
1913] SCHLEY—GEOTROPIC STIMULATION 485 
Kraus. Table II is given merely to show the probable error in 
titration in the following acidity tests of the stimulated shoots. 
Table III shows results of titration of the geotropically stimu- 
lated shoots at varying intervals of time corresponding to the periods 
of maximum acidity and to the period of equal acidity of the con- 
cave and convex halves. 
TABLE Ul 
Vicia Faba SHOOTS GEOTROPICALLY STIMULATED; TERMINAL 4.5 CM. USED 
NO. CC. PER GRAM FRESH WT. 





Time stim. Concave half Convex half Diff. in acidity 
Peunutes, cs eee 0.942 0.715 0. 237 
Roget eee 0.622 0.469 0.153 
I5 Paihia Re ak ane 0.623 0.683 : 
a os Sey ape eee eee 0.900 1.210 °. 
A ER tee ones 1.07 1.19 0.13 
OUTS oe ee 1.01 1.02 0.01 
Se jes plo ee 0.512 0.515 -03 
ee ee ee 0.884 0. 782 0.102 
BR rites toe te ee 0.671 oO. 0.072 


From the tables it will be noticed that the geotropically stimu- 
lated shoot first increases in acidity in the upper (concave) eae 
the observed maximum being 7 minutes. After the maximum t 
acidity of the concave side rapidly diminishes, passing 4 ac 
of about equal acidity in 15 minutes. The convex side more slowly 
approaches a maximum acidity, reaching it in 30 minutes. _ 
the maximum the two sides gradually become equal in acidity 
until at the time of visible response, about two hours, they ts 
practically equal. This equality in acidity continues through : 
period of curvature till the plant has passed the vertical, ai rs 
concave side again becomes more acid (for these ape mi 8 aa 
curved portion which had passed the vertical plane fe ’ 
fig. 5,A). As the shoot straightens again, the acidity ‘os 
on the concave side. The accompanying graph (fig. 6) gives 
average of several experiments for each time indicated. eo 
Since this method measures the titration value but not a 
ion content of the acid, the results are not directly perge 
with the work of FiscHEer, whose conception, nears nature 
change, involves also changes in the amount of salts and 
