1914] KELLEY—FUNCTION OF MANGANESE 219 
samples no correlation was found between the percentage of man- 
ganese in the soil or the degree of chlorosis on the one hand, and the 
activity of the oxidizing enzymes on the other. 
These tests have also been made with various other plants, 
some of which show toxic effects from the manganese, and with 
still others that appear not to be affected. On the whole, the 
results again fail to show any relation between the activity of the 
oxidizing enzymes and the percentage of manganese in the soil, 
or the toxic effects. 
As is well known, the activity of oxidizing enzymes in different 
specimens of a given species of plant is by no means uniform when 
grown on normal soils. It has been found, for instance, that 
extracts obtained from the fresh leaves of normal sugar cane and 
pineapples, respectively, varied in their oxygen-carrying power 
between wide extremes. It is also known that pathological dis- 
turbances, caused by attacks of Aphidae, the mosaic disease of 
tobacco, etc., are also associated with accelerated oxidation. The 
autumnal yellowing of plants, incident to maturity, and the devel- 
opment of yellow spots on certain plants, have likewise been shown 
by Woops (15) to be associated with an increased activity of the 
oxidases and peroxidases. 
It seems reasonable to suppose, therefore, that while man- 
§anese has the power of increasing the oxygen-carrying power of 
oxidases, and consequently may, in this way, to some degree bring 
about plant stimulation, the phenomenon of chlorosis cannot be - 
completely explained on the basis of excessive auto-oxidation. 
qT development of chlorosis under the influence of manganese 
'S very probably the result of physiological disturbances of a more 
deep-seated nature. 
Composition or THE AsH.—A number of ash analyses have 
been made for the purpose of determining the effects of manganese 
on the absolute, as well as the relative, absorption of plant food 
elements. The materials for analysis were selected with the 
Sreatest care, so as to secure representative plants of the same 
age and stage of development in a given species. The results are 
Tecorded in table I. 
The data given in table I bring out some interesting facts. In 
