398 



Minnesota Plant Diseases. 



resting spore. Shortly after the mold has become established 

 decay of the mushrooms sets in and the latter may soon be de- 

 stroyed. The trouble can usually be obviated by avoiding too 

 moist conditions. There are several other molds of the bread- 

 mold group which attack picked mushrooms. 



Gall fungus of the wild peanut (Synchytrium decipiens 

 Farl.). This disease has no economical importance in Minnesota, 

 since its host is an unused wild flower, but is of interest on ac- 

 count of the fungus producing it. It is an exceedingly com- 



FIG. 211. Gall fungus on the wild peanut. Minute galls can be seen on the petioles and 



leaflets. Original. 



mon disease and is often found in great abundance. The host 

 plants then appear covered as with a yellow rust, not unlike the 

 cluster-cup stages of a rust fungus. The fungus is a single- 

 celled plant and lives in the cells of the host which it stimulates 

 to an increased growth resembling tiny yellow galls. Swim- 

 ming spores are produced in a manner similar to those of the 

 seedling disease of cabbages. Winter spores are also formed 

 in a similar manner to those of the cabbage disease. The fun- 

 gus is abundant in rainy seasons. 



Fungus gall of wood anemone [Synchytrium anemones 

 (DC.} Wor.]. This fungus is a similar plant to that of the wild 



