Certain Reactions of Biocolloids and Cell-masses. 73 



The swelling of sections of agar plates 0.2 mm. in thickness at 15° C. 

 resulted in increases of: 



Table 66. 



p. ct. 



Distilled water 700 



Bog water 650 



Swamp water 425 



Nutrient solution, 0.6 per cent 375 



It is to be seen that all of the solutions decrease the swelling capacity 

 of the agar below that displayed in distilled water, and that the greater 

 reduction in the nutrient solution is to be attributed to the higher salt- 

 content. 



Plants of bogs and especially swamps are undoubtedly subjected to 

 great variations in the composition of the water by reason of inunda- 

 tions and floods. It was thought pertinent to extend experiments 

 in which alternations of solutions were made in such manner 

 as to test the effect of previous history on the behavior of a bio- 

 colloid. Sections of agar-oat protein 0.18 mm. in thickness swelled 

 972 per cent in 12 hours at 17° to 19° C. and reached a total of 1,233 

 per cent at the end-point in 108 hours, which are equivalent to results 

 previously attained and hence afford a fair basis of comparison with 

 the following, in which a trio of sections swelled 2,361 per cent in dis- 

 tilled water at the end-point in 72 hours. Replacement of distilled 

 water with swamp water was followed by a slow shrinkage, but this 

 amounted to only 36 per cent of the original volume. No swelling 

 agent yet tested has been found to reverse the action of another solu- 

 tion so fully as to bring the dimensions of the sections down to the 

 dimensions which might be attained in the second agent alone. 



Sections of a biocoUoid consisting of 90 parts agar and 10 parts of 

 bean protein to which 0.8 per cent of nutrient salts had been added, 

 0.18 mm. in thickness, were now swelled in swamp water at 18° to 

 20° C. The increase was measured at the end of 16 hours, at which 

 time the total swelling was 1,082 per cent. The swamp water was 

 now replaced with hundredth-normal citric acid-potassium nitrate for 

 36 hours, during which time no appreciable change was registered. 

 Replacement of this solution with swamp water was followed by a 

 resumption of the swelling, which carried the thickness of the sections 

 to 1,388 per cent of the original, which is greater than that attained 

 in the simple continuous swelling in swamp water. 



Swamp water is high in salts, and it is probably this feature to which 

 its influence on swelling is due. A test parallel to the above was made 

 in which the sections were first swelled in a 0.5 per cent nutrient solu- 

 tion in which the salts are somewhat more concentrated than in the. 

 swamp water. A swelUng of 888 per cent took place in 17 hours, at 

 which time the pen of the auxograph was tracing a horizontal line. 

 Replacement of the nutrient solution with the acidified potassium- 



