104 Hydration and Growth. 



which for the present may be ascribed in part to the fact that generaliza- 

 tions on permeability rest upon results obtained with a narrow range 

 of material or under highly specialized conditions. It would seem 

 allowable to assume, if antagonistic effects are to be attributed to 

 the opposed action of two salts, that sections of living plants would 

 show differentiating swelling capacities in balanced solutions and in 

 their two components. The first trial of this matter was made with 

 terminal internodes of Mentha spicata, which had attained about half 

 of their final length and had an average diameter of 3 mm. The 

 imbibition capacity of this plant in living and dried conditions has 

 been described elsewhere in this paper. An estimation by Professor 

 H. M. Richards made the approximate acidity of the "pure juice" 

 such that 1 c.c. = 0.45 c.c. N/20 KOH, and that the total acidity of a 

 gram of fresh material was equivalent to 0.64 c.c. N/20 KOH. 



A few simple tests were planned which might furnish results having 

 a bearing upon the present question. The neutralizing or balancing 

 action of sodium and calcium being one of the commonest conjunctions, 

 the action of these two elements in the form of chlorides were tried. 1 



The balanced solution, consisting of 100 parts of 0.375 M sodium 

 chloride and 10 parts 0.195 M calcium chloride was used. Such a 

 solution plasmolyzes cells of Spirogyra, but according to Osterhout's 

 findings, the presence of two salts in the proportions given prevents 

 either from passing the membrane. It would appear that Osterhout 

 in later papers takes the position that the essential feature of antagon- 

 ism between two substances consists in the fact that they produce 

 opposed effects upon it. 2 



Sections of stems of Mentha, as described above, swelled about 

 0.075 mm. in distilled water, shrunk 1 mm. in the balanced solution, 

 but came back to a volume slightly greater than the initial size when 

 distilled water was run into the dish. The shrinkage in the solution 

 of sodium chloride, 0.375 M, was very marked, dilution being fol- 

 lowed by a resumption of the original volume. Similar effects were 

 obtained with the solution calcium chloride. 



The terminal parts of growing stems of an Erigeron, which were 

 higher in acid than Mentha, were next tested. The sections had a 

 diameter of about 3.7 mm. and included a length of 5 to 7 mm. of the 

 stem. The balanced solution and its constituents were diluted to 

 one-thirtieth of the above concentration to avoid shrinkage by plas- 

 molysis. The swelling in distilled water (average of 3 sections by 

 auxographic method) was 0.2 mm.; in the balanced solution, 0.15 

 mm.; in sodium chloride (6 sections), 0.2 mm.; and in calcium chlo- 

 ride (6 sections), 0.15 mm. These minute swellings progressed for a 



1 Osterhout, W. J. V. The permeability of living cells to salts in pure and balanced solutions. 

 Science, 34: 187-189. 1911. 



2 Osterhout, W. J. V. Nature of antagonism. Science, 41 : 255-256. 1915. 



