362 
ROBERT AARON STEINBERG 
factor has been already emphasized. In experiment 35 I have attempted 
to dupHcate the conditions with respect to acidity and the presence of 
calcium ion in the treated solution by the addition of ammonium hydroxide 
and Ca(N03)2 to the untreated Pfeffer solution. The amount of Ca(N03)2 
is of course excessive in this solution as compared with the treated nutrient 
solution where the entire amount of CaCOs added amounted to only one 
and one half percent. The use of one percent Ca(N03)2 was due to an 
error in mixing, it being estimated that a liter of solution had been prepared 
whereas in reality it was only a half liter. 
35. The effect of increased acidity of the treated solution together with that of the addition 
of iron and zinc. 
Strain W, 12 
Yield 
Control 
Sporulation 
H3P04/Flask 
Sporulation 
Ph 
Yield 
Ph 
0.012 g. 
4 
Fair 
0.2 cc. 
0.097 g. 
2-3 
Excellent 
O.OII 
4 
Fair 
0.3 
0.125 
2-3 
O.OII 
4 
Fair 
0.4 
0.I2I 
2-3 
Fair 
0.5 
0.041 
2-3 
Sterile 
Fe2(S04)3/Flask 
Fe2(S04)3 
Yield 
Ph 
Sporulation 
I mg. 
0.030 g. 
3-4 
Fair 
5 
0.033 
3-4 
20 
0.326 
2-3 
Excellent 
50 
0.655 
1-2 
Sterile 
100 
0.823 
1-2 
200 
0.864 
1-2 
Mg. Zn/L 
Mg. Zn/L 
Yield 
Ph 
Sporulation 
I 
O.II5 g. 
3-4 
Fair 
10 
0.067 
3-4 
< ( 
50 
0.054 
3-4 
100 
O.IOO 
2-3 
150 
0.051 
3-4 
Practically sterile 
200 
0.055 
3-4 
I Mg. Fe2(S04)3/Flask 
Mg. Zn/L 
Yield 
Ph 
Sporulation 
0.05 
0.288 g. 
2-3 
Excellent 
0.2 
0.562 
1-2 
Good 
0.5 
0.752 
1-2 
Good 
I.O 
0.710 
1-2 
Sterile 
G.I Mg. Zn/L 
Fe2(S04)3/Flask 
Yield 
Ph 
Sporulation 
0.5 mg. 
0.473 g. 
2-3 
Excellent 
1.0 
0.727 
1-2 
Good 
5.0 
0.685 
2-3 
\ 
