AUTOBASIDIOMYCETES 445 



been studied in sufficient detail to be of much assistance. Never- 

 theless, there are certain characters of the mycelium by means of 

 which it was believed to be possible more or less accurately to 

 distinguish the Rhizoctonia from the mycelium of other fungi, or 

 even with some accuracy to distinguish different species of Rhi- 

 zoctonia, or sterile stages referred to the genus. It is only within 

 the past four years that there has been found associated with the 

 sterile mycelial form (the Rhizoctonia) this perfect stage, which 

 has been determined as above given. It would seem probable, 

 however, that we may look upon some of the rather diverse forms 

 of Rhizoctonia as truly sterile stages of the Corticium mentioned. 



Historical. In Europe the genus Rhizoctonia received con- 

 siderable attention by the early mycologists, and various forms 

 were described at some length by the Tulasnes (1851) and by 

 Kiihn (1858). Moreover, all the general texts on plant diseases 

 have given some consideration to these forms. In the United 

 States the Corticium vagum of Berkeley and Curtis was un- 

 known, apparently, prior to 1904 as the cause of plant diseases, 

 yet the fungus had been described as No. 262 of the North 

 American fungi, occurring upon the bark of pine in South 

 Carolina. In 1891 Pammel, in some notes on beet diseases, 

 described a beet root rot, which he believed to be due to Rhi- 

 zoctonia Betce Kiihn. From the mycelial characters of the fun- 

 gus this was unquestionably a Rhizoctonia. Further, in 1892 a 

 sterile fungus as a cause of damping-off in cotton was reported 

 from Alabama (Atkinson), and later the same author described 

 damping-off of various seedlings by a similar unnamed fungus at 

 Ithaca, N.Y. Since 1898 the various plant diseases due to this 

 fungus have received considerable attention in this country. 

 Work at the Cornell and New York (Duggar and Stewart), Ohio 

 (Selby), Colorado (F. M. Rolfs), Florida (F. M. Rolfs), and other 

 experiment stations has demonstrated that the various forms of 

 this fungus are extremely important as the cause of various types 

 of plant diseases in this country. 



Distribution and diversity of forms. The Rhizoctonia is un- 

 questionably widely distributed in the United States and in Europe 

 and Asia. In fact, wherever a careful study of plant diseases has, 

 been made, one or more forms of this fungus have been found^ 



