AUTOBASIDIOMYCETES 



447 



most susceptible are such as lettuce (Fig. 2 1 7), sugar beet, celery, 

 cotton, and the seedlings of various delicate, ornamental plants. 



Upon the potato the fungus has been known for more than 

 half a century in Europe, but largely through the presence of a 

 sclerotial stage upon the tubers. This typical sclerotial stage 



Fig. 219. Rhizoctonia on Potato: European (Upper) and 

 American (Lower) Specimens 



has also been found abundantly in the United States during the 

 past eight years, and it is unquestionably the same as the European 

 form (Fig. 219). In this country, however, the Rhizoctonia was 

 first found upon the stems of dying potato plants, and while it 

 does not seem to be a very serious disease of potatoes, it is one 



