136 D. T. MacDOUGAL and h. a. spoehr 



of 16 to 18°C. at which swellings under instruments were also 

 made. At the end of twenty-four hours the mucilaginous solu- 

 tion was measured off, 50 cc. being allotted for acidity determi- 

 nations (see results above), and 180 cc. was used for determi- 

 nation of the solid matter present. It was found that this 

 amounted to 0.28 gram for the 240 cc. of juice obtained from 

 sections having a total volume of 40 cc. when fresh. The actual 

 solid matter of the sections including the cell walls may be taken 

 as 10% of the whole, or as 4 grams. Of this 7% was dissolved 

 out in water. 



The extraction of this amount of material could readily be 

 held to account fully for the changes which take place in 

 hydration and which give different expansions in the second 

 immersion. 



According to recent results of Miss E. Grace Stewart, the 

 pentosans which are probably present in all cells in varying 

 proportions are formed in the cytoplasmic mass, and collect in 

 a layer near the wall or in cavities in the protoplasm. 5 The 

 bursting of some cells by imbibition pressure or the crushing of 

 others in preparing the sections allows some of this material to 

 escape in extractions or in swelling. 



It is to be noted that we purposely avoid all mention of 

 osmotic action in the obvious sense. Swelling may in the ulti- 

 mate be due to the increase of internal microns in colloids of 

 plates, of cells and of dried tissues by the adsorption of mole- 

 cules of water and hence the differential between this increase 

 and the loss by migration and dispersion of salts, acids and 

 colloidal material might be regarded as the resultant of osmosis. 



It is quite clear that no explanation of absorption of solutions 

 by cell masses, or of plasmolysis may be adequate or greatly 

 useful which does not take into account certain fundamental 

 mechanical features of the cell-structure. Among these are to 

 be included the phase boundaries of the colloids of the cell wall, 

 of the vacuoles, of the protoplast, and of the multiple and 

 varying structures in the protoplasm. Some recognition of 



5 Stewart, E. G. Mucilage or slime formation in the cac.ti. Bull. Torr. Bot. 

 Club 46- 157. 1919. 



