208 



M. M. McCooL 



TABLE 7. Experiment with Canada Field Pea Seedlings. Duration, Ten Days. 



Data for Ten Plants 



Composition of solution 

 (Distilled water as the solvent) 



N/5 SrCl2 



N/7 SrCl2 



N/10 SrCl2. . . . 

 N/500 SrCl2... 

 N/l,000SrCl2. 

 N/2,000 SrCl2. 

 N/5,000 SrCl2. 

 Distilled water 



Increase 





in length 



Increase in length of roots 



of tops 



(centimeters) 



(centimeters) 













0.6 



Slight 



0.6 



Slight 



2.5 



Slight, no lateral roots 



5.0 



1 . 25 No lateral roots 



7.5 



2 . 50 Lateral roots verv short 



7.5 



5 . 00 Lateral roots medium 



7.5 



6 . 25 Lateral roots medium 



Little discussion of the results obtained with full nutrient and soil 

 cultures is required, since the results, with the exception of strontium 

 and barium, are so nearly uniform. The lethal concentrations of the 

 various bases are practically identical, namely, N/3 to N/5. As a 

 rule the seedlings withstand slightly stronger solutions when present in 

 soil cultures. Of course, with longer duration of the experiments many 

 concentrations that have not proved injurious would become so. 



INFLUENCE OF PREVIOUS CONDITIONS OF GROWTH ON THE RESISTANCE TO 

 THE TOXICITY OF VARIOUS IONS 



Pea seedlings were grown for ten days in distilled water, full nutrient 

 solution, and tap water, in order to determine whether age and the 

 composition of the media influenced the resistance of seedlings to various 

 ions. At the end of this period the seedlings were removed, carefully 

 washed with distilled water, and placed in pure solutions of various salts. 

 Final notes were taken three days later. In general it may be said that 

 older seedlings are more resistant than young ones; for example, the roots 

 of young seedlings are killed by N/50 NaCl, whereas the roots of older 

 seedlings withstand much stronger solutions. The composition of the 

 media has little influence on the resistance of the seedlings, as may be 

 seen from the data summarized in Table 8. 



