354 Journal of Agricultural Research voi. v. no. s 



minimum and maximum, in spite of the difficulties of the analysis, is 

 only 0.004 P^r cent, calculated on the air-dried wheat. The quantity of 

 manganese found shows about the same maximum variation, but the 

 determinations are mostly quite uniform without regard to the State or 

 country in which the wheat was grown. 



The samples given represent great differences in cultural conditions 

 of both climate and soil, and yet the manganese is always present and 

 in approximately the same quantities; in fact, a greater regularity is 

 found in this respect than for iron in the determinations made. Iron is 

 accepted as an essential constituent of the plant, while the manganese 

 is held to be a nonessential one by most writers. 



Bertrand (i), however, has shown that manganous oxid is essential to 

 the action of laccase; and further, that this enzym is universally present 

 in plants and fulfills a definite function in their metabolism, from which 

 he concludes that manganese is ap essential mineral constituent of most, 

 if not of all, plants. 



The reaction shown when a fresh surface of a potato is treated with a 

 tincture of guaiacum is attributed to the oxidizing action of laccase. If 

 the statements of Bertrand be correct the potato should contain man- 

 ganese. For this reason I determined the manganese in a potato, using 

 a single tuber, and found the amount of manganese in this potato, which 

 had been dried at 100° C. for 24 hours, to be 0.0003 P^r cent, correspond- 

 ing to from 0.00005 to 0.00006 per cent of the fresh tuber. This quantity 

 seems very small, but even much smaller quantities of manganese in 

 nutritive solutions produce decided effects upon vegetation. Brenchley 

 (2, p. 579), in discussing her experiments to determine the effects of 

 manganese upon the growth of barley, says: 



At this date [11 weeks from the beginning of the experiment] it was evident 

 that manganese was deposited in the leaves even at so low a concentration as 

 i: 1,000,000 M. S. and in some cases traces could even be observed in 1:10,000,000 

 M. S. 



The percentages given in my determinations are for elemental man- 

 ganese; Brenchley used manganous sulphate with five molecules of water. 

 She points out that the effects of manganese may be modified by the 

 relative supply of nutrients. 



SUMMARY 



(i) Manganese seem.s to be present in wheat wherever grown, irre- 

 spective of the conditions of soil and climate. 



(2) Manganese is present in the wheat kernel in about the same pro- 

 portion as iron, though iron greatly predominates in soils. 



(3) Fertilizers applied to the soil did not affect the amount of man- 

 ganese stored in the kernels. 



(4) Variation in the quantity of water applied, from i to 3 feet, did 

 not affect the amount of manganese in the grain. 



