14 
BULLETIN 52, HAWAII EXPERIMENT STATION. 
With Loew and Sawa's nutrient solution, manganous sulphate did 
not cause chlorosis but a decrease in the dry weights of the plants, 
except in the smallest amount used. On the other hand, manganese 
dioxid and calcium carbonate, singly and in combination, caused a 
tremendous increase in the growth of the plants. Evidently, then, 
this solution contained an excessive amount of iron, and the increase 
in growth was due to manganese dioxid and calcium carbonate 
depressing the assimilation of some of this harmful iron. This nutri- 
ent solution is the one with which Loew and Sawa obtained results 
which they claimed proved the supposedly stimulating effect of 
manganese. The stimulating effect of manganese in this nutrient 
solution is doubtless due to its depressing effect on the assimilation 
of the excessive amounts of iron in the solution. 
With Gile and Carrero's acid nutrient solution, an amount as 
small as 4 milligrams per liter of manganese from manganous sulphate 
(0.001 per cent of manganous sulphate) was sufficient to cause brown 
spotting of the leaves and a decided decrease in rate of growth. 
Practically no growth was made in the presence of manganese 
dioxid or calcium carbonate and the plants were strongly chlorotic. 
The greatly different effects of manganese in these two nutrient 
solutions seemed to be due either to the form or to the amounts of 
iron supplied. A second experiment was therefore undertaken in 
which different forms of iron were used in the same solution. 
Experiment II. — In order to obtain results comparable with those 
recorded by Gile and Carrero (18), it was decided to use their neutral 
nutrient solution in all the later experiments. This solution had the 
composition shown in Table 9. 
Table 9. — Gile and Carrero's neutral nutrient solution. 
Composition. 
Weight. 
Composition. 
Weight. 
Grams. 
10.71 
3.57 
3.57 
21.43 
Sodium sulphate 
Grams. 
3.15 
Monobasic potassium phosphate 
C alcium chlorid 
2.00 
Magnesium chlorid 
2.00 
Distilled water 
100,000 
This experiment was similar to Experiment I. Twelve tests were 
made. 
On the fortieth day the plants were harvested and the weights 
determined. The results are given in Table 10. 
