286 



BULLETIN No. 189 



[June, 



Eriksson 38 has described a new combination, Hypoclinus viola- 

 ceus (Till.) Eriks., which he believes is the perfect stage of Rhizoctonia 

 violacea Tul. However, beyond association on different plants in 

 the same field, he appears to have no further evidence to show that 

 the perfect stage which he found on a number of weeds is connected 

 with R. violacea, found on a number of root crops. 



GENERAL CHARACTERS OF RHIZOCTONIA 







The morphological characters of RJiizoctonia Solani Kuhn. vary 

 with the age of the mycelium. The young hyphas branch at an acute 

 angle from the parent hypha, subsequently lying parallel to it. A 

 constriction is shown at the point of union, and a septum is generally 

 laid down a short distance from this point. The threads are colorless 

 and vacuolate. With age the hyphae lie more at a right angle with the 

 main axis, showing less constriction. They deepen in color into a yel- 

 lowish and then a rather deep brown, becoming more or less granular 

 and empty. (Fig. 2.) - Fusion of hyphae is very common and can be 

 observed in any young culture of the fungus. It occurs either between 

 hyphae of the same parent mycelium or between hyphae from separate 

 colonies (Fig. 2). 



On many hosts a short tufted or bushy growth of the mycelium 

 may occur with some strains. This tufted growth is likewise present 



FIG. 2. (1) YOUNG HYPHAE OF Rhizoctonia Solani; (2) OLD, BROWN, AND EMPTY 



OF Rhizoctonia Solani 



