1914] 
COOLEY—SCLEROTINIA CINEREA 323 
skin is punctured. Infection of green fruits is also effected when 
a portion of the mycelial felt of the fungus is laid on the surface 
of the plum. On the other hand, ripe or nearly mature fruits 
may be readily inoculated by sowing a spore suspension on the 
unpunctured surface. 
2. The fungus does not show any particular affinity for the 
middle lamella, but penetrates and permeates with equal avidity 
any part of the host tissue. 
3. A study of the effect of the organism on the host gives no 
positive evidence that a toxic substance is abundantly secreted 
in advance of penetration. 
4. The fungus shows very slight cytolytic action with respect 
to cellulose isolated from the plum, while, on the other hand, the 
organism readily hydrolyzes cellulose from filter paper when 
this is the only carbohydrate supplied. No general cytolytic 
action of the organism on the cell wall of the host is perceptible. 
5. An aqueous solution of pectin isolated from plums was со- 
agulated by Sclerotinia, thus indicating the secretion of the 
enzyme pectinase. In respect to its action on pectic substances, 
Sclerotinia cinerea behaves in a manner similar to that of Pen- 
icillium expansum, yet these two organisms produce very dif- 
ferent effects on the host, the former producing a firm rot and 
the latter a soft one. Neither organism will dissolve calcium 
pectinate. 
6. The experiments on the acid relations of the fungus indi- 
cate that the changing acidity of the host as the fruit reaches 
maturity does not explain the fact that ripe fruit is more sus- 
ceptible to the disease than green fruit. 
7. The brown-rot fungus produces oxalic acid when grown 
either on a fruit juice medium or on peaches. 
The writer takes pleasure in acknowledging his indebtedness 
to Professor B. M. Duggar for his advice and helpful criticism 
in this investigation. Part of this work was done during the 
summer of 1913 in the Laboratory of Plant Pathology of the 
University of Wisconsin, and the writer wishes to express his 
gratitude to Professor L. R. Jones for the courtesy extended to 
him while at Madison. 
Graduate Laboratory, Missouri Botanical Garden. 
