206 



M. M. McCooL 



for magnesium chloric! was fomid to be N/110 (.0093 N), which is much 

 more concentrated than the values obtained by the wTiter for seedlings 

 that remained in the solutions for ten days. 



Toxicity of ammonium 

 Roots of both pea and wheat seedlmgs are especially sensitive to 

 ammonium in distilled water, slight elongation of the roots of either 

 taking place in N/1000 NH4CI. However, much stronger solutions are 

 required in order to prevent top growth; for example, top growth is 

 evident in solutions of N/ 20 NH4CI. 



TABLE 5. Experiments with Pea and Wheat Seedlings. Duration, Ten Days. 



Data for Ten Plants 



Composition of solution 



Pea 



Increase 

 in length 

 of tops 

 (centimeters) ( 



Increase 



in length 



of roots 



^centimeters) 



"^Tieat 



Increase 



in length 



of tops 



(centimeters) 



Increase 



in length 



of roots 



(centimeters) 



Distilled water as the solvent 



N/5 NH4CI 



N/10 NH4CI 



N/20 NH4CI 



N/3ONH4CI 



N/oO XH4CI 



N/lOO XH4CI 



N/500 XH4CI 



N/1,000NH4C1 



Distilled water 



Full nutrient solution as the 

 solvent 



N/3NH4CI 



N/4NH4CI 



N/5NH4CI 



N/IONH4CI 



Nutrient solution 



Soil cultures 



N/3 NH4CI 



N/5 NH4CI 



N/IONH4CI 



Distilled water 











0.5 



1.0 



1.0 



2.0 



3.0 



3.0 



6.0 





 

 

 

 

 Verj^ slight 

 Very slight 

 Very slight 

 7.0 











1.0 



1.5 



3.0 



5.0 



8.0 



8.0 



7.0 



Very 





 

 

 

 

 slight 

 2.0 

 2.5 

 6.5 







SUght 



SHght 



2.5 



7.5 







1.5 

 3.0 

 4.0 







3.0 

 5.5 

 7.0 







2.5 

 4.0 

 7.5 



