4 BULLETIN 52, HAWAII EXPERIMENT STATION. 
Bernardini (4) in 1910 concluded from a series of experiments that 
manganese has a catalytic effect on soils, increasing their oxygen- 
absorbing power and possibly influencing the soil bacteria. Juclging 
from the results of various experiments in which solutions of manga- 
nous chloric! effected replacement of large amounts of lime and mag- 
nesia in certain silicates, he thinks that the stimulating effect of 
applied manganese may be due to some indirect effect of replacement 
rather than to any physiological action. 
Brenchley (8) in water cultures of barley found a stimulating effect 
with very small amounts of manganous sulphate, but noted that the 
plants turned brown and died with large quantities. 
Kelley (28, 29, 30, 31 ) was the first to publish results showing that 
there is a close correlation between the yellowing of pineapples in 
Hawaii and an abnormal amount of manganese in the soil. 
Wilcox and Kelley (Jfi) found, in their study of the effects of man- 
ganese on pineapple plants and the ripening of the fruits, that sec- 
tions showed under the microscope a fading of the chlorophyll and a 
destruction of the organized structure of the chloroplasts. 
In 1912 Kelley (32) published the results of an extensive investiga- 
tion of the effects of these manganiferous soils of Oahu on the pine- 
apple and other plants. Notes were made comparing the appear- 
ance and growth of field plants in manganiferous soil with plants in 
normal soil, and likewise of plants in pots of manganese soil with 
those in pots of normal soil. 
From this investigation Kelley concluded that — 
Various plants when grown on manganiferous soil are affected differently. 
Some species are stunted in growth -and die back from the tips of the leaves, 
which turn yellow or brown and frequently fall off, and a general unhealthy 
appearance results. Other species appear to be unaffected and so far as can be 
judged vegetate normally in the presence of manganese. Microscopic investi- 
gations have shown that in certain instances the protoplasm undergoes changes. 
Occasionally it draws away from the cell walls, the nuclei become brown, and 
plasmolysis takes place. * * * 
From the ash analysis it was found that manganese was absorbed in consider- 
able quantities, and in nearly every instance was greater in the plants from 
manganiferous soil. The ash analysis also shows that a disturbance of the 
mineral balance takes place. The percentage of lime is increased, while the 
absorption of magnesia and phosphoric acid is decreased. * * * 
From these evidences we may believe that the effects of manganese are largely 
indirect and are to be explained on the basis of its bringing about a modification 
in the osmotic absorption of lime and magnesia, and that the toxic effects are 
chiefly brought about through this modification, rather than as a direct effect 
of the manganese itself. 
In 1914 Skinner and Sullivan et al. (43) published results of pot 
and field experiments in which compounds of manganese were 
applied as fertilizers. Changes were observed in the oxidative 
power of the soils as a result of the manganese. Manganese in small 
quantities had a stimulating effect in pot experiments with an unpro- 
ductive soil, but resulted in no increase in growth with a productive 
soil. A five-year field test with an acid soil to which manganous 
sulphate was added at the rate of 50 pounds per acre showed a 
harmful effect on each of the crops grown. In regard to the toxic 
effects of large amounts of manganese, Skinner and Sullivan made 
the following statement : 
Where manganese has been of little value or has given decreased yields, con- 
ditions were such that stimulating actions on plant and microorganisms did not 
come into play, or, on account of the acid reaction of the soil, the effect of the 
