MANGANESE AND IRON IN GROWTH OF WHEAT 369 



From the data of table 3 it is clear that the injurious effect of 

 the high plane of ferric chloride in Series 1 was correlated with 

 high acidity of the nutrient solutions. It is also clear that while 

 the low plane of sodium bi-carbonate had slight effect toward 

 neutrality the high plane of this salt accomplished the purposed 

 result. Accepting the conclusion of Hartwell and Pember^^ that 

 a considerable range of acidity to alkalinity around the neutral 

 point is favorable for the growth of wheat it would appear that 

 the toxic effect of the high plane of sodium bi-carbonate in 

 Series 2 must be ascribed directly to causes other than the pro- 

 duction of neutrality in the nutrient solution. It seems desir- 

 able, however, to investigate this point in relation to the effects 

 of toxic elements on the basis of the concentration of hydrogen 

 or hj^droxyl ion. 



SUMMARY 



In view of the limited amount of experimental evidence here 

 presented the drawing of broad and final conclusions is unjusti- 

 fied. The following concluding statements seem, however, to 

 be in order: 



1. The effects of manganous and ferric chlorides upon the 

 growth of young wheat plants in water cultures depend partly 

 upon the variety of wheat employed. 



2. The amount of reserve iron in the seed is probably one of 

 the important factors determining the response of wheat plants 

 to supplies of iron and manganese salts. 



3. At the concentration io^ superimposed upon iron-free 

 Knop's solution of 0.2 per cent concentration manganous chlo- 

 ride exerted stronger effects than ferric chloride upon the growth 

 and color of the varieties of wheat employed here. 



4. At the concentration 17^00' superimposed upon iron-free 

 Knop's solution of 0.2 per cent total concentration ferric chlo- 

 ride exerted stronger effects than manganous chloride upon the 

 growth and color of the varieties of wheat employed here. This 



^* Hartwell, B. L. and Pember, F. R., The relation between the effects of 

 liming, and of nutrient solutions containing different amounts of acid, upon the 

 growth of certain cereals. Rhode Island Exp. Sta. Ann. Rept. 20: 358-380, 1907. 



