Wormald. — ‘ Brown Rot ’ Diseases of Fruit Trees. II. 157 
The results were the same as those in Expt. 5, except that the extracts 
of normal spurs gave a more distinct yellow colour to the pyrogallic acid 
solution. 
It will be observed that in the earlier experiments of this series 
(Expts. 1-4), which were carried out from May 24 to 28, the extracts of 
normal spurs invariably produced a bright green coloration of the guaiacum 
emulsion, while later experiments (5-7), carried out from May 29 to June 7, 
failed to produce the green coloration of the emulsion and extracts of 
normal spurs gave only a buff yellow. It seemed probable that this yellow 
colour was due to a change occurring in the extract itself which imparted 
a tint to the mixture without any reaction with the emulsion. In this case 
the green colour of the earlier experiments might have been the result of an 
oxidase reaction with the emulsion to produce a blue which, mixed with the 
yellow extract, would give a green. 
That the green colour can be reproduced in this way was shown by 
Expts. 8 and 9. 
Experiment 8. 
A tube was prepared by mixing 
1 c.c. of an extract of an infected spur, 
1 c.c. of an extract of a normal spur, 
5 c.c guaiacum emulsion. 
After incubating for 4 hours at 25 0 C. the contents of the tube were 
a bright green. 
Experiment 9. 
Three tubes were prepared as follows : 
(1) 1 c.c. of extract from infected spur+ 1 c.c. distilled water. 
(2) 1 c.c. extract from infected spur+ 1 c.c. extract of normal spur. 
(3) 1 c.c. extract normal spur+ 1 c.c. distilled water. 
5 c.c. of guaiacum emulsion were added to each and the tubes were 
incubated. At end of 20 hours the contents were 
(1) pale blue; 
(2) bright green ; 
(3) buff yellow. 
In order to ascertain whether the yellow pigment which was produced 
in the extracts of normal spurs could be detected in extracts of infected 
spurs, another experiment was carried out. 
Experiment 10. 
Extracts were made of infected and normal spurs and centrifugalized ; 
each was divided into two portions, one of which was heated for one minute in 
a water-bath at ioo°C. and the other left unheated. The tubes were then 
incubated without the addition of any reagent. 
.. / 
