350 Journal of Agricultural Research voi. v. No. s 



According to Kelley, the action of manganese, especially if present in 

 the soil in relatively large quantities, 2.34 to 9.74 per cent, produces 

 very radical changes in the nutrition of the plant (5). But such quan- 

 tities of manganese as correspond to these percentages are not often 

 found in soils. 



Brenchley (2, p. 583) sums up her observations on the effects of manga- 

 nese on barley thus : 



Manganese sulfate, though not an actual toxic to barley, retards the growth very 

 considerably if supplied in moderate quantities. Minute traces of the salt have a 

 decided stimulative action both on the root and shoot. * * * When supplied in 

 sufficient concentration manganese is taken up by the plant and deposited in the 

 lower leaves. 



Jest (4, p. 87), in treating of the nonessential ash constituents ab- 

 sorbed from the soil by plants, says of silica: 



Although silica may be quite superfluous from the chemical point of view, it may 

 be of great service to the plant in the biological sense. Our knowledge of these sub- 

 jects, despite the amount of work which has been expended on them, is still very 

 imperfect, and it is possible to defend the assertion that all the ash constituents have 

 definite functions to perform, although these have not as yet been determined in all 

 cases, and although these constituents can not be considered as taking part in meta- 

 bolic changes. * - * The occurrence of manganese may, however, be specially 

 noted, as leading to the consideration of a new series of phenomena. It is not widely 

 distributed in the earth, and yet is found, though only in traces, in very many plants. 



In discussing nutritive and stimulative materials he uses the follow- 

 ing language concerning iron (4, p. 88) : 



This distinction is not readily made out in all cases; iron, for example, is a difficult 

 element to deal with, because it is essential only in the minutest traces, and is possi- 

 bly both a nutrient and a stimulant. 



Iron is definitely recognized as essential for the growth of plants, 

 though the quantities required are exceedingly small. 



The presence of manganese in wheat straw has been mentioned by 

 others, but nowhere have I found its quantity given, and it is not men- 

 tioned in connection with the grain. The statement of M. Bertrand (i) 

 that "manganese has been found in many grains"^ is the only one 

 known to me that may indicate the occurrence of this element in the 

 wheat kernel. 



In examining the mineral constituents of Vv'heat {Triticum spp.) I was 

 struck by the fact that there was uniformly enough manganese present 

 to come down with the calcic oxalate and to impart a decided brown 

 color to the calcic oxid when ignited. A few preliminary determinations 

 revealed the fact that there was as much or more manganese than iron 

 present. At the time this observation was made I had examined 25 

 samples of wheat and had found manganese present in every sample. 

 These samples had been grown on the same soil, though the different 

 plots had not received the same fertilization. The supply of manganese 



I Author's translation. 



