Aug. 15, 1921 
Effect of Ammonium Sulphate upon Plants 
713 
EXPERIMENT ix. FERROUS SULPHATE AS THE SOURCE OE IRON IN THE 
SOLUTIONS OF SERIES A AND SERIES B 
The solution cultures used in the two series of this experiment were 
the same as those of the preceding experiment except that soluble 
ferrous sulphate was used as the source of iron for the plants instead of 
the insoluble ferric phosphate used in experiment I. As before 0.83 mgm. 
of iron per liter of nutrient solution was supplied to each culture jar at 
the time when the solutions were renewed. The ferrous sulphate was 
added in the form of an aqueous solution which was always freshly 
prepared just before being used. The treatment of the plants before 
and during the growth period, the renewal of the solutions, and the 
general culture methods were carried out in the same manner as were 
those in the preceding experiment. 
: GENERAL APPEARANCE OF THE PLANTS 
During the .first two weeks of the growth period there was no marked 
difference in the general appearance of the plants in the two series. The 
plants in the Tot ting- 
ham series as a whole 
presented perhaps a 
slightly better appear¬ 
ance and showed a 
somewhat sturdier 
growth than did the 
plants in the ammo¬ 
nium - sulphate series. 
After 20 days the plants 
in some of the cultures 
of the ammonium- 
sulphate series showed 
a tendency to become 
weakened; the leaves drooped, presenting angles instead of curves at 
the weakened points, and the growth rates were greatly retarded. 
Later this condition became general throughout the series and increased 
in intensity as the plants grew older, giving them a very dull, unhealthy 
appearance. In a few cultures of this series another symptom of physio¬ 
logical disturbance appeared in the form of narrow white stripes in the 
leaves. This condition was quite unlike: the chlorotic appearance of the 
leaves of plants suffering from lack of iron. 
The plants of the ammonium-sulphate series here presented a sharp 
contrast to those of the Tottingham series in which no toxic symptoms 
occurred at any time during the growth period. The plants in the latter 
series were at all times dark green in color and appeared vigorous and 
healthy, making rapid growth. There were, of course, large differences 
50937°—21 - 2 
T-17335155333113111111 
R-11111113135373315315 
0 - 5 135331111131311357 1 
Fig. 3. —Graphs of actual yield values of wheat roots for the Tottingham 
series and the ammonium-sulphate series of experiment I. 
