306 Wormald. — Fiirther Studies of the ‘ Brown Rot ' Fungi. /. 
3 cm. in length, and the wilt, therefore, must have occurred soon after the 
buds expanded (Plate XIII, Fig. i). 
Usually only one wilted shoot was to be found on a twig, but sometimes 
two and occasionally three were found on one twig. They were most 
numerous on trees which had been infected with the c Wither-Tip 5 disease 
during the previous year ; the withered tips had persisted through the 
winter, and during May bore numerous powdery tufts of Monilia cinerea , the 
conidial stage of Sclerotinia cinerea , (Bon.) Schroter. The wilted shoots 
were, as a rule, in close proximity to the dead tips, those shoots immediately 
below such tips being particularly subject to attack. It was suspected, 
therefore, that the wilt was caused by X. cinerea , the withered tips of the 
previous year’s shoots serving, in all probability, as the principal source of 
infection, at any rate in this particular instance, since mummied fruit was 
absent from most of the trees (a result of the almost total failure of the crop 
in 1918), while a few of the trees bore one or two mummies only. The 
weather had been wet and rather cold while the buds were expanding, and 
the damp atmosphere probably favoured infection and also induced free 
development of conidia on the pustules of the withered shoots. 
During the first week of June it was noticed that cankers had developed 
round those nodes where the wilted shoots were inserted. In a few cases 
the canker had girdled the twig and so caused a withering of that portion distal 
to the canker (Plate XIII, Fig. 5). Some of the cankers which had only partly 
girdled the twigs were labelled, so that they could be kept under observation 
to see what rate of progress the cankers made, but from that time onward 
no further increase in the size of the cankers could be detected, and on 
cutting cankers across during the first week of July it was found that 
already callus was developing from the edges of the lesions and tending to 
cut off the dead bark. 
No external signs of a fungus were found on the dead leaves or on the 
cankers at this stage, except in one case where on one shoot pustules of 
Monilia cinerea were found on the petioles. The almost complete absence 
of Monilia pustules from the leaves was undoubtedly due to the dry weather 
which generally prevailed about this time. 1 When, however, infected shoots 
were placed in a moist atmosphere at room temperature (about i8°C.) 
Monilia fructifications appeared on the dead leaves within twenty-four 
hours. 
The cankers were seen as slightly sunken areas, approximately elliptical 
in surface view, being broadest at the node, but, as a rule, they extended 
downwards to a greater distance than upwards. Thus of seventeen cankers 
which were measured two showed an upward extension equal to the down- 
ward, while in the rest the downward extension was the greater. The 
The pustules seen on the petioles were discovered on a day following a showery evening. 
