COLLOIDAL BEHAVIOR OF PLANT PROTOPLASM. 157 



would furnish conditions parallel to those in the plant, but the in- 

 fluence of changing proportions of the pentosans to the other cell- 

 contents has been followed through the season by analyses in the 

 chemical laboratory and by swelling tests of living and dried sections 

 of the plants.^ 



Next to the composition and to the condition of the components, 

 the matter of greatest importance is that of the ions or substances 

 which may determine the course and amount of hydration. Acids, 

 hydroxides and amino-compounds are to be included in a list of the 

 substances of physiological importance. The action of hydrogen 

 ions, of hydroxyl ions and of ions which may be derived from amino- 

 compounds in the way of accelerating or retarding hydration may 

 be shown by expressing the swelling values produced in terms of 

 those obtained in water taken as lOO given in Table II. 



TABLE II. 



Hydration of Colloids in Hydrochloric Acid, Potassium Hydroxid and 

 Glycocoll at o.oi N with that in Water as ioo. 



- MacDougal, D. T., " Hydration and Growth," Publ. 297 Carnegie Inst, 

 of Wash., 1920, p. 132. 



