354 
Journal of Agricultural Research 
Vol. V. No. 8 
minimum and maximum, in spite of the difficulties of the analysis, is 
only 0.004 P er 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 (1), 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 an 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 ioo° C. for 24 hours, to be 0.0003 per 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 [xi weeks from the beginning of the experiment] it was evident 
that manganese was deposited in the leaves even at so low a concentration as 
1:1,000,000 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 
(1) Manganese seems 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 1 to 3 feet, did 
not affect the amount of manganese in the grain. 
