Wormald. — Further Studies of the ‘ Brown Rot ’ Fungi . /. 3 1 1 
Later the infected twigs were cut off and it was found that in both of 
them the mycelium had invaded the twig from the shoot, since hyphae were 
seen in the cortex. A drop of gum had oozed out to the surface of one 
canker. Plate cultures obtained by placing particles of the cortex (three 
particles taken from each canker) on agar, in the way already described for 
isolating the fungus from naturally infected cankers, gave rise in every case 
to typical cultures of Sclerotinia cinerea. 
In the infected leaf of the first series of inoculations it was seen that the 
browning began at the punctures. In the leaf of the second series infection 
started at the edge of the leaf, and there was some doubt as to whether the 
germ tubes had actually penetrated the uninjured epidermis; the leaf was 
quite young, its edges being still recurved, at the time of inoculation, and it 
is possible that, in the act of placing conidia on the lower epidermis, the 
margin of the leaf may have been slightly injured. This result therefore, 
particularly as it was the only positive one of that series, cannot be taken 
as proof that infection can take place on an uninjured leaf. The experiment, 
however, affords evidence that conidia of Sclerotinia cinerea are able to 
produce infection of plum leaves through small wounds, if not through the 
uninjured surface, and also that the mycelium in an infected leaf may extend 
into the shoot and also into the twig bearing the shoot. 
Experiment 1, being carried out under greenhouse conditions, eliminated 
the action of frost as a possible primary cause of Shoot-Wilt. 
Experiment 2. 
This experiment was carried out on Victoria plum trees in the College 
plantation in the spring of 1921. Short lateral shoots were labelled and 
the twigs bearing them were sprayed with sterile distilled water ; one leaf 
on each shoot was inoculated, a leaf which had attained to about half its full 
size being selected and marked with a loop of cotton tied loosely round the 
petiole. As in the previous experiment, two series of inoculations were 
made, (a) in which the leaves were punctured before inoculation, the 
punctures on each leaf being four in number, about 2 mm. apart, and situated 
midway between the middle of the midrib and the margin on one side, and 
(b) in which the leaves were not punctured. Leaves used as controls and 
for comparison were sprayed, some being punctured, but not inoculated. 
Six leaves in each series were inoculated on May 3. 
In series (b) brown ’spots or patches were observed on five of the 
inoculated leaves on May 8, mostly towards the base of the lamina ; a few 
days later these brown portions had fallen out and no further change 
occurred. It is uncertain whether these were infection spots or not, but 
a comparison with the results obtained in series (a) and the fact that similar 
spots were present on comparatively few un-inoculated leaves suggest that 
they were a result of inoculation ; assuming this to be the case, it would 
