Certain Reactions of Biocollmds and Cell-masses. 69 



The uppermost line shows a sweUing in bog water equivalent to 

 that in distilled water, while the imbibition in swamp water is very 

 much less, sustaining about the same proportions as the measurements 

 of the swelling of biocolloids. The retarding action of the swamp 

 water, high in calcium, is greater than that of the solution 0.008 M, 

 in which this salt enters into nutrient solutions, and greater even than 

 that of a 0.02 M solution. The retarding action of swamp water may 

 be predicted to be about the same as a- 0.03 M solution of calcium nitrate 

 acidified as in the solution used. Such acidification was made by adding 



1 c.c. of hundredth-molar nitric acid to 25 c.c. of the calcium solution. 

 The final cessation of shrinkage and sUght enlargement of sections 



in the 2 M solution remains unexplained, since the shrinkage in a 

 solution containing but one-tenth of this amount of calcium was con- 

 stant during the entire 90 hours of the exposure. The final figures in 



2 M to 0.0002 M are of swellings which were continued for 90 hours, 

 while the swellings in water, swamp water, bog water, calcium as in a 

 nutrient solution, and acidified calcium solution were taken at the close 

 of 40 hours. The total swelling of 21 per cent in calcium nitrate 

 0.0002 M is probably equivalent to that of distilled water. The swell- 

 ings of biocolloids in the same solutions should receive attention in this 

 connection.^ 



In addition to the above note on the swelling of the sections in the 

 2 M solution of calcium nitrate, the following facts are of interest : 

 Four sections with an aggregate thickness of 37 mm. were placed in a 

 dish and covered with such a solution at the time the auxograph 

 measurements were started. As the sections under the auxograph 

 were in an expanding stage when the measurements were closed, free 

 sections were allowed to remain in the dish after the records on the 

 instrument were ended. The free sections were measured 6 days after 

 being put in the concentrated solution, with the result that their total 

 thickness was found to be 42 mm., a gain of 5 mm. or 13.3 per cent. 



Sections of a biocoUoid consisting of agar 90 parts and oat protein 

 10 parts were swelled in a series of solutions of calcium nitrate parallel 

 to the above set. The increase in the 0.5 M solution was 975 per cent, 

 525 per cent in the 0.2 M solution, 650 per cent in the 0.02 M solution, 

 1,425 per cent in the 0.002 M solution, and 1,975 per cent in the 

 0.0002 M solution. The test was repeated with the following results 

 at the end of 24 hours: swelling in 2 M solution, 917 per cent; in 0.2 M 

 solution, 722 per cent; in 0.02 M solution, 777 per cent; in 0.002 M 

 solution, 1,555 per cent. 



The minimum swelUng in this series evidently Ues between the con- 

 centrations of 0.2 M and a molar solution. 



Another series was carried out in which sections of Opuntia were 

 swelled at temperatures of 18° to 20° C. in acidified and salt solutions, 

 as given in table 58. 



* MacDougal, D. T. The effect of bog and swamp waters on swelling in plants and in biocol- 

 loids. Plant World, 21:88. 1918. 



