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1914] 
COOLEY—SCLEROTINIA CINEREA 303 
method the fungus may be distinctly differentiated from the 
host tissue, the killing and staining agents having little or no 
effect on the host cells. There is a more or less sharply differ- 
entiated line of demarcation between the injured and the sound 
cells, as indicated by the darker color of the former. The effect 
of the fungus is readily discerned by the blackening of the host 
tissue, this being especially noticeable in green plums. Тһе 
discolored and poisoned cells are not at first plasmolyzed, and 
it is to be noted here that discoloration rather than plasmolysis 
should be taken as the index of the toxic action of this fungus 
оп its host. It should perhaps be mentioned here, too, that the 
blackened cells shade off somewhat gradually into the hyaline 
healthy ones, and that, therefore, there is not always a sharp 
line of demareation between the diseased and the healthy cells. 
However, in spite of these difficulties, I was convinced, after 
having examined a large number of sections of diseased and 
healthy tissue, that there is no positive evidence that the host 
cells are discolored, and therefore injured and poisoned, in 
advance of actual penetration by the fungus. 
The indirect method employed to determine the same point 
consisted in applying to sound fruits an extract from decayed 
plums. Fruits were disinfected with mercuric chloride solution, 
washed in sterile distilled water, and inoculated with Sclerotinia 
cinerea. When the plums had become thoroughly decayed 
the juice was extracted and filtered under sterile conditions 
through a Chamberlain filter. The juice thus obtained was 
incubated for one week at a temperature of 22-259 C., and also 
tested on nutrient agar plates, and found to be sterile by both 
methods. From sound plums, which had been disinfected in 
the usual manner, a cone-shaped plug was cut out and the 
resulting cavity filled with this sterile extract,—the controls 
being prepared in a similar manner, using sterile water instead 
of the plum extract. The results were negative, that is, the 
controls were not unlike those treated with the extract from 
decayed plums. 
The same experiment was repeated in a modified form by 
using thin razor sections of both green and ripe plums, the 
sections being made under sterile conditions as before, and ob- 
served in a hanging drop of sterile juice from decayed plums. 
