218 Chlorine and Plant Growth [416 



The investigations here considered in a preliminary way 

 were planned to supplement our knowledge of this subject. 

 They are as yet in early stages of progress, having been begun 

 under the auspices of the Wisconsin Agricultural Experiment 

 Station. It was purposed to measure the responses of various 

 plants, in form and in the weight of plant material produced, 

 to the application of certain chlorides, and to determine any 

 specific results brought about by this application of chlorine, 

 upon the chemical composition of the plants. Greenhouse 

 cultures were grown in nutrient solutions, in pure sand and 

 in Miami silt loam, and field cultures were grown in loam. It 

 may be said of these greehouse cultures, which were partly 

 carried out in the winter, that, while growth is retarded by the 

 decreased light intensities of the winter months, the partial 

 control of climatic and soil conditions in such greenhouse cul- 

 tures assures more reliable comparative results than are usually 

 derived from field plots, with their natural fluctuation of 

 climatic conditions from season to season and of fertility from 

 plot to plot. 



In the water-culture experiments, in the greenhouse, the 

 plants were grown to maturity, in either Tottingham's or 

 Knop's nutrient solution, 1 containing Ca(ISr0 3 ) 2 , KN0 3 , 

 MgS0 4 and KH 2 P0 4 , in proper proportions, with a trace of 

 iron as FeP0 4 . The former had a total osmotic concentration 

 value of about 1.75 atmospheres (0.4 per cent, of salts by 

 weight) and the total osmotic value of the latter was about 

 0.9 atmospheres (0.2 per cent, of salts by weight). In some 

 cases chlorine was introduced by replacing the MgS0 4 of the 

 4-salt solution with a molecularly equivalent quantity of 

 MgCl 2 , in other cases KN0 3 was replaced by KC1, and in 

 still other cases NaCl was superimposed upon the salts usual- 

 ly present. Replacement of MgS0 4 by MgCl 2 resulted in an 

 increased length of roots, for pea, wheat and clover, amount- 



Nottingham, W. E., "A quantitative chemical and physiological 

 study of nutrient solutions for plant cultures." Physiol. Res. I : 

 247-288. 1914. 



