152 



M. M. McCooL 



TABLE 19. Experiment with Canada Field Pea. Duration, Thirty Days. Data 



FOR Ten Plants 



Composition of solution 



Green weight 

 of roots 

 (grams) 



Average length 



of tops 

 (centimeters) 



Average length 



of roots 



(centimeters) 



N/800 MgCl2+N/2.000 BaCU 

 N/800 MgCl2+N/4,000 BaCh 

 N/800 MgCl2+N/6,000 BaCU 



N/800 MgCh 



N/2,000 BaCl2 



N/4,000 BaCl2 



Distilled water 



3.0 

 8.0 

 7.0 

 6.0 

 3.0 

 6.0 

 7.0 







8.0 

 7.0 

 3.5 

 Slight 

 3.0 

 6.0 



Potassium and barium 



In order to obtain more extensive data with respect to potassium and 

 barium ions, cultures were made up in which these cations were present 

 alone and other cultures in which they were together in solution. The 

 solvent employed was N/1000 CaCl2. It was previously determined that 

 N/1000 CaCl2 is wholly ineffective in preventing the toxicity of barium 

 at concentrations here employed. Osterhout (1907), discussing results 

 obtained from experiments with wheat, states: " If we place grains of 

 wheat in NaCl (or KCl) .05 M very little growth occurs. The addition 

 of a very small quantity of barium (100 c.c. NaCl+1 c.c. BaCl2 .05 M or 

 100 c.c. KCl .05 M + 1 c.c. BaCl2 .05 M) at once produces a splendid 

 growth." 



Toxic strengths of potassium and lethal concentrations of barium were 

 employed in the experiments. It was found that when these ions are 

 present together in the weak solution of CaCl2 mentioned, mutual antag- 

 onism results. It is to be noted that N/25 KCl is highly injurious to 

 seedlings and N/500 BaC^ prevents growth. Appreciable top growth 

 takes place and the toxicity toward the roots is reduced, in cultures com- 

 posed of N/25 KCl + N/500 BaCb. Similar results are obtained when 

 N/25 KCl is present in solution with either N/1000 or N/2000 BaCb. 

 In no combination is the top development of the plants so extensive as 

 in those grown in the control, N/1000 CaCb. 



