Apr., 1923] TOTTINGHAM AND RANKIN 
AVAILABILITY OF IRON 
205 
to compare the ferrous with the ferric form of iron, namely, FeS 0 4 and 
Fe 2 (S0 4 )3- 
The culture solution used in this experiment was Livingston and Totting- 
ham’s R 8 Ci. The iron was supplied in three different planes as either 
ferric citrate or Fe 2 (S 0 4 ) 3 , at rates equivalent to 2, 10, and 50 milligrams 
of iron per liter of nutrient solution. A comparison of FeS 0 4 and Fe 2 (S 0 4 ) 3 
was made only at the plane of application of 10 milligrams of iron per liter. 
Six replicative cultures containing five seedlings each were conducted for 
each plane of iron. A pure strain of Marquis wheat furnished by the 
Department of Agronomy of the University of Wisconsin was employed. 
The method of germinating was as follows: The seeds were immersed 
in a solution of 0.1 percent mercuric chloride for fifteen minutes, and 
washed thoroughly with distilled water. They were then soaked in distilled 
water for 5 to 6 hours, after which they were spread upon mosquito netting 
which had been paraffined and stretched over granite-ware pans. The latter 
were 28 cm. in diameter and 10 cm. deep. They were placed in a bath 
supplied with tap water for maintaining a temperature of about 25°C. 
Nutrient solution was supplied continuously from a common reservoir at the 
rate of about 24 liters per pan per 24 hours. The medium employed was 
Livingston and Tottingham’s solution RsCi, diluted to 1/10 its usual 
concentration and adjusted to a pH of 7.5 with M/2 KOH. When the 
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MQM. FbrSo 10 Z 50 10 Z 10 10 
Fe* C IT. Fc"(S0 +) 3 FeSO * FzPO^ 
Fig. 1. Relations between sources of iron, acidity of neutral solution, and growth o 
wheat. 
