152 Journal of Agricultural Research voi. iv, no. 2 



reported a root-rot of beets in Iowa that he beUeved to be due to Rhi- 

 zoctonia hetae Kiihn. The fungus, however, appears to be indistinguish- 

 able from the one which Atkinson and Duggar, respectively, had reported 

 as a damping-off agent on cotton and sugar-beet seedlings and from 

 forms of Rhizoctonia upon a variety of hosts throughout the United 

 States, acting either as damping-off agents or as the causes of other forms 

 of plant diseases. Rolfs (38, 39), working with the fungus on the potato 

 in Colorado, found a fruiting stage which he designated as Corticium 

 vagmn B. and C, var. solani Burt. He was unable to produce the 

 Corticium in culture, but the growth from spores yielded typical Rhizoc- 

 tonia mycelium, and infections on living plants with Rhizoctonia gave 

 rise to Corticium. Shaw observ^ed the fruiting stage on the groundnut 

 and later succeeded in producing it by artificial infection on that host. 

 European workers have referred what appears to be the same basidial 

 form to Hypochnus solani. 



Shaw (42) found marked differences in the character of sclerotia pro- 

 duced by his strains. One which formed small black sclerotia more or 

 less differentiated into cortex and medulla he designated as R. solani 

 Kiihn. The structure of the sclerotia of the other Rhizoctonia which 

 he designated only as Corticium vagum B. and C. appears to correspond 

 closely with that of those obtained in America in cultures and less fre- 

 quently on the host. He believed this Corticium to be identical with 

 the form common on potatoes in America, but was unable to see justi- 

 fication for referring it to R. solani Kiihn. Furthermore, he believed 

 R. violacea Tul. to be a compound species, possibly including R. solani 

 Kiihn and the Corticium, since Prillieux (36, t. 2, p. 144) described 

 R. violacea Tul. as possessing two distinct forms of sclerotia, one of which, 

 according to Shaw, is similar to those of R. solani Kiihn and the other 

 to Corticium vagum. 



A form of crown rot on the sugar beet caused by Rhizoctonia violacea 

 Tul. is well known in certain sections of Europe, but rot from Rhizoctonia 

 solani is unknown there. This fact has led many students to question 

 the identity of the fungus causing the rot of the beet in America. The 

 organism here considered is distinctly different from the Rhizoctonia 

 violacea Tul. type as the writer saw it in Europe on living or preserved 

 material from a variety of hosts, including beets, carrots, potato tubers, 

 alfalfa, and asparagus, but it appears to be identical with the Rhizoctonia 

 solani type which forms the sclerotia on the potato in Europe and 

 America. These two fungi when studied on the same host differ in the 

 character of the disease produced, in their appearance on the plants, and 

 in the histological relation of the parasite and host. The two are so 

 distinct in these characters on both the beet and the potato that it seems 

 impossible for one who has seen both types to confuse them. The cul- 

 tural relations of the two are also distinctly different. Rhizoctonia solani 

 is readily cultivated on a variety of media, but all attempts to put 



