W dr maid. — ‘ Brown Rot ’ Diseases of Fruit Trees . II. - 145 
original culture medium and that the liquid from A was distinctly darker 
than that from B. 
Four c.c. of emulsified gum guaiacum were poured into each of two 
test-tubes ; to one tube was added 1 c.c. from culture A and to the other 
1 c.c. from B. At the end of 30 minutes the contents of the first tube were 
a bright blue, while the latter was unchanged, though a very faint bluish tint 
could be detected after 4 hours. Two other tubes similarly prepared shortly 
afterwards gave a similar result. When either liquid was heated in a water- 
bath at ioo° C. for minutes, before adding the emulsion, no trace of the 
blue coloration appeared. 
The mycelium from these cultures was washed with distilled water, 
dried in a thermostat at 30° C., cut up into small pieces, and stored in 
stoppered bottles until required, o-i grm. of the dried mycelium of each 
strain was weighed out, soaked in a few c.c. of water, and pounded in 
a mortar to obtain an extract which was finally made up to 50 c.c. These 
extracts were tested for oxidase in the same manner as employed for the 
culture media. In this case the plum strain gave the reaction for oxidase, 
but not the apple strain. 
The results go in the direction of showing that both strains produce 
the oxidase, but that the apple strain secretes it more readily into the 
culture medium. 
In another experiment, using the same two strains, similar plate 
cultures were prepared, eight in number, viz. : 
A 1, A 2, A 3, A 4, inoculated with the apple strain ; 
Bi, Ba, B3, B4, „ „ plum „ 
Of these Nos. 1 and 2 of each set were incubated at 25 0 C., while Nos. 3 and 
4 were kept at room temperature (about i8°C.). At the end of 9 days 
Nos. 2 and 4 of both sets were tested for the presence of oxidase in the 
liquid, with the following colour changes in the test-tubes at the end of 
1 hour : 
A 2, deep blue ; 
A 4, dark blue ; 
B 2, very faint bluish tint ; 
B 4, no colour change. 
Seven days later the remaining four plates were similarly tested : 
A 1, deep blue ; 
A 3, deep blue ; 
B 1, very faint bluish tint ; 
B 3, no colour change. 
It will be seen that the apple strain gave approximately identical results at 
the end of 9 and of 16 days and whether incubated or kept at room 
temperature ; the liquid in which the plum strain had been growing, however, 
