Effect of Salts and Acids on Biocolloids and Cell-masses. 47 



The first tests of the effects of incorporated salts were those in 

 which the conditions of the plant were simulated, and the most rational 

 procedure seemed to be one in which the culture salts of plants should 

 be added to a mixture of agar and bean protein, the proportions being 

 as follows : 



TABLE 37. 



gm. 



Agar 9 



Bean protein 1 



Potassium nitrate . 00506 



Di-potassic phosphate . 01622 



Magnesium sulphate . 03660 



Calcium nitrate . . . 03490 



Total 10.09278 



This material was reduced to a dried plate 0.18 mm. in thickness, 

 which was swelled under the auxograph at a temperature of 15 C., 

 giving increases of 1,400 to 1,500 per cent in distilled water, as might 

 be contrasted with 2,100 to about 2,600 per cent in the reactions of 

 similar sections free from salts. 



A second preparation was made, but with ten times the amount of 

 salt used in the first one, the salts forming nearly 9 per cent of the 

 dry weight in one case and 0.85 per cent in the other. The swellings 

 of the biocolloid with the higher salt-content are given below : 



TABLE 38. p. ct. 



Distilled water 958 



Citric acid 361 



Potassium hydroxid 528 



Potassium nitrate, citric acid, 0.01 N 389 



Potassium nitrate, 0.01 M 694 



Potassium hydroxid, potassium nitrate, 0.01 M 472 



The large proportion of salts is seen to hinder swelling in a notable 

 manner. Temperature effects are of great importance in this con- 

 nection, as it was found that sections of the plates which contained the 

 lesser proportion of culture salts and which increased 1,325 per cent 

 in distilled water at 15 C., swelled 2,666 per cent at 48 to 40 C. (See 

 Chapter IX for a fuller discussion of temperature effects.) 



Another set of dried plates was made for the purpose of obtaining 

 comparisons in two directions. The colloidal constituents of the 

 mixture were extended to include agar 70, dextrose 5, gelatine 5, pep- 

 tone 5, asparagine 5, nucleinic acid 5, and bean protein 5 parts, and a 

 set of dried plates was made up as above in distilled water. A second 

 set was made up in the culture solution, in which the salts amounted 

 to 0.85 per cent of the dry weight. The swellings were made on two 

 successive days in a chamber constant at 15 C. It is to be noted that 

 in any inspection of these results rigid comparisons may not be allowed 

 between the swellings of the two kinds of plates in any solution. The 

 basis of all comparisons must be the ratio of the swelling of each plate 

 in any solution to its swelling in distilled water. (See table 39). 



