314 Wormald. — Further Studies of the ‘ Broivn Rot ’ Fungi. I. 
the growth of the hyphae by rendering the food-stufifs in the leaf 
unavailable. 
Two other series of inoculations similar to those described under 
Experiment 2 were carried out at the same time, using a culture derived 
originally from an ascospore of Sclerotinia cinerea. The early stages of 
infection again appeared, as shown by a brown discoloration round the 
punctures, together with a yellowing and distortion of the leaf in the neigh- 
bourhood of the infected areas, but in no case did infection extend to the 
base of the leaf, the brown parts eventually falling out. 
It is evident from these experiments that the conidia of Sclerotinia 
cinerea are able to infect young Victoria plum leaves through punctures, but 
it has not yet been established that they can produce infection of uninjured 
leaves. In severe outbreaks of ‘Wither-Tip’ the disease i$ usually 
associated with aphis attacks ; on the other hand, in the wilt of the short 
shoots there was no evidence of insect injury. The failure to obtain any 
instances of definite infection through unwounded leaves in these experi- 
ments, when observations in the open suggest that such cases occur in 
natural infections, m^y be understood when it is realized that the pustules of 
Monilia cinerea on mummied fruit and dead^ shoots produce conidia 
throughout the winter and spring, and that the leaves are therefore liable to 
infection, whenever favourable conditions supervene, from the time the buds 
open onwards. 
An experiment carried out in the laboratory favours the idea that 
infection of uninjured leaves is possible. Young leaves, on long plum shoots 
placed with their cut ends in water and kept in a moist atmosphere, were 
readily infected by placing conidia of Monilia cinerea, taken direct from 
a dead shoot, in drops of water on the uninjured leaves. Brown areas 
appeared within two days at the inoculated spots, and on the sixth day after 
inoculation several of the leaves were brown throughout and grey Monilia 
pustules were present on them. This experiment is not conclusive 
evidence, as the shoots were under very abnormal conditions and the purity 
of the fungus was questionable ; it suggests, however, a line for further 
research. 
(b) Inoculation of Plums {fruit). 
On July 2, 1919, four plums were inoculated by making a puncture 
through the skin of each with a sterile needle and inserting conidia taken 
from a culture of the Shoot-Wilt fungus growing on steamed potato. All 
became infected and produced grey Monilia pustules within a few days. 
Control plums, punctured but not inoculated, did not become infected. 
By July 19 three of the infected plums had fallen, but the fourth was 
still on the tree and had communicated the rot to two others in contact with 
it. The dimensions of too conidia taken from this plum were found to 
