211 



T. H. HARRISON. 



Pathogenicity of the Organism. 



The following steps were taken to prove that the 

 apothecium discovered was really the Ascigerous stage of 

 a Sclerotinia causing "brown rot" and not a harmless 

 Peziza: — 



1. Tissue plantings of the apothecium were made on 

 Potato Dextrose Agar (200 + 15 + 20). A typical Monilia 

 growth resulted which showed zonation and massive grey- 

 brown tufts of conidia. 



2. Ascospore dilutions and separations were made using 

 the same medium. An abundant growth resulted from 

 which pure cultures were obtained. Single spore isolations 

 were made from these cultures. 



3. A prick inoculation was carried out on loquat using 

 conidia from the pure cultures obtained from the ascospores. 

 In three days a chocolate coloured rot had extended over 

 half of the loquat, and in a week the loquat was completely 

 rotted. At the time of writing, twenty-two days after 

 inoculation, the control loquat still shows no sign of rot 

 but is slightly shrivelled. 



4. Single conidia isolated from the infected loquat were 

 sown on slopes of Potato Dextrose Agar (200 + 15 + 20) and 

 the conidia from the resultant growth used to infect an 

 apple of Smith's Pippin variety, On this apple a brown 

 rot with numerous surface tufts of conidia was produced. 

 The rot quickly involved the whole of the apple. 



Intensive microscopical and cultural studies of this 

 apothecium-producing strain of Sclerotinia are being con- 

 ducted, the results of which will form the subject of a later 

 paper. Already there are definite indications, however, 

 that the organism producing the apothecium is Sclerotinia 

 fructigena, and a distinct biologic form from both the 

 European and American species. 



