156 Wormald. — 'Brown Rot ’ Diseases of Fruit Trees . II. 
Experiment 3. 
This was a repetition of Expt. 2, using two other spurs— one infected 
and the other normal. The result was practically the same. 
Experiment 4. 
This was carried out as Expts. 2 and 3, except that the spurs were j 
taken from another variety of apple tree, viz. James Grieve, those used in 
the previous experiment having been taken from a tree of the Lord Derby 
variety ; the method, too, was slightly modified, the extracts being prepared 
as before and then centrifugalized to give a clearer solution. 
The result again was as before. 
Experiment 5. 
Extracts were prepared of two infected and two normal spurs and centri- 
fugalized ; those of one infected and one normal spur were filtered through j 
Swedish filter-paper. The extracts were then tested for their reaction with 
the guaiacum emulsion and with pyrogallic acid. Since the slight turbidity 
of the centrifugalized extracts was not removed by filtering, and as the results 
obtained with filtered and unfiltered extracts of similar spurs were identical, 
the filtering was not repeated in subsequent experiments. 
Tubes of each of the four extracts were prepared, 1 c.c. of the extract 
being placed in each, with 5 c.c. of the reagent, viz. : 
1. Guaiacum emulsion. 
2. „ „ control (i.e. the extract being previously heated). 
3. 2 per cent, pyrogallic acid. 
4 ' !> 3 ) » 
5. „ „ „ control (extract heated). 
Result in unheated tubes : 
Guaiacum emulsion. Pyrogallic acid. 
Time. infected spur. Normal spur. Infected spur. Normal spur. 
4 hrs. bright blue no change no change very pale yellow 
24 hrs. pale blue pale buff yellow deep yellow ditto 
. 
The control tubes of guaiacum emulsion remained unchanged ; a slight 
yellowing of the pyrogallic acid control tubes was the result of the usual 
oxidation of the acid in solution when in contact with the air. 
Expts. 6 and 7 were carried out as in Expt. 5, except that the filtering 
was omitted, and that the infected spurs used were those which had 
been infected by artificial inoculation from pure cultures of apple Blossom 
Wilt strains which are included among those that have been proved to 
produce the enzyme when growing in liquid culture media (Strains 1, 2, 3, 
and 8 of table on page 151). 
