352 MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 



lead to any simplification of the major processes under discussion. 

 The advance is in a diametrically opposite direction. Newly 

 determined features of carbohydrate metabolism included in respi- 

 ration and necessary for growth and functionation have been found 

 to be extremely complex. Imbibition in the plant is not that of a 

 single colloid, and swelling is not the simple resultant of the action 

 of two or more substances. The interaction between two emulsoids 

 presents many possibilities. The proteins viewed physiologically 

 appear to act as " sensitizers " to the carbohydrate gels which make 

 up the greater part of the bulk of the protoplast, and to produce in 

 them highly specialized effects with acids, alkalies and neutral solu- 

 tions. The general character of respiration, and the nature and 

 amount of its by-products acting upon a "sensitized" protoplastic 

 gel may be taken to determine the general aspect, rate, course and 

 amount of growth in plants. 



