PLATE 136 
A. —Ferric phosphate as the source of iron for plants, 0.75 mgm. of iron per liter of 
nutrient solution. 
The plants in the culture on the left were grown in the Tottingham solution T3R1C5 
modified by substituting ammonium sulphate for the potassium nitrate in equivalent 
osmotic concentrations. The plants are green and healthy. 
The plants in the culture on the right were grown in the Tottingham solution 
T3R1C5 unmodified. The plants are chlorotic and much smaller than those grown 
in the solution containing ammonium sulphate. 
B. ~Ferrous sulphate as the source of iron for plants, 0.75 mgm. of iron per liter 
of nutrient solution. 
The plants in the culture on the left were grown in the Tottingham solution 
T3R1C5 modified by substituting ammonium sulphate for the potassium nitrate in 
equivalent osmotic concentrations. The plants are smalt and unhealthy. 
The plants in the culture on the right were grown in the Tottingham solution 
T3R1C5 unmodified. The plants are large, green, and healthy. 
