62 BOTANICAL GAZETTE [JULY 
rapid oxidation of pyrogallol than unchanged extract of healthy 
bark. Moreover, when the acidity of healthy bark extract is 
reduced the oxidation is increased, but greatly out of proportion to 
the reduction in acidity. 
TABLE V 
SUMMARY OF EXPERIMENTS WITH EXTRACTS OF HEALTHY AND DISEASED APPLE BARK, 
SHOWING EFFECT OF VARIOUS DEGREES OF ACIDITY OF EXTRACT UPON 
OXIDATION OF PYROGALLOL 
Extract | Extract 
Extract healthy bark, sample 17 age oe gers bark, a — 
Day oF no. 11 | no. 224 
TEsT 
I 2 3 4 s 6 7 i 8 9 
*(3.66), (0.86)| (0.65) | (0.43) | (0.44) | (0.38) | (0.32) | (0.73) | (0-34) 
t 0.83 | 0.37 33 0.29 °.30 0.29 0.28 0.35 0.28 
1st... ..] 0.00.|—- 0.26 [41/24 |~1.92 |—0:.87 |=—0:98 [0.05 |—0. 26° |~-0:57 
Ot 5 0.06 19 ORS oie eis —1.35 |—1.60 |—1.45 |—0.53 |—0.94 
ko re 0.00 |—0.84 |—2.04 |—2.68 |—1.53 |—1.73 |—1.76 |—0.77 |—1.20 
4th —0.05 |—1.01 |—2.34 |—2.92 |—1.63 |—1.89 |—1.85 |—0.86 |—1.36 
5th 0.10! |— 1.25 |~ 2.40 |—3 520 |— 1-58 1-65. | 2-00 OF ie ee 
6th.. OES E048 fe 97 hae ag et ee i bis 4 ehiei os Seaue aes 
7th.. ue, i a Pe —3.59 |—1.89 |—2.13 |—2.19 |.......|..----: 
Sei 36 be eth ed ce PEON bale PAGAL sy Powe SP en pia Dao 
GU ee. Oe teas Ter aie ys at Pte pe ee —1.51 |—1.94 
1 test | Av Aver- 
er- | Aver- | Aver- | Aver- | Aver- | Aver- | Aver- 
ge of 6lage of 3/age of 3 age of 2/age of Olage of 2/age of 2\age of 2 
* The f Shesite tndinet +2 ¢ fa Se 
+ The fig Suuiun tn “its tal line indicat ti f mixture in oxidase apparatus. 
DOTIZONLAr ine 
Further proof of the sensitiveness of the oxidase to changes in 
acidity is found in columns 5 and 6 (table V), where a difference 
of o.o1 cc. of n/2o NaOH gave throughout the experiment a con- 
sistently greater oxidation by the less acid mixture. The figures 
in column 7 seem unreliable and suggest an error in determination 
of the acidity. Column 1 shows the great reduction in oxidation 
produced by increasing the acidity of the mixture in the oxidase 
apparatus to practically that of the unchanged extract. The figures 
in columns 8 and 9 are from an experiment in which extracts of 
healthy and diseased bark were tested at the same time; they show 
again the correlation between acidity and oxidase activity. This 
experiment was continued for #9 days, although during the last 4 
all oxidation, measured by changes in mercury level, had ceased. 
