424 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
acid end. At the 24-hour weighing the development of bacteria was marked 
and the potato was very flaccid in all cases except in the redistilled water. 
The results of this experiment are given in table 3. In this case the presence 
of the potato shifted the pH toward greater alkalinity in the first two 
solutions, pH 5.1-5.2, and toward greater acidity in the last six, pH 6.0-6.8. 
In solutions 3, 4, and 5, pH 5.5-5.8, no change was noted. 
Fig. 4. Gain or loss in weight of 10 g. of potato-tuber tissue in 6, 12, and 24 hours in 
150-cc. quantities of buffer mixtures of 0.01 M secondary sodium citrate and 0.01 M sodium 
hydroxide. Buffer mixtures replaced at 6, 12, and 24 hours. See table 3. 
When the changes in weight were examined it was found that the in¬ 
crease in weight was considerably less than with the phosphate series of 
buffer mixtures. The potato in all the buffer mixtures showed losses by 
the end of 12 hours which increased in amount by the end of 24 hours. This 
was evidently due to the citrate ion, as the tendency for the increase in 
weight was to become greater or the loss in weight less as we proceed toward 
