190 
E. B. MAINS 
Effect of Mineral Salts upon Development 
Two experiments were carried out to discover the effect of mineral 
salts upon the development of Puccinia Sorghi. In the first, water 
cultures were used, while in the second pure quartz sand watered with 
the solutions was employed. 
Experiments 6 and 7. — The solutions used in the first of the two 
were Knop's full mineral nutrient solution, as given by Jost (1907) 
and Miss Wuist (1913), and solutions in which one of each of the eight 
principal elements (Mg, Ca, K, Fe, S, N, P, and CI) were lacking. 
The full nutrient solution consisted of the following in 1,000 cc. of 
distilled water: 
MgS04 25 g. 
Ca(N03)2 i.oog. 
KH2PO4 25 g. 
KCl 12 g. 
FeCls trace. 
The nutrient solution minus calcium was made by substituting 
KNO3 for Ca(N03)2. K2SO4 was substituted for MgS04 to form a 
solution minus Mg. Ca(H2P04)2 and MgCU were substituted for 
KH2PO4 and KCl to form a solution minus K. MgCl2 was substituted 
for MgS04 to form a solution minus S. Ca(H2P04)2 was used in place 
of Ca(N03)2 to give a solution minus N. KNO3 was used in place of 
KH2PO4 to give a solution minus P. KNO3 and FeP04 were used in 
place of KCl and FeCU to give a solution minus CI. And FeCls was 
left out of the full solution to form a solution minus Fe. 
In the second experiment, maize was planted in quartz sand which 
had been thoroughly washed with distilled water and then dried. 
Knop's full mineral nutrient solution of three times the ordinary 
strength was used. The other nutrient solutions were made up a little 
different than in the preceding experiment in that, when an element 
was omitted, the concentration of the other elements in the solution 
was maintained except for the element it was replaced by. Thus for 
example, in — Mg solutions .75 gm. of MgS04 was replaced by 1.04 gm. 
K2SO4 so that there was as much SO4 present as before. The amount 
of the replacing element, K, naturally increases. In the — Ca solution, 
Ca(N03)2 was replaced by Mg(N03)2 and KNO3 so that there would 
not be too great a preponderance of either Mg or K in the solution. 
Kernels of corn were planted in battery jars containing 1.2 kg. of 
