!74 



BOTANICAL GAZETTE 



[FEBRUARY 



could be calculated by interpolation. In only one case was it 

 necessary to extrapolate. 



In table IV are given the P H values of the press juice, and the 

 cubic centimeters of o . 10 N NaOH required to bring 5 cc. of the 

 juice to the neutral point. The results obtained on right and left 

 halves of seedlings not exposed to gravity are given in the last 

 two lines of the table. These results show the magnitude of the 

 differences that might arise from other causes than the action of 

 gravity, such as actual differences between two sides of a plant, 



and errors 



in measurement. 



* 



In a tew 



cases the dineren< 



:es louna 





TABLE IV 









Electrometric determinations on press juice of Vicia 



Faba shoots exposed 





TO GRAVITY 





* 





in 



Hydrogen ion exponent 



Acidity 



in cc. 0.10 N NaOH 



Time of 





per 5 CC. OF JUICE 



EXPOSURE 













Upper flank 



Lower flank 



Difference 



Upper flank 



Lower flank 



Difference 



30 minutes.. . 



6.124 



6.198 



+O.074 



O.81 



1 



O.77 



— O.04 



30 minutes.. . 



6.122 



6.060 



—0.062 



0.89 



1.05 



+O.16 



1 hour 



6.127 



6.207 



+0 . 080 



O.81 



0.71 



— O.IO 





6.137 



6.092 



-O.045 



0.83 



0.92 



+0.09 





6.I44 



6.198 



+O.054 



o.75 



0.77 



+0.02 



2 hours. , . . 



6.132 



6.160 



+0.028 



O.79 



o-7S 



—0.04 



4 hours 



6.203 



6 . 060 



-O.143 



O.74 



0.81 



+0.07 



4 hours 



6.I7O 



6.193 



+O.023 



O. 72 



o.75 



+0.03 



Not exposed . 



6.O79 



6. 102 



+O.023 



O.88 



0.82 



—0.06 



Not exposed . 



6.O48 



6.103 



+0055 



O.87 



0.79 



-0.08 



between the flanks of plants acted on by gravity are greater than 

 those in the blank determinations, but where this is the case the 

 differences are not regular in direction. 



The plan of the work included as complete a study as possible 

 of the various oxidizing enzymes. Only the catalase had been 

 studied when it became necessary to discontinue the work. Deter- 

 minations of catalase activity were made by the method of Apple- 

 man (1), as modified and used by Crocker and Harrington (2). 



Catalase activity decreases from the tip downward, and it is not 

 exactly proportional to the weight of the sample. It was not 

 possible entirely to avoid the errors from both of these sources. 

 The following method was used. After exposure to gravity the 



