386 Wormald . — ‘ Brown Rot ’ Diseases of Fruit Trees. 
Strains used 
in the inocula- 
tion. 
(Attg. i). 
TREE II. M. cinerea 
f. pruni. 
Strain from 
a mummied 
cherry. 
2 
One-third of 
the surface 
affected ; no 
pustules. 
Whole surface discoloured ; 
shrinkage slight ; pustules 
many. 
Wrinkled and 
shrunken ; nu- 
merous pus- 
tules. 
3 
Nearly half 
the surface 
affected ; a few 
pustules. 
As in 2. 
As in 2. 
4 
Nearly half 
the surface 
affected ; no 
pustules. 
Whole surface discoloured, 
plum shrunken ; pustules 
numerous. 
Fallen. 
5 
One-third of 
the surface 
affected ; no 
pustules. 
As in 4. 
Fallen. 
Aug. 6. 
Aug. 13. 
Aug. 28. 
Half the sur- 
face affected ; 
no pustules. 
Whole surface discoloured 
and wrinkled, plum 
shrunken ; pustules nu- 
merous. One other in 
contact discoloured over 
the whole surface but bear- 
ing no pustules. 
Both plums 
shrunken and 
bearing nu- 
merous pus- 
tules. 
On August 28 some of the plums on these and adjoining trees were 
ripe ; thus those affected from contact with plums artificially inoculated 
must have become infected just as they were ripening, so that the observa- 
tions covered the period from the time the plums were quite small (i. e. 
June 21, when they were not half grown) to their maturescent period. In 
the experiment started on August 1 (results tabulated) there is evidence 
that on plums infected near the time of ripening the apple form of Monilia 
cinerea produces fewer pustules than the Primus form ; the difference, 
however, is not striking and both forms readily cause infection of other 
plums in contact with those primarily infected. The experiments there- 
fore afford no clear explanation of the rare occurrence (perhaps absence) of 
the form mali on naturally infected plums. 
The experiment is interesting as illustrating the rapidity with which 
the rot traverses infected plums. Thus in most cases one-third to one-half 
the surface was discoloured on the fifth day after inoculation, with the 
development of pustules in two instances, while on the twelfth day not only 
were all the primarily inoculated plums affected throughout, but others in 
contact with these were often also discoloured over their whole surface and 
bore pustules. 
It may here be pointed out that experiments carried out at Wye 
suggest that in this country plums are infected by the ‘ Brown Rot ’ fungi 
only through wounds. Inoculations made in 1917 by placing conidia of 
