224 BOTANICAL GAZETTE [September 



present in the pectin at the start. Very evidently during the 

 growth of the fungus the pectin was assimilated in part, at least. 

 About nine-tenths of the furfural-yielding material of the pectin 

 had disappeared. Presumably this material was utilized by the 

 fungus for energy, but was not stored in any appreciable quantity 

 in the hyphae. It is possible that the small amount found in the 

 latter w r as due to pectic gel enmeshed in the hyphal weft. 



The course of the changes involved when Sclerotinia cinerea 

 grows on a pectin medium may be outlined as follows. There is 

 first a coagulation of the soluble pectin to a gel by means of pec- 

 tase, followed by a slow liquefaction of the gel during the progress 

 of the growth of the fungus. This liquefaction is accompanied by 

 an assimilation of at least the furfural-yielding constituents of the 

 pectin. The fungous hyphae contain very little if any furfural- 

 yielding bodies. It is not known whether the enzyme pectinase 

 is involved in the liquefaction of the calcium pectate. Presumably 

 it must be present in order to liberate soluble split products from 

 the gel before the latter becomes available to the hyphae, although 

 this point has not been demonstrated. 



Hawkins, on comparing the analyses of peaches before and 

 after rotting by Sclerotinia cinerea , found no appreciable change in 

 the pentosan content. This may or may not be evidence contrary 

 to the preceding. In the whole fruit there is an abundance of 

 carbohydrate food other than the pectin, which the fungus can 

 utilize far more readily. As already stated, growth on the pectin 

 medium was very slow, indicating that the fungus can utilize 

 pectin, but with difficulty; hence it is fair to believe that in the 

 presence of abundant sugars in a natural host the pectins are 

 probably not drawn upon for nutrients. 



Secretion of pectase 



Whenever Sclerotinia is grown on a fruit juice medium con- 

 taining soluble pectin, the latter is coagulated to a gel. This gel 

 may vary in extent from a few suspended floes to a solid medium, 

 depending on the amount of pectin present. The gel is insoluble 

 in hot water. It dissolves readily in dilute alkali and in dilute 

 acid, and is reprecipitated from these solutions by alcohol. It is 



