214 BOTANICAL GAZETTE [MARCH 
duced injurious effects on wheat, while other investigators have 
found stimulation to result from the application of much larger 
amounts. In a number of instances, however, the application of 
different amounts of manganese in field culture has produced no 
apparent effects. 
Regarding the specific effects produced by manganese, 
BERTRAND, as stated above, and a number of other investigators, 
have shown that, on the one hand, the addition of small amounts 
of soluble manganese increases the oxygen-carrying power of the 
oxidases, and on the other, stimulation is produced in the oxi- 
_dizing power of infusions from plants grown under the influence of 
manganese compounds. During recent years an increasing impor- 
tance has been attached to the oxidizing conditions of the soil, and, 
as has been pointed out in the researches of SULLIVAN and REID (7); 
there appears to be a direct correlation between the growth of 
plants (fertility of the soil) and the oxidations going on in the soil. 
The catalytic oxidations in soils have also been found to be pro- 
portional, within certain limits, to the percentage of manganese 
contained therein, and to be susceptible of stimulation by the 
addition of manganese compounds in much the same way 45 
stimulation in the activity of plant oxidases is produced by the 
application of manganese salts. 
Certain other investigators have also studied the effects on the 
solubility of plant nutrient constituents of soils produced by the 
application of manganese compounds. BeRNARDINI (8), [oF 
example, has shown that manganous chlorid causes a mobilization 
of calcium and magnesium from both soils and mineral silicates t 
a greater degree than is produced by potassium, sodium, or ammo 
nium chlorides.! | From these facts the conclusion has been draw? 
that plant stimulation, resulting from the application of nical 
ganese compounds, is probably due to indirect effects on the inert 
bases of soils. As bearing on this phase of the question, ASO (9) 
also pointed out that while a 41.8 per cent increase in the yield of 
rice was obtained from the first application of manganous sulphate, 
similar applications to the same soil the following year produced 
only a 2.2 per cent increase. 
t See Nortin, Ann. Sc. Agron. Ser 4. pp. 1-12. 1913. 
