2 BULLETIN 52, HAWAII EXPERIMENT STATION. 
In many cases the plant ceased growth and began to die back from 
the tips of the leaves. During the earlier stages of development the 
fruit was reddish-pink in color instead of deep green, and in the 
ripened stage the flesh was not only hard and white instead of straw- 
colored, but it also lacked flavor and contained considerable acid. 
Many of the fruits cracked open and decayed before ripening. 
Preliminary reports (24, 25, 26) 2 of the writer's investigations on 
the manganese problem were published in order to make available as 
quickly as possible information concerning the simple remedy dis- 
covered for the " manganese yellows." This remedy, consisting of in- 
expensive sprayings with solutions of iron sulphate, met with 
immediate success and is now being used on thousands of acres of 
Hawaiian pineapples. Considerably over half of Hawaii's production 
of canned pineapples is borne by sprayed plants. This bulletin gives 
a rather detailed account of the results obtained and also of the 
manner in which manganese induces chlorosis. 
REVIEW OF PREVIOUS INVESTIGATIONS ON MANGANESE. 
Manganese is found in small quantities in most soils and in many 
plants. Certain forest trees, notably the conifers, contain rather 
large amounts of manganese. Schroeder (40, 41) reported in 1878 
the occurrence of 35.53 per cent Mn 3 4 in the ash of pine needles 
and of 41.23 per cent in the ash of pine bark. Many experiments 
have been made with manganese in different forms as a fertilizer. 
Kelley (32) and Skinner and Sullivan (43) give extensive reviews of 
these experiments. It is not necessary to refer to these in detail, 
as they were carried on in connection with crop production, and 
the results obtained do not show that manganese is valuable as a 
fertilizer. Some investigators have found a stimulation of growth 
from the application of small quantities of various manganese com- 
pounds, while others have found no effects and even a retardation 
of growth. It appears generally that the application of large amounts 
of manganese produces a toxic effect. 
The chemical similarity of manganese and iron has suggested a 
number of interesting experiments dealing with the physiological 
effects of manganese. Unsuccessful attempts were made by Sachs 
(38) , Birner and Lucanus (7) , and Wagner (45) to substitute manga- 
nese for iron in the production of chlorophyll, and an injurious effect 
was noted when manganous and manganic phosphates were sus- 
pended in culture solutions. 
Since the discovery by Bertrand (5, 6) that manganese occurs in 
the ash of oxidizing enzyms, the physiological effects of manganese 
on plants have been generally attributed to some influence of the 
manganese on these enzyms. 
Loew and Sawa (33) in 1902 observed a yellowing of pea plants, 
barley, and soy beans in water-culture experiments with solutions to 
which small amounts of manganese sulphate had been added. The 
addition of manganese sulphate to the usual iron-containing nutrient 
solution caused an increased growth in which yellowing later took 
place. This yellowing is thought to have been due to the increased 
activity of the oxidizing enzyms. They conclude that " manganese 
exerts in moderate quantity an injurious action on plants, consisting 
2 Reference is made by number (italic) to "Literature cited," p. 36. 
