350 Journal of Agricultural Research voi. xviii. No. 7- 



SERiES 4 • 



To test the effect of the practically inert material represented by the 

 soil, two pots were started, one in a 4,000 parts per million solution of 

 sodium chlorid and the other in pure carbon black, watered with 4,000 

 parts per million sodium-chlorid solution. The young plants grown in 

 carbon black watered with 4,000 parts per million sodium chlorid were 

 just as poor as those grown in 4,000 parts per million sodium-chlorid 

 solution, indicating that the effect of the soil in overcoming the toxicity 

 of sodium chlorid was due merely to the presence of inert particles. 



SERIES 5 



On March 6 a set of soil bottles was prepared, arranged on a filter 

 rack so that the drainage could be easily collected, and watered with 

 the following solutions: 



SOLUTION NO. CONCENTRATION OF SOLUTION. 



1 Distilled water. 



2 1,000 parts per million of sodium chlorid, 



3 1,500 parts per million of sodium chlorid. 



4 2,000 parts per million of sodium chlorid. 



5 3,000 parts per million of sodium chlorid. 



6 4,000 parts per million of sodium chlorid. 



"When it was found by titration that the drainage was of the same 

 salt content as the original solution, 200 cc. that had passed through the 

 soil and the sand, respectively, were collected from under each pot. 

 These solutions were put into culture bottles and, together with the 

 sand and soil pots, planted with wheat seedlings in the manner before 

 described. We now had plants growing in sand, in the solution that 

 had passed through the sand, in soil, and in the solution that had 

 passed through the soil. The sand and soil pots were watered frequently 

 during the day with their respective solutions until the seedlings were 

 7 days old, when they were photographed (PI. 41). 



The plants grown in the sand pots differed very little from those 

 grown in the solutions that had passed through the sand (PI. 41 , A). The 

 limit of tolerance for each was 3,000 parts per million of sodium chlorid. 

 No difference in the plants growing in the soil could be detected, even in 

 the highest concentration (PI. 41 , B). Although none of the plants grown 

 in the solution which had passed through the soil were quite so good as 

 the control, excellent plants were obtained even in the highest concentra- 

 tion — 4,000 parts per million, which is considerably above the limit of 

 tolerance of sodium chlorid as shown in sand. 



The plants were allowed to grow until March 16, or until they were 10 

 days old. They were then uprooted or removed from the solution and 

 photographed. The plants growing in the sand are shown in Plate 42, A, 

 and those grown in soil in Plate 42, B. The plants grown in the solutions 



