1923] 



LEHMAN — POD AND STEM BLIGHT OF SOYBEAN 159 



solution. All cultures initially acid became less so, while all 

 initially alkaline became slightly acid. The P H value of the 

 uninoculated controls remained stationary with the exception 

 that those of P H 8.5 and 9.4 shifted to 7.9 and 8.4 respectively. 

 A graphic representation of the correlation between growth and 

 the initial P H values of the culture solution is presented in fig. 11. 

 A consideration of the results of the Experiment I made it 

 seem desirable to follow more closely certain changes which occur 

 in the culture solution during growth. It did not seem that the 

 small amount of growth in the cultures having an initial P H of 

 3.1 and 8.5 as determined at the end of 18 days represented the 

 amount possible, considering that H-ion concentration shifts to 

 a more favorable region during growth and that the same amount 

 of sugar was present initially in all the cultures. Also, it appeared 

 that a knowledge of the changes of both active and total acidity 

 and of utilization of sugar during growth might be of interest. 

 Accordingly, a second experiment was planned involving a larger 

 number of cultures, thus making frequent determinations possible. 

 Experiment II. — Nine series consisting of 4-15 flasks were 

 prepared. All the flasks of a series were started at the same 

 H-ion concentration and a separate series was prepared for each 

 initial P H value selected. All the cultures were inoculated at the 

 same time and examinations were made at intervals of 3-7 days 

 on 2 cultures from each series. Dry weight of mat, amount of 

 sugar, H-ion concentration, and titrable acidity were determined 

 at each examination. Table i embodies the data obtained, and 

 the curves of fig. 12 indicate such relation as may exist between 

 certain factors and processes resident in the cultures involved. 



curves (fig. 12) expressing the relation of time to growth, 

 ing at different H-ion concentrations, are very much alike 

 eries 3-8 inclusive. They rise rapidly to a maximum, or 



The 



for series 3-8 inclusive, 

 thereabout, then flatten, and decline slightly. The curve for 

 series 2 is at first concave and indicates slower growth at the 

 start, but it eventually rises to a height nearly equal that at- 

 tained by the curves for the most favorable solutions. Growth 

 in series 10 was very irregular, some flasks starting much earlier 

 than others. The maximum growth in this series was less than 

 that in any other. In series 1, started at P H 2.5, growth did not 



