215 
Disease of Greengage Trees. 
left on the bark strips), indicating the penetration of the hyphae in a 
radial direction. In one culture in which the block of wood was 
split down the centre so as to contain some of the pith, the mycelium 
extended both ways on the pith more rapidly than upon the wood. 
In all these cultures after three weeks’ growth pycnidia were 
produced, some of which were of the normal type, others, however 
resembled the apothecia in appearance and were flattened structures 
in various stages of development. The youngest consisted of a boss 
of pseudo-parenchymatous tissue surrounded by a felt-like mass of 
yellowish-green hyphae from the ends of which the conidia were 
abstricted. The majority of the conidia were about half the size of 
those formed in nature and not so markedly crescent shaped ; a fair 
number, however, exactly resembled the normal conidia (Fig. 3, A, J). 
VII.— Inoculation Experiments. 
During the cultural work several inoculations were made on 
young greengage trees in the University Botanic Gardens. Inocu¬ 
lations with pieces of diseased wood and with pure cultures of mycelia 
were carried out in December and January. In each case control 
inoculations were made with (a) sterilised pieces of diseased wood, (b) 
pieces of sterile agar. The inoculations were made at various places 
on both young and old branches. In (a) a hole was cut in the branch 
the same size as the diseased piece of wood which was in the shape 
of a small rectangular block; in ( b ) a T-shaped wound was made 
under the flaps of which the mycelium or agar was inserted. The 
wounds were afterwards covered with tinfoil and bound round with 
wool. 
An inoculation and its control made upon the 21st January, 
1913 was examined upon the 5th March, 1913. No discolouration 
beyond the surface of the wound was observed in the control; but 
in the inoculation with mycelium obtained from acrospores a slight 
discolouration was observed in the immediate neighbourhood of the 
wound. A fair amount of gumming had taken place and hyphae 
similar to those in nature were present in the wood. It seems 
probable, therefore, that Dennatella prunastri is the parasite which 
causes the “die back” of greengages described in this paper. 
Infection of the greengage trees in nature probably takes place 
through wounds on the young shoots. As Dennatella prunastri is 
only found to any extent upon greengages and occurs very 
rarely upon other plum trees it is of economic importance only in 
regard to the former upon which it may work considerable havoc 
in the course of time. As a remedial measure it is suggested that 
