782 
Journal of Agricultural Research 
Vol. XXIV, No. 9 
he did not prove that manganese was also necessary when iron was 
available. 
In 1883 Yoshida {12) isolated from the sap of the lac tree a product 
possessing peculiar enzymic properties which he was unable to explain. 
In 1894 Bertrand (z) undertook further work on the nature and 
composition of the product which had been isolated from the sap of the 
lac tree, and found that it contained considerable manganese, which 
gave to the product its peculiar enzymic properties. After several 
years of research on the relation of manganese to the growth of plants 
he concluded that this element is necessary for the normal growth of 
both autotrophic and heterotrophic plants and that its functions can 
not be performed by any other element. 
In 1914 Brenchley (2) published the results of an investigation con¬ 
cerning the effect of manganese sulphate on the growth of barley seedlings. 
She found that with a concentration of 1/100,000 of MnS04 and less a de¬ 
cided stimulation in the growth was produced; with greater concentra¬ 
tions than this, however, toxic effect resulted. In her conclusion with 
respect to the function of manganese in plants she suggests the proba¬ 
bility that manganese may prove to be an essential element in the 
economy of plant life, even though the quantity usually found in plants 
is very small. 
Kelly (5) made a study of the effect produced on different species of 
plants when grown in a natural soil containing a large amount of manga¬ 
nese as compared with the effect produced on the same species when» 
grown on a soil containing only a normal amount of manganese. From 
his results he concluded that the small amount of manganese occurring 
in soils probably performs a twofold function in plant growth: (i) It acts 
catalytically, increasing the oxidations in the soil and accelerating the 
auto-oxidations in plants; and (2) it tends to modify the absorption of 
calcium and magnesium, perhaps by partially replacing calcium from 
insoluble combinations, but especially through a direct effect by which 
the absorption of calcium is increased and that of magnesium is decreased. 
McHargue { 6 ) grew wheat plants to maturity in solution cultures free 
from and containing manganese and found that in the absence of manga¬ 
nese the plants became etiolated and did not develop in a normal way, 
thus showing that manganese is essential to the normal growth and 
maturation of this plant. 
Previous to 1902 but little attention had been given to the occurrence 
and distribution of manganese in soils. During that year Ewell (j) 
made an interesting observation with respect to the occurrence of soluble 
salts of manganese in a certain small area of soil which failed to produce 
crops in a normal way. The results of his investigation showed that 
the small nonfertile area of soil contained relatively large amounts of 
soluble salts of manganese, while the adjacent fertile soil contained none. 
He assumed that the difference in the fertility of the two soils was due 
to the presence of the soluble compounds of manganese. The publication 
of his conclusions apparently awakened a wide interest regarding the 
r 61 e manganese plays in soils. 
In 1907 the United States Bureau of Soils (zo) inaugurated a series of 
experiments with manganese at the Arlington Experiment Farm. Man¬ 
ganese sulphate was applied at the rate of 50 pounds per acre to an acid 
silty clay loam soil, and crops were grown on the treated and untreated 
soil for six years. The application of manganese to the acid soil resulted 
