324 
Journal of Agricultural Research 
Vol. XIV, No. 8 
N/62.5 sodium hydroxid. Toward gram-equivalent amounts of sul¬ 
phuric acid these organisms behave differently; it seems that sulphuric 
acid is approximately 10 times as toxic to the bacteria as sodium hydroxid 
of the same normality. Growth is retarded in concentrations of Nji.oooy 
and the cells are killed in solutions of the concentration of Nj500 sulphuric 
acid. These results do not agree with those of Beijerinck, who found a 
reaction of Nj 166.6 acid gave optimum growth for Rhizobium legumino- 
sarum. However, this difference in behavior of the bacteria no doubt 
is due to the difference in culture medium. From a glance at the data 
of this table it is plain that R. leguminosarum is much more sensitive to 
sulphuric acid than to gram-equivalent amounts of sodium hydroxid. 
Table II .—Effect of sulphuric acid and sodium hydroxid on the reproduction of alfalfa 
bacteria , strain I 
Normal acid or 
Concentra¬ 
Number of bacteria in x cc. of medium. 
No. 
alkali in ioo cc. 
of medium 
tion of acid 
or alkali. 
Inocu¬ 
lum. 
After 1 
week. 
After 2 
weeks. 
After 3 
weeks. 
After 4 
weeks. 
After 6 
weeks. 
1 
Neutral . 
Neutral. .. 
35,000 
10,650,000 
25,900,000 
55,600.000 
53,200,000 
83,800,000 
2 
0.05 cc. sulphuric 
acid. 
Nj 2,000 .... 
35;000 
9,000,000 
21,520,000 
44,600,000 
32,500,000 
54,900,000 
3 
o-1 cc. sulphuric 
acid. 
Nj 1,000 __ 
35)000 
7,010,000 
19)5^0)000 
44,300,000 
31,000,000 
19,400,000 
4 
o- 2 cc. sulphuric 
acid. 
NI500 . 
35)000 
None. 
None. 
None. 
None. 
None. 
5 
o- 3 cc. sulphuric 
add. 
NI333 . 
35)000 
None. 
None. 
None. 
None. 
None. 
6 
0.1 cc. sodium 
hydroxid. 
N}i,ooo .... 
35)000 
7,000,000 
20,280,000 
42,900,000 
29,200,000 
65 , 500)000 
1 
0.2 cc. sodium 
hydroxid. 
N/soo . 
35)Ooo 
5,070,000 
18,280,000 
31,600,000 
30,100,000 
12,500,000 
8 
0.4 cc. sodium 
hydroxid. 
N}25o . 
35)000 
3,750,000 
13,220,000 
23,600,000 
29,800,000 
28,500,000 
9 
0 8 cc. sodium 
hydroxid. 
N/125 . 
35)Ooo 
7,110,000 
14,540,000 
26,600,000 
21,900,000 
23,600,000 
10 
1.6 cc. sodium 
hydroxid. 
Nf62.s . 
35)000 
None. 
None. 
None. 
None. 
None. 
A comparison of the effect of treatment on the number of bacteria at 
various intervals of time failed to show any decided difference. In rela¬ 
tion to time, the acid or alkali exerted approximately the same effect on 
the multiplication of bacteria after one or six weeks. 
EXPERIMENTS WITH AZOTOBACTER, ALFALFA, LUPINE, RED CLOVER, AND 
SOYBEAN BACTERIA 
The behavior of alfalfa bacteria is in accord with our knowledges of the 
host plant—that is, they are sensitive to acidity. The question which 
naturally suggests itself is that of the relation of other strains of legume 
bacteria to different reactions. In addition to the legume bacteria, one 
strain of Azotobacter was studied. Only one count, two weeks after 
inoculation, was made, since the number of organisms at different inter¬ 
vals of time had failed to show any marked variation. The averages of 
the plate counts after two weeks are given in Table III. The results with 
alfalfa confirm those of the earlier tests and show that this organism is 
