36 BULLETIN 52, HAWAII EXPERIMENT STATION. 
an excessive amount of iron, manganese dioxid, by removing some 
of this harmful iron, caused an increase in growth. 
Sodium hydroxid titration curves are given for ferric chlorid and 
ferrous sulphate. Determination of the solubilities of iron at different 
hydrogen-ion concentrations show that ferric iron is completely 
precipitated while the solution is still strongly acid, and that ferrous 
iron is soluble under fairly alkaline conditions. 
This difference in solubility of ferric and ferrous iron affords an 
explanation of the manner in which manganese induces chlorosis. 
Manganese dioxid, either present as such or formed from manganous 
salts, would keep the iron present oxidized to the much more diffi- 
cultly available ferric form. 
A description is given of field experiments in which solutions of 
iron salts were applied to the leaves of pineapple plants on the manga- 
niferous Hawaiian soils. This treatment effected immediate cure 
of the " toxic effects" of manganese and induced a normal growth. 
The treatment was quickly adopted by all the pineapple growers 
having manganiferous soils and is now being regularly used on 
considerably over half of the Hawaiian pineapple fields. 
LITERATURE CITED. 
(1) Aso, K. 
1902. On the physiological influence of manganese compounds on 
plants. Bui. Col. Agr. Tokvo Imp. Univ., Japan, v. 5, no. 2, pp^ 
177-185. 
(2) 1904. On the practical application of manganous chlorid in rice culture. 
Bui. Col. Agr. Tokyo Imp. Univ., Japan, v. 6, no. 2, pp. 131-133. 
(3) 1907. On the continuous application of manganous chlorid in rice 
culture, II. Bui. Col. Agr. Tokvo Imp. Univ., Japan, v. 7, no. 
3, pp. 449-453. 
(4) Bernardini, L. 
1910. Funzione del manganese nella concimazione. Staz. Sper. Agr. 
ItaL, v. 43, no. 3, pp. 217-240. 
(5) Bertrand, G. 
1897. Sur rintervention du manganese dans les oxydations provoquees 
par lalaccase. Compt. Rend. Acad. Sci. [Paris], t. 124, no. 19, 
pp. 1032-1355. 
(6) 1905. Sur l'emploi favorable du manganese comme engrais. Compt. 
Rend. Acad. Sci. [Paris], t, 141, no. 26, pp. 1255-1257. 
(7) Birner, H., and B. Lucantjs. 
1866. Wasserculturversuche mit Kafer. Landw. Vers. Stat., v. 8, pp. 
128-177. 
(8) Brenchley, W. E. (Miss). 
1910. The influence of copper sulphate and manganese sulphate upon 
the growth of barlev. Ann. Bot. [London], v. 24, no. 95, pp. 
571-583. 
(9) Brown, P. E., and G. A. Minges. 
1916. Effects of some manganese salts on ammonification and nitrifica- 
tion. Iowa Agr. Expt. Sta. Research Bui. 35, pp. 1-22; 
(10) Carpenter, C. W. 
1918. Report of the Division of Plant Pathology. Hawaii Agr. Expt.. 
Sta. Rpt., pp. 44-45. 
(11) Clark, W. M., and H. A. Lubs. 
1917. The colorimetric determination of hydrogen-ion concentration 
and its applications in bacteriology. Jour. Bact., v. 2, no. l r 
pp. 109-136. 
(12) Deatrick, E. P. 
1919. The effect of manganese compounds on soils and plants. Cornell 
Agr. Expt.' Sta. Memoir 19, pp. 371-402. 
(13) Funchess, M. J. 
1918. The development of soluble manganese in acid soils as influenced 
by certain nitrogenous fertilizers. Ala. Agr. Expt. Sta. BuL 
201, pp. 37-78. 
