216 BOTANICAL GAZETTE [MARCH 
A study of the literature on this subject, embracing as it does 
experiments with a considerable range of plants, reveals discrep- 
ancies, and, in the opinion of the writer, casts doubt on the adequacy 
of either one or both of the above mentioned conceptions as fur- 
nishing sufficient basis for a complete explanation of the function 
of manganese in plants. In this connection, the application of the 
principles of plant physiology, particularly osmosis in its bearing 
on the absorption of chemical substances from soils, naturally 
raises the question of the influence of soluble manganese on 
the selective absorption of the necessary nutrient elements. 
SCHREINER and SKINNER (12) have shown, for example, that small 
amounts of cumarin materially alter the absorption of potash by 
wheat seedlings; that quinone modifies the osmotic absorption of 
phosphoric acid; and that vanillin and dihydroxystearic acid 
exert a noteworthy influence upon the absorption of nitrates. Up 
to the present time the fundamental steps and the specifics of these 
reactions have not been elucidated. The exact “how” as yet can 
only be inferred. With regard to the specific effects on the osmotic 
phenomenon produced by small amounts of inorganic elements 
occurring in soils, other than the so-called plant food elements, 
little indeed is known. It is reasonable to suppose, a priori, 
that some osmotic effect would be produced. In fact, it seems 
improbable that the presence of any considerable amount of an 
electrolyte in the nutrient solution would exert a strictly neutral 
effect. 
For a number of years the writer has studied the effect of man- 
ganese on plants. A preliminary report of this work was publish 
in 1908 (13), in which it was shown that certain soils of Oahu, used 
for pineapples, contain abnormally high percentages of manganese. 
n these areas the pineapple undergoes the phenomenon of chloro- 
sis, the leaves becoming yellow and the fruit pink in color through- 
out the entire period of its growth. The growth of the plant 
stunted and the fruit produced is inferior in size. Further invest 
gation of this question has led to a study of the function of man- 
ganese in plants in general, the results of which, in view of the 
prominence of the question, appear to be of sufficient interest to 
warrant a brief discussion at this time. 
