Effect of Salts and Acids on Biocolloids and Cell-masses. 



39 



Briefly summarized, agar takes up the greatest amount of water in 

 24 hours from a 0.05 N solution, and the maximum imbibition in 

 gelatine and gelatine-agar combinations also ensues in this concentra- 

 tion, which is one duplicated in the cell-masses of the plant. Cotyl- 

 edons and sections of the plants tested found their maximum at a 

 concentration of 0.1 N at the temperatures named. 



Hydration of dried plates, or of sections of living plants, is, of course, 

 accompanied by a diffusion or solution out of the contained salts in a 

 manner determined by a large number of environmental conditions, 

 inclusive of the proportionate amount of water to which the colloid is 

 exposed or in which it may be immersed. 



Thus, in most of the experiments described in this volume, the sec- 

 tions having a total initial volume of dried material of about 2 or 3 

 c. mm. were immersed in dishes containing 33 c. c. of water. The 

 hydration of material over a period of 24 to 50 hours would necessarily 

 result in the solution out of a portion of the salt contained, which might 

 form as much as 18 per cent of the original dried weight of the sec- 

 tions. On the other hand, swelling in a solution of salt-free colloid, 

 for example, might result in an accumulation. 



A series of tests was made to ascertain the relative amounts of water 

 which might be taken up by one of the biocolloids used extensively in 

 this work from a graded series of a salt solu- 

 tion. Since it showed a maximum hydration 

 capacity at temperatures of 15 to 40 C., a mix- 

 ture of agar 90 parts and oat protein 10 parts 

 was used, and the sections, which ranged from 

 0.16 to 0.18 mm. in thickness, were measured 

 as to each set and arranged in trios in glass 

 dishes. The sections were as nearly uniform as 

 possible and the average volume of the air-dry 

 trios of sections in each dish was 12 c. .mm. 

 The testing dishes held 30 c. c. of the salt solu- 

 tion. Temperatures were taken by means of 

 small thermometers of the clinical type, and 

 readings of the temperature of the solution in 

 the dishes were made several times during the 

 course of the test. It is to be noted that the 

 end-point of the swellings would not have been 

 reached until after 40 to 48 hours in the less- 

 concentrated solutions, but the amount of ex- 

 pansion which might have been displayed in 



the last 12 hours of this period would not have changed the totals 

 greatly or the proportions in any important manner. The data given 

 in table 20 represent the average expansion of sets of 3 sections at 

 16 to 17 C. 



TABLE 20. Swelling of a 

 mixture of agar 90 parts 

 and oat protein 10 parts 

 in distilled water and 

 potassium nitrate at 16 

 to 17 C. 



