18 
BULLETIN 52, HAWAII EXPERIMENT STATION. 
Experiment IV. — Experiment III was repeated, using a different 
form of iron. The different variables were the same as in Experiment 
III except that ferric chlorid was the source of iron, and the plants 
<s /o 20 40 30 
Fig. 2.— (Results of Experiment IV.) Effect of manganous sulphate and manganese dioxid on the 
growth of rice in nutrient solutions supplied with various amounts of iron from ferric chlorid. 
in series A 4 , B 4 , and C 4 were dipped in a 0.5 per cent solution of ferric 
chlorid instead of ferrous sulphate. 
The weights of the plants on the fortieth day are given in Table 12 
and graphically in Figure 2. 
