1915] 



DUGOAR RHIZOCTONIA CROCORUM AND R. SOLANI 413 



The difficulty in giving an accurate list of hosts compiled 

 from the literature is, however, a serious one, since one can- 

 not be certain that all the observations are carefully made. 

 Again, some mycologists do not distinguish the two species 

 of Rhisoctonia here discussed; thus Salmon ('08), after 

 describing an interesting disease of seakale with all the 

 characteristics of R. Crocorum, goes on to refer to carnation 

 stem rot, damping off, and other diseases as if they were 

 induced by the same fungus, doubtless, however, intended to 

 have reference to another related fungus. 



Eegarding the above-ground symptoms of affected plants, 

 it may be said that they are not striking, and were it not 

 for the characteristic dead area in the field it would not be 

 an easy matter to designate slightly affected plants. Gen- 

 erally, there is in alfalfa evidence of yellowing, sometimes 

 marked chlorosis, while in beets and carrots there is merely a 

 paler appearance of the foliage, followed by wilting. The 

 critical period for affected alfalfa is usually about the time 

 of the second cutting, and at this time considerable wilting 

 may occur without preliminary indications of lack of health. 

 In these main effects the disease is remarkably similar to the 

 Texas root rot of cotton, alfalfa, and other plants. The un- 

 mistakable symptom is the relatively sudden dying of the 

 plant affected. 



The disease is generally though not necessarily fatal. Even 

 a plant so susceptible as the alfalfa may recover from early 

 injuries, usually with the loss of the tap root. Under cer- 

 tain conditions the disease incites the development of ad- 

 ventitious roots, — which may be a factor in recovery. The 

 progress of the disease in the field is radial, and during the 

 first year especially, circular dead areas mark its presence. 

 The spread of the fungus during the season may be from a 

 few feet to several rods. After the first year or two, con- 

 siderable areas irregular in outline may be involved. 



MYCELIUM AND SCLEllOTIA 



It would be difficult to confuse the mycelium of the violet 

 root felt fungus with any other species, for when one is 



