MANGANESE AND IRON IN GROWTH OF WHEAT 361 



antagonism might vary with the total concentration of the two 

 elements in question. 



EXPERIMENTATION 



Wheat seeds were germinated and the seedlings mounted and 

 grown in the manner'' previously described by one of the writers. 

 Ordinary one pint mason jars were employed exclusively as 

 culture vessels. These were covered with heavy brown wrap- 

 ping paper to exclude light. Knop's solution of a total con- 

 centration of 0.2 per cent, using mono-potassium phosphate but 

 excluding ferric phosphate, was employed as the control nutrient 

 solution. To this were added either manganous or ferric chlo- 



M M 



ride or both, each to the extent of either ^ or con- 



centration in the finished nutrient solution. For the sake of 

 brevity these concentrations will be referred to hereafter as low 

 and high respectively. 



In preparing the stock solutions of these chlorides the assump- 

 tion was made that freshly opened materials corresponded with 

 the formulas MnCL . 4H2O and FeCls . 6H2O. The salts of Knop's 

 solution were dehydrated as described in the work last cited. 

 The distilled water was obtained by condensation into a tin- 

 lined tank from a steam heating system. 



Six plants were grown in each of duplicate portions of nutrient 

 solution and the solutions were renewed every third day. After 

 two weeks of growth in the solutions photographs were *aken, 

 employing an ortho-chromatic filter to give proper value to 

 yellow leaves and thus record chlorotic effects. After three 

 weeks of growth the plants were removed from the supporting 

 stoppers and the roots were washed in running water. The 

 approximate maximum length of roots was then obtained by 

 computing the average length of the two or three longest groups 

 of roots. When but one root was decidedly longer than the rest 

 it was eliminated from the calculation. Tops and roots were 



' Tottingham, William E., A quantitative chemical and physiological study 

 of nutrient solutions for plant cultures. Phj'siological Researches 1 : 133-245, 

 1914. 



