[Vol. 10, 
428 AMERICAN JOURNAL OF BOTANY 
Table 6. The regions in each experiment on water-absorption where no change in reaction 
took place , or where a change toward greater alkalinity or acidity occurred in the 
buffer mixtures , in consequence of the presence of the potato tissue 
Buffer Mixtures 
Reaction Changed 
toward Greater 
Alkalinity in 
Solutions of pH 
No Change in 
Reaction in 
Solutions 
of pH 
Reaction Changed 
toward Greater 
Acidity in 
Solutions of pH 
0.1 M H3PO4-0.1 M NaOH. 
3-5-54 
5 . 8 - 7.9 
0.01 M H3PO4-0.01 M NaOH. 
4-1-54 
5 - 8 - 8.0 
0.01 M H3PO4-0.01 M NaOH. 
54 
5-6 
5-75-6-6 
0.01 M Na citrate-0.01 M NaOH. 
5-I-5-2 
5-5-S-8 
6 .O- 6.7 
0.002 M Na citrate-0.002 M NaOH. . . 
5-4~5-8 
6.1 
6 . 3 - 6.8 
0.01 M KH phthalate-0.01 M NaOH . . 
4-2-5-5 
5-85-6.3 
6.9-7.6 
Table 7. The original pH values of the buffer mixtures used in the experiments with dyes , 
together with the pH of the solutions after standing in contact with the potato and 
the average; the pH was estimated where starred 
Buffer Mixtures 
of 0.02 M H3PO4- 
0.02 M NaOH 
Buffer Mixtures of 0.002 M H3PO4- 
0.002 M NaOH. 
Buffer Mixtures of 
0.002 M Na Citrate— 
0.002 M NaOH 
Orig¬ 
Final 
Ave. 
Orig¬ 
Final 
Ave. 
Final 
Ave. 
Orig¬ 
Final 
Ave. 
Sol. No. 
inal 
pH 
pH 
inal 
pH, 
pH for 
pH, 
pH, 
inal 
pH, 
pH 
pH 
pH 
3 Hrs. 
3 Hrs. 
5 Hrs. 
5 Hrs. 
pH 
6 Hrs. 
Redist. 
H 2 0 
1 
6-5 
6-3 
6.4 
6.6 
6.4 
6-5 
6.4 
6-5 
6.4 
6-3 
6-35 
2 
2.0* 
2.0* 
2.0* 
2.0* 
3-7 
2.85 
4.1 
3-05 
54 - 
54 
54 
3 
3-1 
3-5 
3-3 
4.2 
5-6 
4-9 
5-7 
4-95 
54 
5-5 
5-45 
4 
4-6 
5 -i 
4-85 
5-6 
5-8 
5-7 
5-9 
5-75 
5-67 
5-67 
5-67 
5 
5 - 6 - 
5-6 
5-6 
5-8 
5-9 
5-85 
5-8 
5-8 
5.8 
5-8 
5-8 
6 
5 - 8 +. 
5-8 + 
5-8 + 
6.1 
6.1 
6.1 
5-8 
5-9 
6.2 
6.2 
6.2 
7 
7.0 
6.9 
6-95 
7.0 
6.8 
6-95 
6.4 
6.7 
6.3 
6.2 
6.25 
8 
8.0 
7.6- 
7-8 
7-7 
7.6 
7-65 
6.8- 
7-25 
6.5- 
6.5 
6 . 5 - 
9 
9.0 
8.05 
8.52 
7.9- 
7-6 
7-75 
6.9 
74 
6.6 
6.4 
6.6 
above 
above 
10 
9-75 + 
8.15 
8-95 
8.1 
7-6 
7-85 
6.8 
7-45 
6.7 
6.6 
6.65 
is obtained with a minimum at pH 6.2-6.25. The curves for the three 
intervals of time are much alike in shape. 
A consideration of the six experiments described permits the following 
statements by way of summary. When discs of potato-tuber tissue approxi¬ 
mately 1 x 15 mm. were soaked in buffer mixtures composed of H3PO4 
and NaOH, secondary sodium citrate and NaOH, or potassium hydrogen 
phthalate and NaOH, the change in weight plotted against the H-ion 
concentration of the solutions expressed as pH produced a curve having a 
double maximum with a minimum between. With the H 3 PQ 4 -NaOH 
series this minimum was located at a pH of 5.8-6.0; with the secondary 
