1915] 



DUGOAR RHIZOCTONIA CROCORUM AND R. SOLANI 429 



discussed are ascribed to R. Solani {Corticium vagum B. & C). 



DISTRIBUTION 



Rhizoctonia Solani is distributed throughout the United 

 States and Canada. There is every reason to believe that it 

 exists as a saprophyte in most arable soils, and under certain 

 conditions may attack many species of plants. It is perhaps 

 most frequently noted as a damping off disease in green- 

 houses and seed beds, but this occurrence may be explained 

 by the fact that here the conditions are probably more con- 

 ducive to the pathogenicity of the fungus. On the potato 

 it is likewise wide-spread, although, as noted later, the eco- 

 nomic importance of the diseases induced varies in different 

 sections of the country, probably in accordance with climatic 

 and soil conditions. In all potato-producing states and re- 

 gions it is a well-known disease. On the sugar beet it has been 

 observed in many states. The fact that it is an important 

 disease of one crop or another in every section of the country 

 is alone sufficient indication of its general occurrence. Rhiz- 

 octonia has been mentioned in Brazil by Potel ('00), but it is 

 not clear to which species he refers. 



It is rather surprising to find that R. Solani has received 

 relatively little attention in Europe. Although recognized as 

 inducing a disease of the potato widely distributed in central 

 Europe, and occasionally reported on the beet, yet little care- 

 ful work has been bestowed upon the fungus. Eriksson ( '13), 

 seems to be unfamiliar with the fungus in Sweden. On this 

 account we can gain no incidental information regarding R. 

 Solani as a result of his extensive studies of the related spe- 

 cies in that country. The following will express his attitude 

 regarding R. Solani: 



"II parait tres douteux, du moins si l'on en juge d'apres les 

 descriptions et les figures donnees, que les nouvelles formes de 

 la Rhizoctone sterile signalees dans ces derniers temps par B. M. 

 Duggar et F. C. Stewart sur une quantitc de plantes differentes 

 en Amerique (* * *) soient vraiment identiques aux formes 

 du Rhizoctonia violacea qui ravage l'Europe." 



We have very little data regarding its occurrence in other 

 sections of continental Europe, although from conference 



