Tue Errect oF MANGANESE COMPOUNDS ON SOILS AND PLANTS 379 
2. The majority of experiments indicate that, as Miss Brenchley (1914) 
states, “manganese exerts a toxic influence upon the higher plants, if 
it is presented in high concentration, but, in the absence of great excess 
of the manganese compounds, the poisoning effect is overshadowed by 
a definite stimulation.” 
3. The toxicity of manganese is reduced by nutrient solutions and by soil. 
4. Manganese compounds have been associated with the catalytic 
power of soils and with the oxidizing power of soils and plants. Com- 
paratively large yields have been obtained with manganese fertilization 
under neutral or alkaline soil conditions, and the yields have been cor- 
related with the oxidizing power of the soil. The stimulation of plants 
has in part been explained as due to increased activity in the metabolic 
processes within the leaf. 
5. A stimulation of the ammonification and nitrification in soils has 
also been reported. 
EXPERIMENTAL WORK 
Scope of present study 
In order to test the effect of manganese salts on the growth of plants, 
the weight of wheat seedlings grown in manganese solutions of varying 
concentrations (both in the presence and in the absence of nutrient salts) 
was compared with the weight of plants grown in cultures containing no 
manganese. The concentrations producing stimulation were then used 
as a basis for the applications in the experimental work conducted to 
test the manurial value of manganese when applied to soils. Dunkirk 
silt ‘loam was treated with various manganese salts and planted with 
wheat. An attempt to explain the results obtained led to a study of the 
oxidizing, ammonifying, and nitrifying powers of soils treated with salts 
of manganese. 
Effect of manganese compounds on wheat seedlings grown in water cultures 
Wheat seedlings (Jones’ Paris Prize 106-43) from seeds germinated in 
running tap water were allowed to attain a growth of about eight centi- 
meters, and were. then transferred to culture containers. These were 
salt-mouth bottles of a capacity of 250 cubic centimeters, fitted with 
four-holed corks and wrapped in black paper. Each series was set up 
