222 BOTANICAL GAZETTE [September 



lamella. Both writers agree that Sclerotinia is more virulent on 

 ripe than on green fruit, because in the ripe fruit the middle lamellae 

 are disintegrated and allow easier penetration. 



Cooley found that the fungus coagulates soluble pectin, even 

 when calcium is presumably absent from the medium, and that it 



does not dissolve precipitated "calcium pectinate" suspended in 

 an agar nutrient medium. As to the question whether any pectic 



material is assimilated by this fungus, Hawkins (6) found no 

 diminution in the pentosan content of peaches which had been 

 rotted by it, and Cooley's observation that it could not grow 

 on "calcium pectinate" would indicate failure to assimilate this 

 pectic material, at least. 



The present status of the question of pectin relations of Sclero- 

 tinia cinerea, therefore, is that it disintegrates the tissues by dis- 

 solving the middle lamella with a secreted pectosinase, and prob- 

 ably also with oxalic acid. What disposition is made of the 

 dissolved pectic material, and what function the pectase serves, 

 have not been suggested. The fungus also coagulates soluble 

 pectin by means of pectase. Pectinase (see later for definition) 

 has not been demonstrated. * 



During the course of some work on Sclerotinia the writer (9) 

 made several interesting observations on the behavior of thi 

 fungus toward the various pectic substances. These are recorded 

 in the following notes. 



Assimilation of pectin 



Before recounting the observations made on the pectic relations 

 of this fungus it might be well to explain the nomenclature that 

 has been adopted in this paper. It is the same as that used by 

 Atkins (2). Pectosinase is the enzyme that dissolves the middle 

 lamella, with the formation of soluble pectin. Pectase coagulates 1 



soluble pectin to a gel in the presence of a calcium (or barium or 

 strontium) salt. Pectinase hydrolyzes soluble pectin, and also 

 the gel formed by pectase, to reducing sugars. Such definite 

 names have not been given to the various pectic products ; hence 

 the particular one in question in any particular case can be told 

 only by the context. 



