484 BOTANICAL GAZETTE [DECEMBER 
indicator was tested on several different plants. The results of the 
experiment are given elsewhere in this paper. 
In the case of Vicia Faba the material was prepared as in the 
test plate method; 10-25 cc. of the solution were placed in a porce- 
lain dish and titrated with a #/10 solution of sodium hydroxide. 
The solution was at first grayish opalescent. It gradually changed 
during titration, assuming a yellowish color. Upon neutraliza- 
tion the solution turned the color of the testa of the ripe Vicia 
Faba seed. Excess of sodium hydroxide does not change the color. 
Upon standing 15~-30 minutes, however, the neutralized -solution 
becomes dark brown. 
The work on acidity included (a) tests on the region of greatest 
acidity in the shoot, (b) tests on the right and left halves and back 
and front halves of the unstimulated shoot, and (c) tests on the 
upper and lower (concave and convex) halves of the geotropi- 
cally stimulated shoots. The following table will give illustrations 
of the data obtained in experiments a and 6. The first table gives 



TABLE I 
Vicia Faba shoots in 0.5 cm. lengths from tip downward 
esl GCN ie eer t. 30-€C. per g. wt. 
a0 0 B00 co 80 ge os ys 1.25 cc . 
a0 Oe es fees ge i aeciee e 
eS CO es eter FS 
TABLE II 6 
Vicia Faba SHOOTS; TERM. 4.5 CM. USED 
Right half Left half Front Back 
9.77 0.71 0.91 ©.92 
0.88 0.88 0.84 0.83 
0.89 0.89 0.98 0.94 
°.70 0.67 Oo. 77 0.78 
Av. 0.80 0.78 0.87 0.87 




results for tests on acidity ino. 5 cm. lengths from the tip downward. 
The second table shows the acidity of the unstimulated shoots cut 
longitudinally into right and left halves arid front and back halves 
(figs. 1 and 2). The results as given in table I show decreased 
acidity from the tip downward, which accords with the work of 
