60 AMERICAN JOURNAL OF BOTANY [Vol. 9 
Table 5. The Efect of Acids and Iron and Aluminum Salts upon Growth in Sand Cultures 
PH 
End 2d wk- 
End last wk. 
Sol. "H" 
Nor- 
Weight 
Root 
Transpi- 
Plus 
mality 
of Tops 
Score 
ration 
Ini- 

tial 
50 
500 
1st 
500 
Last 
CC. 
CC. 
50 CC. 
CC. 
SO CC. 
100% 
2 1 
I yjKj /Q 
A Q 
4-9 
6.2 

6.2 
6.4 
6 
6 
fi2 8 prn ) 
(1410 CC.) 
H2SO4 
0.001 
QI 
16 
100 
-2 
0 
54 
3-8 
5-6 
3.8 
3-6 
.002 
jy 
8 
^2 
0^ 
2.8 
34 
3 
34 
3 
3 
HNO3 
.001 
lOI 
14 
98 
1. 
0 
5 
3.8 
6 
4 
3-6 
HCl 
.001 
8q 
I I 
86 
'i 
54 
5.6 
3.6 
3.6 
FeS04 
.0002 
1 02 
9 1 
QO 
99 
46 
5-8 
5-6 
4.8 
4.6 
4.6 
.0004 
88 
2 
7Q 
l6 
5-6 
5-6 
44 
4.2 
4.2 
.0006 
4Q 
49 
60 
3-8 
3-6 
34 
34 
3.6 
Fe.,(S04)3 
.0004 
79 
10 
75 
3.7 
5-8 
5-8 
5-8 
5-2 
5 
Fe(N03)3 
.0004 
80 
8 
69 
3-7 
5-6 
5-8 
5-2 
5 
4.8 
FeCls 
.0004 
66 
6 
61 
3-7 
6 
5-8 
5-6 
5 
4.8 
AL(S04)3 
.0002 
69 
4 
70 
4.1 
6 
6 
6.2 
6 
5-8 
.0004 
66 
3 
69 
3-9 
5.8 
5-8 
5-8 
5-2 
4.8 
.0006 
57 
58 
3-9 
4.1 
4 
A1(N03)3 
.0002 
■73 
6 
74 
4.2 
6 
6 
6.2 
6 
5-8 
.0004 
54 
5 
64 
4.2 
6 
6 
54 
4.8 
4.8 
" 1 
.0006 
54 
58 
4 
4 
5 
AICI3 
.0002 
80 
9 
76 
4.2 
5-8 
6 
6 
5.8 
54 
.0004 
63 
I 
67 
6.2 
6.2 
54 
4.8 
4.8 
" 1 
.0006 
56 
48 
4 
4 
of the peculiar behavior of ferrous sulphate at 0.0002 N and 0.0004 This 
difference is probably accounted for by the better aeration of the sand 
cultures. It is still more unusual to have the lower concentration give a 
slightly higher yield than the control, and 0.0004 N a higher yield than the 
same concentration of the ferric salts. This is probably to be explained by 
the fact that the ferrous solutions were renewed every day; the others every 
3 days. The addition of sand to the culture solution changed greatly the 
toxicity of the acids. The average depression in the sand cultures for 
0.001 N acid was 6 percent, and in the solution cultures for 0.0004 ^ it 
was 21 percent. 
The aluminum salts produced approximately the same depression in 
both types of cultures. The corresponding average depressions in the 
sand and solution cultures for 0.0002 N are 26 percent and 28 percent, and 
for 0.0004 39 percent and 40 percent, respectively. The extensive 
researches of Shive ('20) have indicated that this similarity in effect in 
sand and solution cultures is to be expected w^hen the solutions are changed 
at frequent intervals, and that such factors as chemical action and pre- 
cipitation must not be considered. 
The inhibiting effect upon root development of the acids and of the iron 
and aluminum salts was much less in the sand than in the solution cultures. 
A 0.0006 N concentration of ferrous sulphate in the sand cultures in- 
^ These results are taken from a series run previous to the time the other cultures were 
grown. 
