[Vol. 2 



426 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



furnished the writer by Professor Sorauer in 1900 (for a 

 photograph see Duggar, '09, p. 477, fig. 219), and, subsequently, 

 from other points in Germany. It is clearly the "black speck" 

 form of the disease now generally recognized. Professor 

 Kiihn also identified cultures of the American fungus on sugar 

 beets (Duggar, '99) as very close to, if not identical with, his 

 R. Solani. In 1858 Kiihn was obviously unaware of the fact 

 that the violet fungus also occurs on potato in Germany ; and, 

 in fact, he told me in 1900 that it was subsequent to 1858 when 

 he first collected specimens of the violet fungus on this host. 

 "The violet fungus produces no serious epidemics of the 

 potato in Germany," he declared. Professor Kiihn was un- 

 able to locate type material of R. Solani, and such material 

 is doubtless unavailable. Before presenting still other indi- 

 cations pointing unmistakably to their identity, I shall proceed 

 on the basis that it is correct to refer the sterile stages of the 

 commoner American Rhizoctonia on potato and other plants 

 to R. Solani Kiihn, and once studied comparatively there can 

 be no confusion of this plant with R. Crocorum (Pers.) DC. 

 A disease of carrots was also described by Kiihn with which 

 no fungus was positively associated. The indications are in- 

 sufficient to determine whether this was a fungus or a bacterial 

 disease. So far as the writer is aware no disease of carrots 

 in Europe due to R. Solani has since been reported, though 

 in 1900 Professor Kiihn stated as his opinion that carrots as 

 well as beets in Germany were affected by a fungus similar to 

 R. Solani. 



The violet root felt fungus was clearly distinguished by 

 Kiihn ( '58, see pp. 235-237, 243-249) in its occurrence on both 

 beets and carrots. It is not possible to mistake his statements 

 in which the organism on these hosts is referred to Rhizoc- 

 tonia Medicaginis DC." Moreover, he nowhere suggests the 

 combinations R. Baud Kiihn and R. Betae Kiihn, which later 

 crept into the literature of the subject. This fact makes it 

 difficult to understand the nomenclature employed by Eidam 

 ( '87) and Comes ( '91). In discussing a beet disease prevalent 

 in Germany, Eidam refers the organism to Rhizoctonia Betae 

 Kiihn. He gives a description of the disease and of the fun- 



