221 



BOTANICAL GAZETTE [march 



concentrations of 0.1N and 0.01N. Since there was always 

 5 cc. of water in the apparatus, the final concentration of the salt, 

 there was o.i N for 0.5 N solutions and 0.02 and 0.002 N for 

 o . 1 N and o .01 N solutions used. 



Oxidation was measured in centimeters of mercury rise by 

 means of the simplified Bunzell apparatus (8). The shaking ma- 

 chine was run at the rate of 106 complete excursions per minute. All 

 experiments were run for 3 hours, readings being taken every 15 min- 

 utes, and a final reading the following morning. When bark was used, 

 the mixtures in the apparatus contained o . 1 gm. of bark, 1 cc. of 

 salt solution, and 4 cc. of 1 per cent pyrogallol solution or salt 

 and pyrogallol with bark omitted, the second combination serving 

 as a control on the first. Preliminary experiments had shown that 

 during the time in which these experiments were run the auto- 

 oxidation of the pyrogallol was usually not more than the equivalent 

 of 0.15 cm. mercury rise. In the experiment with precipitated 

 oxidase, the precipitate from 2 gm. of bark was dissolved in 20 cc. 

 of water, and 2 cc. of the solution, containing the dissolved precipi- 

 tate obtained from o . 2 gm. of bark, were put in each apparatus, 

 together with the usual amount of pyrogallol and water. All tests 

 were run in duplicate. Two controls were run with each experi- 

 ment, one containing only water, the other bark (or oxidase solu- 

 tion), pyrogallol, and water, but without the addition of salts. 



The figures for P H given in table VII were obtained by means of 

 the apparatus described by Rose (28). 



Discussion 



The chlorides in general retard oxidase activity. The chlorides 

 of potassium, sodium, and lithium depress markedly the oxidation 

 of pyrogallol by bark (table I). Similar results were obtained with 

 all the other chlorides tested, except ferrous chloride (table VI). 

 Ferrous chloride in o . 1 N concentration with bark and pyrogallol 

 showed 1 .79 cm. mercury rise, and with pyrogallol alone 1 .45 cm., 

 compared with the control of pyrogallol and bark as 1 .00 cm. 

 Since ferrous chloride is readily oxidized when exposed to the 

 air, it is quite probable that the oxygen absorption for the most 

 part represents that absorbed in the oxidation of ferrous chloride. 



