DISEASES IN GREENHOUSE 121 



parts above. Plants which have recently 

 died have a water soaked appearance, and 

 later covered by a white weft of fungus 

 mycelium, and by sclerotia which appear 

 irregularly on or within the affected stem. 



Pathogenicity. The pathogenicity of 

 this fungus may be readily established by 

 inoculating healthy seedlings with a pure 

 culture of the fungus. The latter is easily 

 re-isolated and the disease produced at 

 will. Moisture is the main factor in fa- 

 voring infection. 



The Fungus. Sclerotinia libertiana, is 

 a fungus too well known to plant patholo- 

 gists and even to practical growers to re- 

 quire much description. Under green- 

 house conditions, the same fungus causes a 

 serious disease on lettuce, cucumbers, to- 

 matoes, violets, and many other plants. 

 When grown on artificial media, there are 

 no differences observed on the different 



