[Vor. 8 
36 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
gen-ion concentration (Clark and Lubs, 17) was employed, in 
the manner detailed below. 
Experiment 1.—Potato decoction was prepared as usual, then 
neutralized by means of NaOH. The desired reaction was 
obtained by the addition of HCl or NaOH, the procedure being 
then, as in many previous cases, to employ 25 cc. in flask cultures. 
After autoclaving, the actual H-ion concentration was deter- 
mined with the use of a colorimeter as outlined by Duggar and 
Dodge (719), subsequently by Duggar (719). 
The results after 3 weeks’ incubation at 25-28? C. are given 
in the following table. The growth quantities presented in the 
table are invariably an average of 2 cultures. 
TABLE XXIV 
bee EFFECT OF H-ION ae e ene ON THE GROWTH OF THE STRAINS 
N POTATO DECOCTION, THE UPPER SERIES AT ROOM TEMPERATURE 
AND THE LOWER AT 30° C., DRY WEIGHT IN GRAMS 
Strains Pu 2.6 Pa 3.9 Pua 6.0 Pu 7.0 Pu 8.2 Py 8.9 
P1 No 0.128 0.076 0.080 0.074 0.040 
P4 No 0.095 0.084 0.078 0.060 0.035 
P7 No 0.070 0.070 0.060 0.050 0.030 
B1 0.080 0.146 0.084 0.092 0.060 0.020 
H No 0.110 0.083 0.080 0.069 0.040 
B3 No Negl Negl Negl Negl Negl 
Strains Pn 2.8 Pu 3.8 Pg 4.3 Pu 5.7 Py 5.9 Pu 6.7 
P1 0.100 0.088 0.080 0.070 0.060 0.055 
P4 No 0.080 0.054 0.065 0.060 0.051 
P No 0.085 0.060 0.065 0.060 0.055 
B1 0.125 0.095 0.075 0.060 0.068 0.060 
H 0.100 0.090 0.080 0.060 0.070 0.060 
B3 No gr No gr No gr. No gr No gr No gr 
Rather extensive observations were made on the series kept 
at 30? C., as follows: By the second day, the growth of P1, B1, 
and H was evident in the cultures of Px3.8, 4.3, and 5.7, while 
after 5 days the same strains showed growth at P45.9 (natural 
solution) and P46.7. 
