W or maid. — 4 Brown Rot ’ Diseases of Fruit Trees. 387 
Monilia fructigenci and M. cinerea on the uninjured skin of the immature 
fruit gave negative results. A similar result was obtained in 1918 when 
conidia of the strain of M. cinerea obtained from a plum (the strain used in 
the experiment just described) were placed on the uninjured skin of 12 
young Monarch plums (not half grown) under conditions favourable for their 
germination, i.e. a gentle rain was falling at the time and the atmosphere 
was saturated with moisture for at least 12 hours after the inoculations 
were made. A few days later 12 Victoria plums were similarly treated, and 
again no infection occurred. Valleau ( 1915 ), working in America with the 
form of Monilia which is found there, obtained different results, for he finds 
‘that infection may take place through the uninjured skin at any time 
during the development of the plum fruit’. 
(e) Plum Flowers inocidated with Strains of Monilia cinerea. 
During the month of April, 1918, a series of three experiments was 
carried out on flowers of plum trees in the open, the number of flowers 
inoculated altogether being 39. 
The strains of Monilia used in each experiment were : 
M. cinerea f. mali, strain from a Brown Rot Canker of an apple tree. 
,, f. pmmi , strain from a mummied plum. 
„ f. pruni , strain from a mummied cherry. 
The inclement weather which prevailed during the latter half of April 
removed many of the inoculated flowers at an early stage in the experi- 
ments, but a sufficient number remained long enough for the following 
conclusions to be drawn. 
All three strains were equally able to cause infection of the flowers. 
Each strain was able not only to kill the inoculated flower but to invade the 
axis of the inflorescence and so cause the death of all the flowers at that 
node. In two of the experiments, in which the conidia were placed on the 
stigmas, the results were similar to those already published ( 1918 ) for 
inoculations carried out in 1917 on plum flowers with a ‘Wither Tip ’ strain 
of Monilia cinerea , except that the progress of the disease, particularly in 
the early stages, was retarded, this being in all probability due to the lower 
temperature. The first symptom of infection after inoculation of the 
stigma is a brown discoloration of the stigma itself, usually within two 
days ; this is followed by an extension of the browning downwards along the 
style, which can be followed day by day until the ovary is reached and soon 
the whole flower is affected. 
In the third experiment the conidia were placed inside the flowers so 
that the disc became inoculated ; in this case the first external evidence of 
infection was the appearance of a brown patch at one side of the calyx tube. 
Since the method adopted in making the inoculations and the results 
