COLLOIDAL BEHAVIOR OF PLANT PROTOPLASM. 151 



closing and boundary layers of nuclei and of all special bodies in the 

 protoplasm would have a similar dual origin. 



V. Highly proteinaceous plasmas would form external layers, 

 which in conformity with the above, would not be cellulose or so 

 high in carbohydrate. The chitinous skins of some animal organ- 

 isms ofifer an inviting subject for examination in this connection. 



VI. In so far as these limiting layers offer resistance to the 

 passage of substances in solution equally in both directions, or as 

 they allow the free passage of water and resistance to substances in 

 solution, they form an osmotic machine by the action of which 

 pressures may be set up internal to the cell and to plasmatic or 

 nuclear masses. The implied phenomena designated as turgidity 

 are most marked in plant cells where distentive forces of 40 or 50 

 atmospheres are found. It is to be noted also that when the two 

 elements of a plasmatic colloid, the carbohydrate and the albumin, 

 are unequally hydrated, as is the case in nearly all solutions, the 

 superior increase of one element in the complex meshwork would set 

 up something akin to osmotic pressure. 



VII. Hydration increases or swelling is the result of the com- 

 bination of molecules of water with colloidal aggregates of the mass. 

 The addition of any substance which forms combinations with the 

 colloidal carbohydrate or protein may give systems which attract, 

 combine with and hold proportions of water different from those 

 displayed when water only is present. 



VIII. The hydration increase or swelling of an intermeshed 

 pentosan-protein colloid, such as we imagine protoplasm to be, in- 

 volves the possibility of the unequal increase of these two main com- 

 ponents under the influence of any substance or ion, and the measur- 

 able alterations in volume will be the resultant of the eft'ects of such 

 a substance or ion upon the hydration of the unlike components. 



IX. The pentosans are weak acids and in general their hydration 

 capacity is lessened by hydrogen ions. Hydroxyl ions and com< 

 pounds containing the amino-groups, such as may be in solutions 

 of phenyl-alanin, alanin, asparagin and glycocoll, may exert an effect 

 by which hydration capacity is increased above that in pure water. 

 Mucilages derived from various sources show some differences in 

 reactions to the solutions named while conforming to the generaliza- 



