it. Though propounded 

 as far back as 1855 by L'Hermite, it has only come into 

 prominence comparatively recently through the work of 

 E. Overton (1895) and others. 



