1915] 



DUGGAR RHIZOCTONIA CROCORUM AND R. SOLANI 



443 



an important character except under natural conditions. 

 Sclerotia which develop on fleshy organs in moist chambers 

 as well as those which develop in culture show to a certain 

 degree, a semi-persistent hyphal investment ; but such invest- 

 ing hyphae are readily worn away, whereas in the violet 

 fungus they are truly persistent. 



Sections of the denser sclerotia exhibit a fairly homo- 

 geneous structure (fig. 9), with the cells more uniform in size 

 and appearance than in Rhizoctonia Crocorum. 



Fig. 9. Rhizoctonia Solani: a, from a section of sclerotium on potato; b, 

 cells isolated by maceration of sclerotium. 



THE BASIDIOSPORE STAGE, SYNONOMY, AND MATERIAL EXAMINED 



Besides suggestions of a general nature no indications 

 regarding the perfect stage of Rhizoctonia Solani were made 

 prior to the discovery of the Corticium. Prillieux and Dela- 

 croix ('91) described Hypochnus Solani from potato stems, 

 and although at this time the Rhizoctonia diseases were 

 known in Europe no connection with this Hypochnus stage 

 was suspected. The characteristic collar of mycelium was 

 found surrounding the stem just above the surface of the 

 ground, but they found nothing to indicate that the fungus 

 had injured particularly the plant affected. 



Rolfs ('03) found the collar fungus during his studies of 

 potato diseases in Colorado. The material was determined 

 by Prof. E. A. Burt as referable to the species Corticium 

 vagum B. & C. On account of the parasitic habit, however, 



