6 BULLETIN 52, HAWAII EXPERIMENT STATION. 
(IS) found chlorosis to occur on certain areas of Porto Rican soils 
and attributed it to an excessive amount of carbonate of lime in the 
soil. In this connection Gile notes that — 
Chlorosis (sometimes called icterus, bleaching, or Gelbsucht) is the term 
applied to that condition assumed by the leaves of plants when they fail to 
develop the normal amount of chlorophyll, or green coloring matter, i. e., when 
they are yellowish or white instead of a normal green. Chlorosis, then, does not 
denote a specific disease, but merely a general condition. This condition of 
chlorosis, however, is the result or outward sign of a disease or disturbance in 
the physiology of the plant. To say that a plant is chlorotic or affected with 
chlorosis means merely that its leaves are lacking in chlorophyll; but the chloro- 
sis may have resulted from a bacterial disease, poor drainage, lack of nutriment, 
or some other cause. 
Bleaching was found to occur on soils very high in calcium car- 
bonate while healthy plants were found on a soil containing 1.14 
per cent calcium carbonate and a total lime content of 1.92 per cent. 
Manganese is not associated by Gile with this chlorosis as no man- 
ganese is reported as present in the soils or in the plants. Bleach- 
ing in this case appeared to be somewhat different from the yellowing 
of pineapples which occurs on manganiferous soils. Although a few 
cases of yellowing are noted, the typical appearance described is 
that of "waxy white" or " ivory white." No mention is made of 
the very characteristic red fruit which appears on manganiferous 
soils. The application of stable manure was found to be ineffective 
on these calcareous soils. 
In this, as in previous cases of chlorosis which were induced by 
lack of iron in plants growing on highly calcareous soils, Gile founcl 
that the plants were benefited when the leaves were brushed with 
iron salts in solution, but that the treatment was impracticable for 
Porto Rican conditions. Gile (Id, p. 34) states that — 
It is very doubtful if treatment with iron salts would render pineapple growing 
on calcareous soils commercially successful, as the repeated treatments with 
iron would be expensive and the crop would not be equal to that secured from 
soils naturally adapted to pineapples. 
STATUS OF THE MANGANESE PROBLEM WHEN THE PRESENT 
INVESTIGATIONS WERE UNDERTAKEN. 
From a review of the literature on manganese, it appears that the 
results and conclusions concerning the effect of this element on plants 
are very contradictory. Manganese is commonly thought to exert 
a stimulating action, but there seems to be no positive proof that 
such stimulation is due primarily to manganese. The experiments 
in soil culture are so contradictory that the stimulative effects found 
may be considered due to the effect of the anion, usually the sul- 
phate, which is known to cause decided stimulation, particularly on 
alkaline soils. The possibility of manganese being a necessary ele- 
ment is sometimes discussed because of its occurrence in the ash of 
plants. Aluminum also is found in the ash of plants, but aluminum 
is not considered a necessary component; in fact, under some condi- 
tions there is ground for suspicion that aluminum salts are toxic. 
Results obtained from most of the experiments in nutrient solutions, 
intended to illustrate the stimulating effect of manganese, are of 
very doubtful value since increase in height of a plant during a short 
period of growth is usually the only measurement used to determine 
stimulation. The conclusion seems to be fairly general among most 
