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310 Wormald. — Further Studies of the ‘ Brown Rot ’ Fungi. I. 
III. Inoculation Experiments. 
Using pure cultures of the fungus, inoculation experiments were carried 
out as follows : 
(a) Inoculation of plum leaves on short shoots to confirm the evidence 
supplied by observations in the open that the conidia of Sclerotinia cinerea 
are able to cause infection of the leaves and produce cankers on the twigs by 
invasion from the infected leaves. 
( b ) Inoculation of plums (fruit) to ascertain whether the fungus, when 
raised from the small ‘winter conidia’, produces typical ‘summer conidia’ 
when grown on the fruit, as was shown to be the case in the ‘ Wither-Tip’ 
disease. 
(c) Inoculation of apple flowers to determine whether the form causing 
this Shoot-Wilt and canker of plum trees is identical with the form causing 
the ‘ Blossom-Wilt and Canker ’ disease of apple trees (forma mali) or with 
the form commonly occurring on plum and cherry trees (forma pruni ), the 
latter in a considerable number of inoculations having invariably failed to 
induce Blossom-Wilt of apple trees. 
(a) Inoculation Experiment on Plum Leaves. 
Experiment i. 
Young shoots of Victoria plum trees growing in pots in the greenhouse 
were used in this experiment. Two series of inoculations were made on 
April i, 1920, viz. : 
(a) Five of the shoots were sprayed with distilled water ; one leaf on 
each shoot was then punctured (four punctures in a group between the 
midrib and the margin of the leaf) with a sterile needle and the punctured 
parts inoculated with conidia of the fungus. The conidia had been pro- 
duced in cultures on steamed potato, and the inoculation was made by 
taking a particle of the potato on a needle and bringing the conidia-bearing 
surface in contact with the wounded leaf. 
(b) In the second series seven shoots were also sprayed with distilled 
water, and one leaf on each was inoculated with conidia but without the 
preliminary puncturing. 
One leaf only in each series became infected ; notes taken on the 
rate of progress of the disease in these two cases are as follows : 
A pril 1 . 
( a ) One leaf oneach 
of five shoots in- 
oculated at punc- 
tures. 
( \b ) One leaf on each 
of seven shoots 
inoculated with- 
out punctures. 
April 14. 
One leaf only infected ; 
a brown discoloration 
extends to a distance 
of 8 mm. from the 
punctures. 
One leaf only infected ; 
a brown discoloration 
extends from the 
middle of one edge to 
the base of the lamina. 
April 17. 
The whole leaf is flaccid; 
a brown area, about 1 cm. 
wide, extends from near the 
apex of the leaf into the 
petiole ; the rest of the leaf 
is green. 
Petiole and lower parts of 
lamina brown ; apical por- 
tion of leaf still green, but 
flaccicl ; the other leaves on 
the shoot are also wilting. 
April 22. 
Infected leaf with- 
ered ; the other 
leaves of the shoot 
are also wilting. 
A canker has girdled 
the twig; the leaves 
of the terminal 
portion of the twig 
are wilting. 
