W 'or maid • — e Brown Rot ’ Diseases of Fruit Trees . II. 153 
(b) 7 A? Enzyme in Infected Apples. 
It has already been shown ( 30 ) that infection of apples with an apple 
strain and with a plum strain of Monilia cinevea gave different results, the 
latter causing a brown rot, while with the former the brown colour gradually 
assumed a darker tone and eventually became black. The enzyme experi- 
ments just described suggested that the differences might be due to the 
oxidase secreted by the apple strain. To verify this the following experi- 
ments were made : 
Experiment i. 
On October 26, 1917, four apples were inoculated, two with an apple 
strain and two with a Wither Tip strain from a plum tree. On Nov. 30 the 
former were black, the latter a bright brown. From each of the four apples 
a cube of tissue (side of cube 5 mm.), including the skin, was cut out at 
i*5 cm. from the point of inoculation and ground up with a few c.c. of distilled 
water in a mortar ; more water was then added to make up to 6 c.c., and 
3 c.c. were poured into each of two test-tubes. 2 c.c. of guaiacum emulsion 
were added to each tube and all were incubated at 30° C. Two control 
tubes were also prepared from a cube of tissue similarly cut from a sound 
apple and extracted. 
The oxidase reaction was greatest in the tubes containing the extract 
of the apple infected with the apple strain ; the other tubes (including the 
controls) also gave the reaction, but the colour change was feebler. 
Experiment 2. 
The strains were those used in Expt. 1. An apple was inoculated on 
Nov. 28 on one side with the apple strain, and on the other with the plum 
strain. By Dec. 1 1 both strains had caused a discoloration of the surface, 
but there was still a strip of healthy tissue midway between the two infected 
areas. Six cubes of tissue (side of cube 5 mm.) were cut out of the 
apple, viz. : 
(1) from the side infected with apple strain, at 1 cm. from the edge of 
the discoloured area ; 
(2) as (1), but at 2 cm. from edge of discoloured area ; 
(3) from the side infected with plum strain, at 1 cm. from the edge of 
the affected area ; 
(4) as (3), but at 2 cm. from edge ; 
( 5 ) 
(*) 
from the healthy portion of the same apple. 
Each cube of tissue was ground in a mortar with a little distilled water, 
and more water was then added to make up to 5 c.c. ; this was divided into 
