380 W or maid. — ‘ Brown Rot ’ Diseases of Fruit Trees. 
Since this experiment pointed to a difference in the physiological 
reaction of the two strains to the tissues of the apple in which they were 
growing, the experiment was repeated in 1917 (see Experiment 7) for 
confirmation of the results, using the same two strains, which in the interval 
had been cultivated on sterilized media in the laboratory. The results 
were even more striking than in 1916, showing that the difference was still 
maintained even after cultivation for twelve months, under similar conditions, 
as saprophytes. 
Experiment 7. 
Strains used — as in Experiment 6. 
Two apples were inoculated, as in the previous experiment, on one 
side with the strain from a plum, and on the other with the ‘ Black Apple ’ 
strain ; the inoculations were made on September 14, 1917. 
September 21. 
October 12. 
Result. 
Side inoculated with Plum strain. 
The affected area extended 4-5-5 
cm. from point of inoculation ; it 
was bright brown in colour with 
a rather darker narrow peripheral 
zone. Numerous yellow pustules, 
to 2 mm. diam., were present, grow- 
ing in irregular concentric circles, 
the first at i cm. from the centre. 
The whole of this side was now 
a bright brown and bore numerous 
yellow pustules ; it was much 
shrunken and the skin wrinkled. 
Side inoculated with 1 Black Apple ’ 
strain. 
The rot extended 1-2.3 cm. from 
the point of inoculation ; one apple 
was of a distinctly darker brown on 
this side than on the side infected 
with the plum strain, particularly 
in a zone 1-2 cm. from the centre, 
while on the second apple this 
deeper shade was represented only 
by two blackish spots at 1 cm. from 
the centre. No pustules were pre- 
sent, but conidiophoreshad developed 
along the wound. 
Skin black and but very slightly 
wrinkled ; no pustules present. 
On October 12 the line along which the two strains met was sharply 
marked, and the black colour of the one side, with its almost smooth skin 
and absence of pustules, formed a striking contrast to the other (Fig. 7). 
By October 25 there was no further change except that the 
shrinkage was more pronounced, particularly on the side infected with the 
plum strain. 
Summary of Results of Inoculations on Apples. 
Monilia fructigena and M. drier e a, when growing on apples, can be 
distinguished morphologically, the former producing large (up to 2 or even 
3 mm. in diameter) yellow pustules, the latter smaller grey ones. 
In each species there are two forms which are different physiologically : 
one which, when growing under the conditions which obtained during the 
course of the experiments, develops many pustules, and produces a brown 
