MANGANESE CHLOROSIS OF PINEAPPLE. 7 
investigators, however, that manganese in higher concentrations 
causes a bleaching or yellowing of the leaves and a depression in 
growth. 
In connection directly with the manganese problem in Hawaii, 
Kelley (28, 29, 30, 31, 32), as already mentioned, had made a very 
thorough investigation of the manganese problem. He had estab- 
lished the correlation between yellowing of pineapples and an abnor- 
mal amount of manganese in the soil. The very valuable data 
obtained by him in his extensive series of soil and plant analyses 
should be consulted in conjunction with this publication as his 
investigations are complementary to the writer's. The toxic effects 
of manganese were attributed by Kelley to modification in the 
osmotic absorption of lime and magnesia. 
At the time the writer attacked the manganese problem, the 
injurious effects of manganese on plants were attributed by practi- 
cally all scientific investigators to an indefinite " toxic effect" and to 
11 manganese poisoning." A large amount of literature on lime- 
induced chlorosis has been available for many years, and it has been 
known that plants on highly calcareous soils become ehlorotic, and 
that spraying with solutions of iron sulphate overcame this chlorosis. 
No proof, however, had been presented to show that the indefinite 
"toxic effects" of manganese are in any way similar to lime-induced 
chlorosis, nor that manganese causes a deficiency of iron in the plant 
nor that spraying with solution of iron sulphate will cure " manganese 
poisoning." In Hawaii, pineapple plants were dying on hundreds 
of acres of manganese soil. No remedy having been found for this 
condition, except, possibly, heavy applications of stable manure, 
which was expensive, only temporarily beneficial, and limited in supply, 
many thousands of acres have been abandoned or left uncultivated. 
So little understood was the real nature of the manganese problem 
that experiments were being carried on with coral sand on the 
manganese soils. Had the "toxic effect" of manganese been 
known to be due to a depressed assimilation of iron by the plant, 
calcium carbonate, in the form of coral sand, would not have been 
added to depress the assimilation of iron still further. 
THE MANGANIFEROUS SOILS AND THEIR EFFECT ON PINEAPPLE 
AND OTHER PLANTS. 
COMPOSITION OF THE MANGANIFEROUS SOILS. 
The chief difference in chemical composition noticed by Kelley 
between the black soils where ''pineapple yellows" occurred, and 
the normal soils where the plants were healthy, was in the high 
content of manganese of the former. Kelley (32) gives the composi- 
tion of these soils in the accompanying analyses. 
