426 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
An examination of the changes in weight showed that much greater 
increases took place with this more dilute solution than were found with 
the stronger one. However, the maximum was past before the 12-hour 
weighing, and by 24 hours the potato in all the buffer mixtures save the 
most alkaline showed a loss in weight. This loss between the 12- and 24- 
Fig. 5. 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 0.002 M secondary sodium citrate and 0.002 M 
sodium hydroxide. Buffer mixtures changed at 6, 12 and 24 hours. 
hour weighings was least in solutions 10, 6, and 5, pH 6.8, 6.1, and 5.8. 
Examining the curve of gain or loss in weight plotted against the pH (fig. 5), 
a minimum was found at 5.7-5.8, at the 6-, 12-, and 24-hour weighings. 
The curves at all three periods are much alike. 
Phthalate—NaOH Series 
The solutions obtained by mixing 0.1 M KH phthalate and 0.1 M NaOH 
as proposed by Sorensen, using the tables given by Clark (3), were diluted 
10 times. The dilution raised the pH of the more acid solutions and lowered 
that of the more alkaline. The potato was weighed at the end of 6, 12, and 
24 hours, and the data are presented in table 4. At the end of 6 hours, 
