154 Wormald . — ‘ Brown Rot ’ Diseases of Fruit Trees. II. 
two parts by pouring 2-5 c.c. into each of two test-tubes. 10 c.c. of the 
guaiacum emulsion were added to each tube. Result : 
From side infected with apple From side infected with plum 
strain. strain. 
From healthy portion. 
Time. 
(1) 
( 2 ) 
(3) 
(4) 
(5) 
(6) 
2 tubes 
2 tubes 
2 tubes 
2 tubes 
2 tubes 
2 tubes 
1 hr. 
bright blue 
bright blue 
pale blue 
very pale blue 
no change 
no change 
2 hrs. 
deep blue 
deep blue 
ditto 
pale blue 
ditto 
ditto 
10 hrs. 
ditto 
a little paler 
nearly decolor- 
ized 
very pale blue 
ditto 
ditto 
20 hrs. 
very pale blue 
very pale blue 
decolorized 
decolorized 
ditto 
ditto r 
Experiment 3. 
This was carried out as in Expt. 2, using another apple similarly 
inoculated. The results were essentially the same as those of Expt. 2 ; the 
control tubes (containing extract of sound tissue) again gave no oxidase 
reaction, the tubes of the apple strain gave a vigorous reaction, and those of 
the plum strain a feeble one (see Fig. 8). 
Experiment 4. 
From the same apple as used in Expt. 2 cubes of tissue were cut from 
infected and healthy portions and extracted, but instead of guaiacum a 2 per 
cent, solution of tannic acid was used as the reagent. Again the reaction was 
greatest in those tubes containing the extract of tissue infected with the 
apple strain, slight in those with the plum strain, and not discernible in the 
control tubes. 
The absence, in these experiments, of any reaction in the tubes con- 
taining the extract of the uninfected portions of the apples calls for remark, 
since Lindet (15) and Thatcher (25) find that apple juice contains an oxidase 
which acts on tannins. It is clear, however, that, in the experiments recorded 
above, if an oxidase were present in the tissues of the apples its action was 
so feeble that it could not be detected by the method adopted, but this in 
no way affects the comparative results, which show that an active oxidase 
was secreted by the apple strain of Monilia cinerea when parasitic within 
the tissues of the apples. 
The conclusion is that the blackening of the apples infected with 
Monilia cinerea forma mali is correlated with the secretion by the fungus of 
an enzyme which oxidizes tannin, and the nigrescence is probably the result 
of the oxidation of tannins in, or immediately below, the skin. 
(c) The Enzyme in Infected Apple Spurs. 
The preceding experiments, which show that the ‘ Blossom Wilt ’ 
Monilia of apple trees produces in liquid culture media and in infected 
apples an enzyme which rapidly oxidizes tannins, suggested that the same 
