52 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9 
of the Type i solutions recommended by the Committee on the Salt Re- 
quirements of Representative Agricultural Plants. In addition, 2 g. of 
calcium carbonate was added to each jar. Tap water was used instead of 
distilled water. Consequently, the exact composition of this solution is 
not known, but as it gave excellent results, it was probably as good as any 
solution which can be used until we have some definite information con- 
cerning the effect of various solutions on the germination of corn. The 
seedlings were left on the net until the shoots were about 6 cm. long. This 
required from 6 to 9 days. Ten times as many seeds were soaked as were 
finally used. This number was reduced by one half at the time the seedlings 
were transferred to the net. At the time the seedlings were transferred to 
the solutions a second selection of the best seedlings was made. For the 
solution cultures these were wrapped loosely with cotton above the seed 
and placed in one-half-inch holes in paraffined corks. When they were to be 
grown in sand, the seed was placed just below the surface. 
Solution Cultures 
(a) Solution "iJ." The solution which Hartwell and Pember ('18) 
found satisfactory for studying the effect of aluminum sulphate on barley 
and rye, was found to be well adapted for the growth of corn. It was 
modified slightly to secure a better growth of corn. Its composition, as 
used, is as follows : 
CaH4(P04)2 0.00005 M MgS04 0.0008 M 
Ca(N03)2 0015 M Alo(S04)3 000003 ikf 
NH4NO3 001 M MnS04 00001 M 
KCl 0008 M ZnS04 000005 ikf 
Total 0.004168 M 
To this was added 7 mg. of FeP04 per liter. For convenience, this 
solution will be referred to as solution "H." Preliminary experiments 
indicated that Hartwell's solution gave the best results when aluminum, 
zinc, and manganese were added. The work of Maze ('15) on the salt 
requirements of corn suggested this modification. The phosphate con- 
centration of the solution used is about twice that recommended by Hart- 
well and Pember. There was no sign of precipitation when aluminum 
salts were added and the solution was allowed to stand a week. Again, 
all solutions were changed every other day, or at one half the interval used 
by Hartwell and Pember. The ferrous-sulphate solutions were changed 
every day to prevent, as far as convenient, the change from the ferrous to 
the ferric condition. It was impossible to prevent precipitation when the 
ferric salts were used. Consequently, the results may not truly represent 
the relative toxicity of the ferrous and the ferric salts. 
(b) Solution A number of preliminary experiments demonstrated 
that with solutions of Type i as recommended by the Committee on the 
