1920] PHILLIPS— GEOTROPISM 175 



• 



shoot was divided as accurately as possible into upper and lower 

 flanks. A sample was cut from one of the flanks, starting at the 

 tip and going as far as was necessary to obtain exactly 0.200 gm. 

 The other flank was left attached to the plant, and kept in a moist 

 dark place while catalase was determined in the first sample. 

 The second flank was then sampled in the same way as the first, 

 and its catalase content determined. Six plants were used for each 

 period of exposure. The catalase content of the upper flank of 

 three of these was determined first, that of the lower flank of the 

 other three first. The o . 200 gm. sample was ground for 2 minutes 

 in a mortar with sand and a little CaC0 3 . It was then washed into 

 the apparatus with '15 cc. of water. After the apparatus had 

 reached the temperature of the bath, 5 cc. of H 2 2 (dioxygen), 

 neutralized with a little CaC0 3 , was added. Shaking was begun 

 at once, and readings of the volume of oxygen evolved were taken 

 every minute for 10 minutes. The bath was kept at 25 C. and the 

 air temperature did not change significantly during any single set 

 of determinations. 



The results given in table V are the cubic centimeters of oxygen 

 evolved in 10 minutes. The average of the results for each of the 

 periods of exposure is in favor of the upper flank, but only in the 

 case of the 1 hour samples were all the results in this direction. In 

 the other sets the individual results vary so widely that no conclu- 

 sions can be drawn from the averages. 



For chemical analysis samples of about 100 gm. fresh weight 

 were used. These were collected in flasks containing 0.5 gm. 

 CaC0 3 and sufficient alcohol so that the final concentration was 

 approximately 80 per cent. It was during the collection of the 

 last of these samples that it became necessary to drop the work. 

 In order that the material might not be lost, H. A. Jones consented 

 to complete the collection and carry out the analyses. The writer 

 wishes to express his thanks to Dr. Jones for his kindness in making 

 this addition to the data possible. 



The soluble and insoluble portions were separated, and total 

 solids determined in each. Sugars were determined as follows, 

 Aliquots of the extract were evaporated to remove alcohol, taken up 

 with water, and clarified with basic lead acetate. The excess lead 



